Marijuana Botany by Robert Connel Clark

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Marijuana Botany

An Advanced Study: The Propagation and Breeding of Distinctive Cannabis

by Robert Connell Clarke

Introduction

Cannabis, commonly known in the United States as marijuana, is a wondrous plant an ancient plant and an ally of humanity for over ten thousand years. The pro-found impact Cannabis has had on the development andspread of civilization and conversely, the profound effectswe've had on the plant's evolution are just now beingdiscovered. Cannabis was one of the earliest and most importantplants placed under cultivation by prehistoric Asianpeoples. Virtually every part of the plant is usable. Fromthe stem comes hemp, a very long, strong fiber used tomake rope, cloth, and paper renowned for durability. Thedried leaves and flowers become the euphoriant, marijuana,and along with the root, are also used for numerous medi-cines. The seeds were a staple food in ancient China, one oftheir major "grains." Cannabis seeds are somewhat unpala-table and are now cultivated mainly for oil or for animalfeed. The oil is similar to linseed and is used for paint andvarnish making, fuel, and lubrication. Cultivated Cannabis quickly spread westward from itsnative Asia and by Roman times hemp was grown in almostevery European country. In Africa, marijuana was the pre-ferred product, smoked both ritually and for pleasure.When the first colonists came to America they, quitenaturally, brought hemp seed with them for rope andhome-spun cloth. Hemp fiber for ships' rigging was so im-portant to the English navy that colonists were paid boun-ties to grow hemp and in some states, penalties wereimposed on those who didn't. Prior to the Civil War, thehemp industry was second only to cotton in the South. Today, Cannabis grows around the world and is, infact, considered the most widely distributed of all culti-vated plants, a testimony to the plant's tenacity and adapt-able nature as well as to its usefulness and economic value.Unlike many plants, Cannabis never lost the ability toflourish without human help despite, perhaps, six millenniaof cultivation. Whenever ecological circumstances permit, the plantsreadily "escape" cultivation by becoming weedy and estab-lishing "wild" populations. Weedy Cannabis, descendedfrom the bygone hemp industry, grows in all but the morearid areas of the United States. Unfortunately, these weedsusually make a very poor grade marijuana. Such an adaptable plant, brought to a wide range ofenvironments, and cultivated and bred for a multitude ofproducts, understandably evolved a great number of dis-tinctive strains or varieties, each one uniquely suited tolocal needs and growing conditions. Many of these varietiesmay be lost through extinction and hybridization unless aconcerted effort is made to preserve them. This book pro-vides the basis for such an undertaking. There are likely more varieties of marijuana beinggrown or held as seeds in this country than any other.While traditional marijuana growers in Asia and Africa,typically, grow the same, single variety their forebearsgrew, American growers seek and embrace varieties fromall parts of the world. Very potent, early-flowering varietiesare especially prized because they can complete maturationeven in the northernmost states. The Cannabis stock in theUnited Nations seed bank is at best, depleted and in dis-array. American growers are in the best position to preventfurther loss of valuable varieties by saving, cataloguing, andpropagating their seeds. Marijuana Botany-the Propagation and Breeding ofDistinctive Cannabis is an important and most welcomebook. Its main thrust is the presentation of the scientificand horticultural principles, along with their practical ap-plications, necessary for the breeding and propagation ofCannabis and in particular, marijuana. This book will appealnot only to the professional researcher, but to the mari-juana enthusiast or anyone with an eye to the future ofCannabis products. To marijuana growers who wish to improve or up-grade their varieties, the book is an invaluable reference.Basic theories and practices for breeding pure stock orhybrids, cloning, grafting, or breeding to improve qualities such as potency or yield, are covered in a clear, easy-to-follow text which is liberally complemented with draw-ings, charts, and graphs by the author. Rob Clarke'sdrawings reflect his love of Cannabis. They sensitivelycapture the plant's elegance and ever-changing beauty whilebeing always informative and accurately rendered. The reader not familiar with botanical terms need notbe intimidated by a quick glance at the text. All terms aredefined when they are introduced and there is also a glos-sary with definitions geared to usage. Anyone familiar withthe plant will easily adopt the botanical terms. Years from now, many a marijuana smoker may un-knowingly be indebted to this book for the exotic varietiesthat will be preserved and new ones that will be developed.Growers will especially appreciate the expert informationon marijuana propagation and breeding so attractively andclearly presented.

Mel Frank author, Marijuana Growers' Guide
 
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Preface

Turn again our captivity, 0 Lord,as the streams in the dry land.They that sow in tears shall reap in joy.He that goeth forth and weepeth,bearing precious seed,shall doubtless come again with rejoicing,bringing his sheaves with him.-Psalms 126: 4-6 Cannabis is one of the world's oldest cultivated plants.Currently, however, Cannabis cultivation and use is illegalor legally restricted around the globe. Despite constantofficial control, Cannabis cultivation and use has spreadto every continent and nearly every nation. Cultivated andwild Cannabis flourishes in temperate and tropical climatesworldwide. Three hundred million users form a strong un-dercurrent beneath the flowing tide of eradication. Tojudge by increasing official awareness of the economicpotentials of Cannabis, legalization seems inevitable al-though slow. Yet as Cannabis faces eventual legalization itis threatened by extinction. Government-sanctioned and-supported spraying with herbicides and other forms oferadication have chased ancient Cannabis strains from theirnative homes. Cannabis has great potential for many commercialuses. According to a recent survey of available research byTurner, Elsohly and Boeren (1980) of the Research Insti-tute of Pharmaceutical Sciences at the University of Missis-sippi, Cannabis contains 421 known compounds, and newones are constantly being discovered and reported. Withoutfurther understanding of the potentials of Cannabis as asource of fiber, fuel, food, industrial chemicals and medi-cine it seems thoughtless to support eradication campaigns. World politics also threaten Cannabis. Rural Cannabisfarming cultures of the Middle East, Southeast Asia, Central America and Mrica face political unrest and openaggression. Cannabis seeds cannot be stored forever. If theyare not planted and reproduced each year a strain could belost. Whales, big cats, and redwoods are all protected inpreserves established by national and international laws.Plans must also be implemented to protect Cannabis cul-tures and rare strains from certain extinction. Agribusiness is excited at the prospect of supplyingAmerica's 20 million Cannabis users with domesticallygrown commercial marijuana. As a result, development ofuniform patented hybrid strains by multinational agricul-tural firms is inevitable. The morality of plant patent lawshas been challenged for years. For humans to recombineand then patent the genetic material of another living or-ganism, especially at the expense of the original organism,certainly offends the moral sense of many concerned citi-zens. Does the slight recombination of a plant's geneticmaterial by a breeder give him the right to own that organ-ism and its offspring? Despite public resistance voiced byconservation groups, the Plant Variety Protection Act of1970 was passed and currently allows the patenting of 224vegetable crops. New amendments could grant patentholders exclusive rights for 18 years to distribute, import,export and use for breeding purposes their newly devel-oped strains. Similar conventions worldwide could furtherthreaten genetic resources. Should patented varieties ofCannabis become reality it might be illegal to grow anystrain other than a patented variety, especially for food ormedicinal uses. Limitations could also be imposed suchthat only low-THC strains would be patentable. This couldlead to restrictions on small-scale growing of Cannabis;commercial growers could not take the chance of straypollinations from private plots harming a valuable seedcrop. Proponents of plant patenting claim that patents willencourage the development of new varieties. In fact, patentlaws encourage the spread of uniform strains devoid of thegenetic diversity which allows improvements. Patent lawshave also fostered intense competition between breedersand the suppression of research results which if made pub-lic could speed crop improvement. A handful of large cor-porations hold the vast majority of plant patents. Theseconditions will make it impossible for cultivators of nativestrains to compete with agribusiness and could lead to thefurther extinction of native strains now surviving on smallfarms in North America and Europe. Plant improvementin itself presents no threat to genetic reserves. However,the support and spread of improved strains by large cor-porations could prove disastrous. Like most major crops, Cannabis originated outsideNorth America in still-primitive areas of the world. Thou-sands of years ago humans began to gather seeds from wildCannabis and grow them in fields alongside the first culti-vated food crops. Seeds from the best plants were saved forplanting the following season. Cannabis was spread by no-madic tribes and by trade between cultures until it now ap-pears in both cultivated and escaped forms in many nations.The pressures of human and natural selection have resultedin many distinct strains adapted to unique niches withinthe ecosystem. Thus, individual Cannabis strains possessunique gene pools containing great potential diversity. Inthis diversity lies the strength of genetic inheritance. Fromdiverse gene pools breeders extract the desirable traits in-corporated into new varieties. Nature also calls on the genepool to ensure that a strain will survive. As climate changesand stronger pests and diseases appear, Cannabis evolvesnew adaptations and defenses. Modern agriculture is already striving to change thisnatural system. When Cannabis is legalized, the breedingand marketing of improved varieties for commercial agri-culture is certain. Most of the areas suitable for commercialCannabis cultivation already harbor their own native strains.Improved strains with an adaptive edge will follow in thewake of commercial agriculture and replace rare nativestrains in foreign fields. Native strains will hybridize withintroduced strains through wind-borne pollen dispersal andsome genes will be squeezed from the gene pool. Herein lies extreme danger! Since each strain of Can-nabis is genetically unique and contains at least a few genesnot found in other strains, if a strain becomes extinct theunique genes are lost forever. Should genetic weaknessesarise from excessive inbreeding of commercial strains, newvarieties might not be resistant to a previously unrecog-nized environmental threat. A disease could spread rapidlyand wipe out entire fields simultaneously. Widespread cropfailure would result in great financial loss to the farmer andpossible extinction of entire strains. In 1970, to the horror of American farmers and plantbreeders, Southern corn leaf-blight (Helm in thosporiummaydis) spread quickly and unexpectedly throughout corncrops and caught farmers off guard with no defense.H. maydis is a fungus which causes minor rot and damagein corn and had previously had no economic impact. How-ever, in 1969 a virulent mutant strain of the fungus ap-peared in Illinois, and by the end of the following seasonits wind-borne spores had spread and blighted crops fromthe Great Lakes to the Gulf of Mexico. Approximately15% of America's corn crop was destroyed. In some statesover half the crop was lost. Fortunately the only fields badly infected were thosecontaining strains descended from parents of what cornbreeders called "the Texas strain." Plants descended fromparents of previously developed strains were only slightlyinfected. The discovery and spread of the Texas strain hadrevolutionized the corn industry.
 
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Since pollen from this strain is sterile, female plants do not have to be detasseled by hand or machine, saving farmers millions of dollars annually. Unknown to corn breeders, hidden in this improved strain was an extreme vulnerability to the mutant leaf blight fungus. Total disaster was avoided by the around the clockefforts of plant breeders to develop a commercial strainfrom other than Texas plants. It still took three years todevelop and reproduce enough resistant seed to supply allwho needed it. We are also fortunate that corn breederscould rise to the challenge and had maintained seed reserves for breeding. If patented hybrid strains of Cannabisare produced and gain popularity, the same situation couldarise. Many pathogens are known to infect Cannabis andany one of them has the potential to reach epidemic pro-portions in a genetically uniform crop. We can not and should not stop plant improvement programs and the use of hybrid strains. However, we should provide a reserve of genetic material in case it is required in the future. Breeders can only combat future problems by relying on primitive gene pools contained in native strains. If native gene pools have been squeezed out by competition from patented commercial hybrids than the breeder is helpless. The forces of mutation and natural selection take thousands of years to modify gene pools, while a Cannabis blight could spread like wildfire. As Cannabis conservationists, we must fight the further amendment of plant patent laws to include Cannabis, and initiate programs immediately to collect, catalogue, and propagate vanishing strains. Cannabis preserves are needed where each strain can be freely cultivated in areas resemb-ling native habitats. This will help reduce the selective pressure of an introduced environment, and preserve thegenetic integrity of each strain. Presently such a program isfar from becoming a reality and rare strains are vanishing faster than they can be saved. Only a handful of dedicated researchers, cultivators, and conservationists are concerned with the genetic fate of Cannabis. It is tragic that a plantwith such promise should be caught up in an age when extinction at the hands of humans is common place. Responsibility is left with the few who will have the sensitivity to end genocide and the foresight to preserve Cannabis forfuture generations. Marijuana Botany presents the scientific knowledge and propagation techniques used to preserve and multiply vanishing Cannabis strains. Also included is information concerning Cannabis genetics and breeding used to beginplant improvement programs. It is up to the individual touse this information thoughtfully and responsibly.
 
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Chapter 1 - Sinsemilla Life Cycle of Cannabis
Cannabis is a tall, erect, annual herb.
Provided with an open sunny environment,
light well-drained composted soil, and ample
irrigation, Cannabis can grow to a height of
6 meters (about 20 feet) in a 4-6 month
growing season. Exposed river banks, mead-
ows, and agricultural lands are ideal habi-
tats for Cannabis since all offer good sun-
light. In this example an imported seed
from Thailand is grown without pruning
and becomes a large female plant. A cross
with a cutting from a male plant of Mexi-
can origin results in hybrid seed which is
stored for later planting. This example is
representative of the outdoor growth of
Cannabis in temperate climates.
Seeds are planted in the spring and
usually germinate in 3 to 7 days. The seed-
ling emerges from the ground by the
straightening of the hypocotyl (embryonic
stem). The cotyledons (seed leaves) are
slightly unequal in size, narrowed to the
base and rounded or blunt to the tip.
The hypocotyl ranges from 1 to 10
centimeters (1A to 3 inches) in length. About
10 centimeters or less above the cotyledons,
the first true leaves arise, a pair of oppo-
sitely oriented single leaflets each with a
distinct petiole (leaf stem) rotated one-
quarter turn from the cotyledons. Subse-
quent pairs of leaves arise in opposite
formation and a variously shaped leaf se-
quence develops with the second pair of
leaves having 3 leaflets, the third 5 and so
on up to 11 leaflets. Occasionally the first
pair of leaves will have 3 leaflets each rather
than 1 and the second pair, 5 leaflets each.
If a plant is not crowded, limbs will
grow from small buds (located at the inter-
section of petioles) along the main stem.
Each sinsemilla (seedless drug Cannabis)
plant is provided with plenty of room to
grow long axial limbs and extensive fine
roots to increase floral production. Under
favorable conditions Cannabis grows up to
7 centimeters (21A inches) a day in height
during the long days of summer.
Cannabis shows a dual response to
daylength; during the first two to three
months of growth it responds to increasing
daylength with more vigorous growth, but
in the same season the plant requires shorter
days to flower and complete its life cycle.
LIFE CYCLE OF CANNABIS I Juvenile Stage
Cannabis flowers when exposed to a
critical daylength which varies with the
strain. Critical daylength applies only to
plants which fail to flower under continu-
ous illumination, since those which flower
under continuous illumination have no criti-
cal daylength. Most strains have an absolute
requirement of inductive photoperiods
(short days or long nights) to induce fertile
flowering and less than this will result in
the formation of undifferentiated primor-
dia (unformed flowers) only.
The time taken to form primordia
varies with the length of the inductive pho- -
toperiod. Given 10 hours per day of light a
strain may only take 10 days to flower,
whereas if given 16 hours per day it may
take up to 90 days. Inductive photoperiods
of less than 8 hours per day do not seem to
accelerate primordia formation. Dark
(night) cycles must be uninterrupted to in-
duce flowering (see appendix).
Cannabis is a dioecious plant, which
means that the male and female flowers
develop on separate plants, although mono-
ecious examples with both sexes on one
plant are found. The development of
branches containing flowering organs varies
greatly between males and females: the
male flowers hang in long, loose, multi-
branched, clustered limbs up to 30 centi-
meters (12 inches) long, while the female
flowers are tightly crowded between small
leaves.
Note: Female Cannabis flowers and
plants will be referred to as pistillate and
male flowers and plants will be referred to
as staminate in the remainder of this text.
This convention is more accurate and makes
examples of complex aberrant sexuality
easier to understand.
The first sign of flowering in Cannabis
is the appearance of undifferentiated flower
primordia along the main stem at the nodes
(intersections) of the petiole, behind the
stipule (leaf spur). In the prefloral phase,
the sexes of Cannabis are indistinguishable
except for general trends in shape.
When the primordia first appear they
are undifferentiated sexually, but soon the
males can be identified by their curved
claw shape, soon followed by the differen-
tiation of round pointed flower buds having
five radial segments. The females are recog-
nized by the enlargement of a symmetrical
tubular calyx (floral sheath). They are easier
to recognize at a young age than male pri-
mordia. The first female calyxes tend to
lack paired pistils (pollen-catching appen-
dages) though initial male flowers often
mature and shed viable pollen. In some in-
dividuals, especially hybrids, small non-
flowering limbs will form at the nodes and
are often confused with male primordia.
Cultivators wait until actual flowers form
to positively determine the sex of Cannabis
The female plants tend to be shorter
and have more branches than the male.
Female plants are leafy to the top with
many leaves surrounding the flowers, while
male plants have fewer leaves near the top
with few if any leaves along the extended
flowering limbs.
 
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*The term pistil has developed a special meaning
with respect to Cannabis which differs slightly
from the precise botanical definition. This has
come about mainly from the large number of culti-
vators who have casual knowledge of plant anatomy
but an intense interest in the reproduction of Can-
nabis. The precise definition of pistil refers to the
combination of ovary, style and stigma. In the
more informal usage, pistil refers to the fused style
and stigma. The informal sense is used throughout
the book since it has become common practice
among Cannabis cultivators.
The female flowers appear as two long
white, yellow, or pink pistils protruding
from the fold of a very thin membranous
calyx. The calyx is covered with resin-
exuding glandular trichomes (hairs). Pistil-
late flowers are borne in pairs at the nodes
one on each side of the petiole behind the
stipule of bracts (reduced leaves) which
conceal the flowers. The calyx measures 2
to 6 millimeters in length and is closely
applied to, and completely contains, the
ovary.
In male flowers, five petals (approxi-
mately 5 millimeters, or 3/16 inch, long)
make up the calyx and may be yellow,
white, or green in color. They hang down,
and five stamens (approximately 5 milli-
meters long) emerge, consisting of slender
anthers (pollen sacs), splitting upwards from
the tip and suspended on thin filaments.
The exterior surface of the staminate calyx
is covered with non-glandular trichomes.
The pollen grains are nearly spherical
slightly yellow, and 25 to 30 microns (p)
in diameter. The surface is smooth and ex-
hibits 2 to 4 germ pores.
Before the start of flowering, the
phyllotaxy (leaf arrangement) reverses and
the number of leaflets per leaf decreases
until a small single leaflet appears below
each pair of calyxes. The phyllotaxy also
changes from decussate (opposite) to alter-
nate (staggered) and usually remains alter-
nate throughout the floral stages regardless
of sexual type.
The differences in flowering patterns
of male and female plants are expressed in
many ways. Soon after dehiscence (pollen
shedding) the staminate plant dies, while
the pistillate plant may mature up to five
months after viable flowers are formed if
little or no fertilization occurs. Compared
with pistillate plants, staminate plants show
a more rapid increase in height and a more
rapid decrease in leaf size to the bracts
which accompany the flowers. Staminate
plants tend to flower up to one month ear-
lier than pistillate plants; however, pistillate
plants often differentiate primordia one to
two weeks before staminate plants.
Many factors contribute to determin-
ing the sexuality of a flowering Cannabis
plant. Under average conditions with a nor-
mal inductive photoperiod, Cannabis will
bloom and produce approximately equal
numbers of pure staminate and pure pistil-
late plants with a few hermaphrodites (both
sexes on the same plant). Under conditions
of extreme stress, such as nutrient excess or
deficiency, mutilation, and altered light
cycles, populations have been shown to de-
part greatly from the expected one-to-one
staminate to pistillate ratio.
Just prior to dehiscence, the pollen
nucleus divides to produce a small repro-
ductive cell accompanied by a large vegeta-
tive cell, both of which are contained
within the mature pollen grain. Germina-
tion occurs 15 to 20 minutes after contact
with a pistil. As the pollen tube grows the
vegetative cell remains in the pollen grain
while the generative cell enters the pollen
tube and migrates toward the ovule. The
generative cell divides into two gametes
(sex cells) as it travels the length of the
pollen tube.
Pollination of the pistillate flower re-
sults in the loss of the paired pistils and a
swelling of the tubular calyx where the
ovule is enlarging. The staminate plants die
after shedding pollen. After approximately
14 to 35 days the seed is matured and drops
from the plant, leaving the dry calyx at-
tached to the stem. This completes the nor-
mally 4 to 6 month life cycle, which may
take as little as 2 months or as long as 10
months. Fresh seeds approach 100% viabil-
ity, but this decreases with age.
The hard mature seed is partially sur-
rounded by the calyx and is variously pat-
terned in grey, brown, or black. Elongated
and slightly compressed, it measures 2 to 6
millimeters (1/16 to 3/16 inch) in length
and 2 to 4 millimeters (1/16 to 1/8 inch) in
maximum diameter
Careful closed pollinations of a few
selected limbs yield hundreds of seeds of
known parentage, which are removed after
they are mature and beginning to fall from
the calyxes. The remaining floral clusters
are sinsemilla or seedless and continue to
mature on the plant. As the unfertilized
calyxes swell, the glandular trichomes on
the surface grow and secrete aromatic THC-
laden resins. The mature, pungent, sticky
floral clusters are harvested, dried, and
sampled. The preceding simplified life cycle
of sinsemilla Cannabis exemplifies the pro-
duction of valuable seeds without compro-
mising the production of seedless floral
clusters.
 
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Make the most of the Indian Hemp Seed and
sow it every where.
-George Washington

Chapter 2 - Propagation of Cannabis
Sexual versus Asexual Propagation
Cannabis can be propagated either sexually or asexu-
ally. Seeds are the result of sexual propagation. Because
sexual propagation involves the recombination of genetic
material from two parents we expect to observe variation
among seedlings and offspring with characteristics differing
from those of the parents. Vegetative methods of propaga-
tion (cloning) such as cuttage, layerage, or division of roots
are asexual and allow exact replication of the parental
plant without genetic variation. Asexual propagation, in
theory, allows strains to be preserved unchanged through
many seasons and hundreds of individuals.
When the difference between sexual and asexual prop-
agation is well understood then the proper method can be
chosen for each situation. The unique characteristics of a
plant result from the combination of genes in chromosomes
present in each cell, collectively known as the genotype of
that individual. The expression of a genotype, as influenced
by the environment, creates a set of visible characteristics
that we collectively term the phenotype. The function of
propagation is to preserve special genotypes by choosing
the proper technique to ensure replication of the desired
characteristics.
If two clones from a pistillate Cannabis plant are
placed in differing environments, shade and sun for in-
stance, their genotypes will remain identical. However, the
clone grown in the shade will grow tall and slender and
mature late, while the clone grown in full sun will remain
short and bushy and mature much earlier.
Sexual Propagation
Sexual propagation requires the union of staminate
pollen and pistillate ovule, the formation of viable seed,
and the creation of individuals with newly recombinant
genotypes. Pollen and ovules are formed by reduction divi-
sions (meiosis) in which the 10 chromosome pairs fail to
replicate, so that each of the two daughter-cells contains
one-half of the chromosomes from the mother cell. This is
known as the haploid (in) condition where in = 10 chro-
mosomes. The diploid condition is restored upon fertiliza-
tion resulting in diploid (2n) individuals with a haploid set
of chromosomes from each parent. Offspring may resemble
the staminate, pistillate, both, or neither parent and con-
siderable variation in offspring is to be expected. Traits
may be controlled by a single gene or a combination of
genes, resulting in further potential diversity.
The terms homozygous and heterozygous are useful
in describing the genotype of a particular plant. If the
genes controlling a trait are the same on one chromosome
as those on the opposite member of the chromosome pair
(homologous chromosomes), the plant is homozygous and
will "breed true" for that trait if self-pollinated or crossed
with an individual of identical genotype for that trait. The
traits possessed by the homozygous parent will be trans-
mitted to the offspring, which will resemble each other and
the parent. If the genes on one chromosome differ from
the genes on its homologous chromosome then the plant
is termed heterozygous; the resultant offspring may not
possess the parental traits and will most probably differ
from each other. Imported Cannabis strains usually exhibit
great seedling diversity for most traits and many types will
be discovered.
To minimize variation in seedlings and ensure preser-
vation of desirable parental traits in offspring, certain care-
ful procedures are followed as illustrated in Chapter III.
The actual mechanisms of sexual propagation and seed
production will be thoroughly explained here.
The Life Cycle and Sinsemilla Cultivation
A wild Cannabis plant grows from seed to a seedling,
to a prefloral juvenile, to either pollen- or seed-bearing
adult, following the usual pattern of development and
sexual reproduction. Fiber and drug production both inter-
fere with the natural cycle and block the pathways of
inheritance. Fiber crops are usually harvested in the juve-
nile or prefloral stage, before viable seed is produced,
while sinsemilla or seedless marijuana cultivation eliminates
pollination and subsequent seed production. In the case of
cultivated Cannabis crops, special techniques must be used
to produce viable seed for the following year without
jeopardizing the quality of the final product.
 
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Modern fiber or hemp farmers use commercially pro-
duced high fiber content strains of even maturation. Mono-
ecious strains are often used because they mature more
evenly than dioecious strains. The hemp breeder sets up
test plots where phenotypes can be recorded and controlled
crosses can be made. A farmer may leave a portion of his
crop to develop mature seeds which he collects for the fol-
lowing year. If a hybrid variety is grown, the offspring will
not ail resemble the parent crop and desirable character-
istics may be lost.
Growers of seeded marijuana for smoking or hashish
production collect vast quantities of seeds that fall from
the flowers during harvesting, drying, and processing. A
mature pistillate plant can produce tens of thousands of
seeds if freely pollinated. Sinsemilla marijuana is grown by
removing all the staminate plants from a patch, eliminating
every pollen source, and allowing the pistillate plants to
produce massive clusters of unfertilized flowers.
Various theories have arisen to explain the unusually
potent psychoactive properties of unfertilized Cannabis.
In general these theories have as their central theme the
extraordinarily long, frustrated struggle of the pistillate
plant to reproduce, and many theories are both twisted and
romantic. What actually happens when a pistillate plant
remains unfertilized for its entire life and how this ulti-
mately affects the cannabinoid (class of molecules found
only in Cannabis) and terpene (a class of aromatic organic
compounds) levels remains a mystery. It is assumed, how-
ever, that seeding cuts the life of the plant short and THC
(tetrahydrocannabinol the major psychoactive compound
in Cannabis) does not have enough time to accumulate.
Hormonal changes associated with seeding definitely affect
all metabolic processes within the plant including canna-
binoid biosynthesis. The exact nature of these changes is
unknown but probably involves imbalance in the enzymatic
systems controlling cannabinoid production. Upon fertili-
zation the plant's energies are channeled into seed produc-
tion instead of increased resin production. Sinsemilla plants
continue to produce new floral clusters until late fail, while
seeded plants cease floral production. It is also suspected
that capitate-stalked trichome production might cease
when the calyx is fertilized. If this is the case, then sinse-
milla may be higher in THC because of uninterrupted floral
growth, trichome formation and cannabinoid production.
What is important with respect to propagation is that once
again the farmer has interfered with the life cycle and no
naturally fertilized seeds have been produced.
The careful propagator, however, can produce as
many seeds of pure types as needed for future research
without risk of pollinating the precious crop. Staminate
parents exhibiting favorable characteristics are reproduc-
tively isolated while pollen is carefully collected and
applied to only selected flowers of the pistillate parents.
Many cultivators overlook the staminate plant, con-
sidering it useless if not detrimental. But the staminate
plant contributes half of the genotype expressed in the
offspring. Not only are staminate plants preserved for
breeding, but they must be allowed to mature, uninhibited,
until their phenotypes can be determined and the most
favorable individuals selected. Pollen may also be stored
for short periods of time for later breeding. Biology of Pollination
Pollination is the event of pollen landing on a stig-
matic surface such as the pistil, and fertilization is the
union of the staminate chromosomes from the pollen with
the pistillate chromosomes from the ovule.
Pollination begins with dehiscence (release of pollen)
from staminate flowers. Millions of pollen grains float
through the air on light breezes, and many land on the
stigmatic surfaces of nearby pistillate plants. If the pistil is
ripe, the pollen grain will germinate and send out a long
pollen tube much as a seed pushes out a root. The tube
contains a haploid (in) generative nucleus and grows
downward toward the ovule at the base of the pistils.
When the pollen tube reaches the ovule, the staminate
haploid nucleus fuses with the pistillate haploid nucleus
and the diploid condition is restored. Germination of the
pollen grain occurs 15 to 20 minutes after contact with
the stigmatic surface (pistil); fertilization may take up to
two days in cooler temperatures. Soon after fertilization,
the pistils wither away as the ovule and surrounding calyx
begin to swell. If the plant is properly watered, seed will
form and sexual reproduction is complete. It is crucial that
no part of the cycle be interrupted or viable seed will not
form. If the pollen is subjected to extremes of tempera-
ture, humidity, or moisture, it will fail to germinate, the
pollen tube will die prior to fertilization, or the embryo
will be unable to develop into a mature seed. Techniques
for successful pollination have been designed with all these
criteria in mind.
Controlled versus Random Pollinations
The seeds with which most cultivators begin represent
varied genotypes even when they originate from the same
floral cluster of marijuana, and not all of these genotypes
will prove favorable. Seeds collected from imported ship-
ments are the result of totally random pollinations among
many genotypes. If elimination of pollination was at-
tempted and only a few seeds appear, the likelihood is very
high that these pollinations were caused by a late flowering
staminate plant or a hermaphrodite, adversely affecting the
genotype of the offspring. Once the offspring of imported
strains are in the hands of a competent breeder, selection
and replication of favorable phenotypes by controlled
breeding may begin. Only one or two individuals out of
many may prove acceptable as parents. If the cultivator
allows random pollination to occur again, the population
not only fails to improve, it may even degenerate through
natural and accidental selection of unfavorable traits. We
must therefore turn to techniques of controlled pollination
by which the breeder attempts to take control and deter-
mine the genotype of future offspring.
Data Collection
Keeping accurate notes and records is a key to suc-
cessful plant-breeding. Crosses among ten pure strains (ten
staminate and ten pistillate parents) result in ten pure and
ninety hybrid crosses. It is an endless and inefficient task
to attempt to remember the significance of each little num-
ber and colored tag associated with each cross. The well-
organized breeder will free himself from this mental burden
and possible confusion by entering vital data about crosses,
phenotypes, and growth conditions in a system with one
number corresponding to each member of the population.
The single most important task in the proper collec-
tion of data is to establish undeniable credibility. Memory
fails, and remembering the steps that might possibly have
led to the production of a favorable strain does not con-
stitute the data needed to reproduce that strain. Data is
always written down; memory is not a reliable record. A
record book contains a numbered page for each plant, and
each separate cross is tagged on the pistillate parent and
recorded as follows: "seed of pistillate parent X pollen or
staminate parent." Also the date of pollination is included
and room is left for the date of seed harvest. Samples of
the parental plants are saved as voucher specimens for later
characterization and analysis.
Pollination Techniques
Controlled hand pollination consists of two basic
steps: collecting pollen from the anthers of the staminate
parent and applying pollen to the receptive stigmatic sur-
faces of the pistillate parent. Both steps are carefully con-
trolled so that no pollen escapes to cause random pollina-
tions. Since Cannabis is a wind-pollinated species, enclo-
sures are employed which isolate the ripe flowers from
wind, eliminating pollination, yet allowing enough light
penetration and air circulation for the pollen and seeds to
develop without suffocating. Paper and very tightly woven
cloth seem to be the most suitable materials.
 
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Coarse cloth
allows pollen to escape and plastic materials tend to col-
lect transpired water and rot the flowers. Light-colored
opaque or translucent reflective materials remain cooler in
the sun than dark or transparent materials, which either
absorb solar heat directly or create a greenhouse effect,
heating the flowers inside and killing the pollen. Pollina-
tion bags are easily constructed by gluing together vege-
table parchment (a strong breathable paper for steaming
vegetables) and clear nylon oven bags (for observation win-
dows) with silicon glue. Breathable synthetic fabrics such
as Gore-Tex are used with great success. Seed production
requires both successful pollination and fertilization, so the
conditions inside the enclosures must remain suitable for
pollen-tube growth and fertilization. It is most convenient
and effective to use the same enclosure to collect pollen
and apply it, reducing contamination during pollen trans-
fer. Controlled "free" pollinations may also be made if
only one pollen parent is allowed to remain in an isolated
area of the field and no pollinations are caused by her-
maphrodites or late-maturing staminate plants. If the
selected staminate parent drops pollen when there are only
a few primordial flowers on the pistillate seed parent, then
only a few seeds will form in the basal flowers and the rest
of the flower cluster will be seedless. Early fertilization
might also help fix the sex of the pistillate plant, helping
to prevent hermaphrodism. Later, hand pollinations can be
performed on the same pistillate parent by removing the
early seeds from each limb to be re-pollinated, so avoiding
confusion. Hermaphrodite or monoecious plants may be
isolated from the remainder of the population and allowed
to freely self-pollinate if pure-breeding offspring are desired
to preserve a selected trait. Selfed hermaphrodites usually
give rise to hermaphrodite offspring.
Pollen may be collected in several ways. If the propa-
gator has an isolated area where staminate plants can grow
separate from each other to avoid mutual contamination
and can be allowed to shed pollen without endangering
the remainder of the population, then direct collection
may be used. A small vial, glass plate, or mirror is held
beneath a recently-opened staminate flower which appears
to be releasing pollen, and the pollen is dislodged by tap-
ping the anthers. Pollen may also be collected by placing
whole limbs or clusters of staminate flowers on a piece of
paper or glass and allowing them to dry in a cool, still
place. Pollen will drop from some of the anthers as they
dry, and this may be scraped up and stored for a short time
in a cool, dark, dry spot. A simple method is to place the
open pollen vial or folded paper in a larger sealable con-
tamer with a dozen or more fresh, dry soda crackers or a
cup of dry white rice. The sealed container is stored in the
refrigerator and the dry crackers or rice act as a desiccant,
absorbing moisture from the pollen.
Any breeze may interfere with collection and cause
contamination with pollen from neighboring plants. Early
morning is the best time to collect pollen as it has not been
exposed to the heat of the day. All equipment used for col-
lection, including hands, must be cleaned before continuing
to the next pollen source. This ensures protection of each
pollen sample from contamination with pollen from differ-
ent plants.
Staminate flowers will often open several hours before
the onset of pollen release. If flowers are collected at this
time they can be placed in a covered bottle where they will open and release pollen within two days. A carefully sealed
paper cover allows air circulation, facilitates the release of
pollen, and prevents mold.
Both of the previously described methods of pollen
collection are susceptible to gusts of wind which may cause
contamination problems if the staminate pollen plants
grow at all close to the remaining pistillate plants. There-
fore, a method has been designed so that controlled pollen
collection and application can be performed in the same
area without the need to move staminate plants from their
original location. Besides the advantages of convenience,
the pollen parents mature under the same conditions
as the seed parents, thus more accurately expressing their
phenotypes.
The first step in collecting pollen is, of course, the
selection of a staminate or pollen parent. Healthy individ-
uals with well-developed clusters of flowers are chosen.
The appearance of the first staminate primordia or male
sex signs often brings a feeling of panic ("stamenoia") to
the cultivator of seedless Cannabis, and potential pollen
parents are prematurely removed. Staminate primordia
need to develop from one to five weeks before the flowers
open and pollen is released. During this period the selected
pollen plants are carefully watched, daily or hourly if neces-
sary, for developmental rates vary greatly and pollen may
be released quite early in some strains. The remaining
staminate plants that are unsuitable for breeding are de-
stroyed and the pollen plants specially labeled to avoid
confusion and extra work.
As the first flowers begin to swell, they are removed
prior to pollen release and destroyed. Tossing them on the
ground is ineffective because they may release pollen as
they dry. When the staminate plant enters its full floral
condition and more ripe flowers appear than can be easily
controlled, limbs with the most ripe flowers are chosen. It
is usually safest to collect pollen from two limbs for each
intended cross, in case one fails to develop. If there are ten
prospective seed parents, pollen from twenty limbs on the
pollen parent is collected. In this case, the twenty most-
flowered limb tips are selected and all the remaining flow-
ering clusters on the plant are removed to prevent stray
pollinations. Large leaves are left on the remainder of the
plant but are removed at the limb tips to minimize conden-
sation of water vapor released inside the enclosure. The
portions removed from the pollen parent are saved for
later analysis and phenotype characterization.
The pollination enclosures are secured and the plant
is checked for any shoots where flowers might develop
outside the enclosure. The completely open enclosure is
slipped over the limb tip and secured with a tight but
stretchable seal such as a rubber band, elastic, or plastic
plant tie-tape to ensure a tight seal and prevent crushing of
the vascular tissues of the stem. String and wire are
avoided. If enclosures are tied to weak limbs they may be
supported; the bags will also remain cooler if they are
shaded. Hands are always washed before and after handling
each pollen sample to prevent accidental pollen transfer
and contamination.
Enclosures for collecting and applying pollen and
preventing stray pollination are simple in design and con-
struction. Paper bags make convenient enclosures. Long
narrow bags such as light-gauge quart-bottle bags, giant
popcorn bags or bakery bags provide a convenient shape
for covering the limb tip. The thinner the paper used the
more air circulation is allowed, and the better the flowers
will develop. Very thick paper or plastic bags are never
used. Most available bags are made with water soluble glue
and may come apart after rain or watering. All seams are
sealed with waterproof tape or silicon glue and the bags
should not be handled when wet since they tear easily.
Bags of Gore-Tex cloth or vegetable parchment will not
tear when wet. Paper bags make labeling easy and each bag
is marked in waterproof ink with the number of the indi-
vidual pollen parent, the date and time the enclosure was
secured, and any useful notes. Room is left to add the date
of pollen collection and necessary information about the
future seed parent it will pollinate.
Pollen release is fairly rapid inside the bags, and after
two days to a week the limbs may be removed and dried in
a cool dark place, unless the bags are placed too early or
the pollen parent develops very slowly. To inspect the
progress of pollen release, a flashlight is held behind the
bag at night and the silhouettes of the opening flowers are
easily seen. In some cases, clear nylon windows are in-
stalled with silicon glue for greater visibility. When flower-
ing is at its peak and many flowers have just opened,
collection is completed, and the limb, with its bag attached,
is cut. If the limb is cut too early, the flowers will not have
shed any pollen; if the bag remains on the plant too long,
most of the pollen will be dropped inside the bag where
heat and moisture will destroy it. When flowering is at its
peak, millions of pollen grains are released and many more
flowers will open after the limbs are collected. The bags are
collected early in the morning before the sun has time to
heat them up. The bags and their contents are dried in a
cool dark place to avoid mold and pollen spoilage. If pollen
becomes moist, it will germinate and spoil, therefore dry
storage is imperative.
 
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After the staminate limbs have dried and pollen re-
lease has stopped, the bags are shaken vigorously, allowed
to settle, and carefully untied. The limbs and loose flowers
are removed, since they are a source of moisture that
could promote mold growth, and the pollen bags are re-
sealed. The bags may be stored as they are until the seed
parent is ready for pollination, or the pollen may be re-
moved and stored in cool, dry, dark vials for later use and
hand application. Before storing pollen, any other plant
parts present are removed with a screen. A piece of fuel
filter screening placed across the top of a mason jar works
well, as does a fine-mesh tea strainer.
Now a pistillate plant is chosen as the seed parent. A
pistillate flower cluster is ripe for fertilization so long as
pale, slender pistils emerge from the calyxes. Withered,
dark pistils protruding from swollen, resin encrusted ca-
lyxes are a sign that the reproductive peak has long passed.
Cannabis plants can be successfully pollinated as soon as
the first primordia show pistils and until just before har-
vest, but the largest yield of uniform, healthy seeds is
achieved by pollinating in the peak floral stage. At this
time, the seed plant is covered with thick clusters of white
pistils. Few pistils are brown and withered, and resin pro-
duction has just begun. This is the most receptive time for
fertilization, still early in the seed plant's life, with plenty
of time remaining for the seeds to mature. Healthy, well-
flowered lower limbs on the shaded side of the plant are
selected. Shaded buds will not heat up in the bags as much
as buds in the hot sun, and this will help protect the sensi-
tive pistils. When possible, two terminal clusters of pistillate
flowers are chosen for each pollen bag. In this way, with
two pollen bags for each seed parent and two clusters of
pistillate flowers for each bag, there are four opportunities
to perform the cross successfully. Remember that produc
tion of viable seed requires successful pollination, fertiliza-
tion and embryo development. Since interfering with any
part of this cycle precludes seed development, fertilization
failure is guarded against by duplicating all steps.
Before the pollen bags are used, the seed parent infor-
mation is added to the pollen parent data. Included is the
number of the seed parent, the date of pollination, and any
comments about the phenotypes of both parents. Also, for
each of the selected pistillate clusters, a tag containing the
same information is made and secured to the limb below
the closure of the bag. A warm, windless evening is chosen
for pollination so the pollen tube has time to grow before
sunrise. After removing most of the shade leaves from the
tips of the limbs to be pollinated, the pollen is tapped away
from the mouth of the bag. The bag is then carefully
opened and slipped over two inverted limb tips, taking care
not to release any pollen, and tied securely with an ex-
pandable band. The bag is shaken vigorously, so the pollen
will be evenly dispersed throughout the bag, facilitating
complete pollination. Fresh bags are sometimes used, either
charged with pollen prior to being placed over the limb tip,
or injected with pollen, using a large syringe or atomizer,
after the bag is placed. However, the risk of accidental
pollination with injection is higher.
If only a small quantity of pollen is available it may
be used more sparingly by diluting with a neutral powder
such as flour before it is used. When pure pollen is used,
many pollen grains may land on each pistil when only one
is needed for fertilization. Diluted pollen will go further
and still produce high fertilization rates. Diluting 1 part
pollen with 10 to 100 parts flour is common. Powdered
fungicides can also be used since this helps retard the
growth of molds in the maturing, seeded, floral clusters.
The bags may remain on the seed parent for some
time; seeds usually begin to develop within a few days, but
their development will be retarded by the bags. The propa-
gator waits three full sunny days, then carefully removes
and sterilizes or destroys the bags. This way there is little
chance of stray pollination. Any viable pollen that failed
to pollinate the seed parent will germinate in the warm
moist bag and die within three days, along with many of
the unpollinated pistils. In particularly cool or overcast
conditions a week may be necessary, but the bag is re-
moved at the earliest safe time to ensure proper seed devel-
opment without stray pollinations. As soon as the bag is
removed, the calyxes begin to swell with seed, indicating
successful fertilization. Seed parents then need good irriga-
tion or development will be retarded, resulting in small,
immature, and nonviable seeds. Seeds develop fastest in
warm weather and take usually from two to four weeks to
mature completely. In cold weather seeds may take up to
two months to mature. If seeds get wet in fall rains, they
may sprout. Seeds are removed when the calyx begins to
dry up and the dark shiny perianth (seed coat) can be seen
protruding from the drying calyx. Seeds are labeled and
stored in a cool, dark, dry place,
This is the method employed by breeders to create
seeds of known parentage used to study and improve Can-
nabis genetics. Seed Selection
Nearly every cultivated Cannabis plant, no matter
what its future, began as a germinating seed; and nearly all
Cannabis cultivators, no matter what their intention, start
with seeds that are gifts from a fellow cultivator or ex-
tracted from imported shipments of marijuana. Very little
true control can be exercised in seed selection unless the
cultivator travels to select growing plants with favorable
characteristics and personally pollinate them. This is not
possible for most cultivators or researchers and they usually
rely on imported seeds.
 
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cannebosanac

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These seeds are of unknown par-
entage, the product of natural selection or of breeding by
the original farmer, Certain basic problems affect the
genetic purity and predictability of collected seed.
1 - If a Cannabis sample is heavily seeded, then the
majority of the male plants were allowed to mature and
release pollen, Since Cannabis is wind-pollinated, many
pollen parents (including early and late maturing stami-
nate and hermaphrodite plants) will contribute to the seeds
in any batch of pistillate flowers. If the seeds are all taken
from one flower cluster with favorable characteristics, then
at least the pistillate or seed parent is the same for all those
seeds, though the pollen may have come from many differ-
ent parents. This creates great diversity in offspring.
2 - In very lightly seeded or nearly sinsemilla Can-
nabis, pollination has largely been prevented by the removal
of staminate parents prior to the release of pollen. The few
seeds that do form often result from pollen from hermaph-
rodite plants that went undetected by the farmer, or by
random wind-borne pollen from wild plants or a nearby
field. Hermaphrodite parents often produce hermaphrodite
offspring and this may not be desirable.
3 - Most domestic Cannabis strains are random hy-
brids. This is the result of limited selection of pollen par-
ents, impure breeding conditions, and lack of adequate
space to isolate pollen parents from the remainder of the
crop.
When selecting seeds, the propagator will frequently
look for seed plants that have been carefully bred locally
by another propagator. Even if they are hybrids there is a
better chance of success than with imported seeds, pro-
vided certain guidelines are followed:
1 - The dried seeded flower clusters are free of
staminate flowers that might have caused hermaphrodite
pollinations.
2 - The flowering clusters are tested for desirable
traits and seeds selected from the best.
3 - Healthy, robust seeds are selected. Large, dark
seeds are best; smaller, paler seeds are avoided since these
are usually less mature and less viable.
4 - If accurate information is not available about the
pollen parent, then selection proceeds on common sense
and luck. Mature seeds with dried calyxes in the basal por-
tions of the floral clusters along the main stems occur in
the earliest pistillate flowers to appear and must have been
pollinated by early-maturing pollen parents. These seeds
have a high chance of producing early-maturing offspring.
By contrast, mature seeds selected from the tips of floral
clusters, often surrounded by immature seeds, are formed
in later-appearing pistillate flowers. These flowers were
likely pollinated by later-maturing staminate or hermaphro-
dite pollen parents, and their seeds should mature later and
have a greater chance of producing hermaphrodite off-
spring. The pollen parent also exerts some influence on the
appearance of the resulting seed. If seeds are collected
from the same part of a flower cluster and selected for
similar size, shape, color, and perianth patterns, then it is
more likely that the pollinations represent fewer different
gene pools and will produce more uniform offspring.
5 - Seeds are collected from strains that best suit the
locality; these usually come from similar climates and lati-
tudes. Seed selection for specific traits is discussed in detail
in Chapter III.
6 - Pure strain seeds are selected from crosses between
parents of the same origin.
7 - Hybrid seeds are selected from crosses between
pure strain parents of different origins.
8 - Seeds from hybrid plants, or seeds resulting from
pollination by hybrid plants, are avoided, since these will
not reliably reproduce the phenotype of either parent.
Seed stocks are graded by the amount of control ex-
erted by the collector in selecting the parents.
Grade #1 - Seed parent and pollen parent are known and
there is absolutely no possibility that the seeds resulted
from pollen contamination.
Grade #2 - Seed parent is known but several known stami-
nate or hemaphrodite pollen parents are involved.
Grade #3 - Pistillate parent is known and pollen parents
are unknown.
Grade #4 - Neither parent is known, but the seeds are col-
lected from one floral cluster, so the pistillate seed parent-
age traits may be characterized.
Grade #5 - Parentage is unknown but origin is certain,
such as seeds collected from the bottom of a bag of im-
ported Cannabis.
Grade #6 - Parentage and origin are unknown. Asexual Propagation
Asexual propagation (cloning) allows the preservation
of genotype because only normal cell division (mitosis)
occurs during growth and regeneration. The vegetative
(non-reproductive) tissue of Cannabis has 10 pairs of
chromosomes in the nucleus of each cell. This is known as
the diploid (2n) condition where 2n = 20 chromosomes.
During mitosis every chromosome pair replicates and one
of the two identical sets of chromosome pairs migrates to
each daughter cell, which now has a genotype identical to
the mother cell. Consequently, every vegetative cell in a
Cannabis plant has the same genotype and a plant resulting
from asexual propagation will have the same genotype as
the mother plant and will, for all practical purposes, de-
velop identically under the same environmental conditions.
 
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cannebosanac

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In Cannabis, mitosis takes place in the shoot apex
(meristem), root tip meristems, and the meristematic cam-
bium layer of the stalk. A propagator makes use of these
meristematic areas to produce clones that will grow and be
multiplied. Asexual propagation techniques such as cuttage,
layerage, and division of roots can ensure identical popula-
tions as large as the growth and development of the paren-
tal material will permit. Clones can be produced from even
a single cell, because every cell of the plant possesses the
genetic information necessary to regenerate a complete
plant.
Asexual propagation produces clones which perpetu-
ate the unique characteristics of the parent plant. Because
of the heterozygous nature of Cannabis, valuable traits
may be lost by sexual propagation that can be preserved
and multiplied by cloning. Propagation of nearly identical
populations of all-pistillate, fast growing, evenly maturing
Cannabis is made possible through cloning. Any agricul-
tural or environmental influences will affect all the mem-
bers of that clone equally.
The concept of clone does not mean that all members
of the clone will necessarily appear identical in all charac-
teristics. The phenotype that we observe in an individual is
influenced by its surroundings. Therefore, members of the
clone will develop differently under varying environmental
conditions. These influences do not affect genotype and
therefore are not permanent. Cloning theoretically can pre-
serve a genotype forever. Vigor may slowly decline due to
poor selection of clone material or the constant pressure
of disease or environmental stress, but this trend will re-
verse if the pressures are removed. Shifts in genetic compo-
sition occasionally occur during selection for vigorous
growth. However, if parental strains are maintained by in-
frequent cloning this is less likely. Only mutation of a gene
in a vegetative cell that then divides and passes on the mu-
tated gene will permanently affect the genotype of the
clone. If this mutated portion is cloned or reproduced
sexually, the mutant genotype will be further replicated.
Mutations in clones usually affect dominance relations and
are therefore noticed immediately. Mutations may be in-
duced artificially (but without much predictability) by
treating meristematic regions with X-rays, colchicine, or
other mutagens.
The genetic uniformity provided by clones offers a
control for experiments designed to quantify the subtle
effects of environment and cultural techniques. These
subtleties are usually obscured by the extreme diversity
resulting from sexual propagation. However, clonal uni-
formity can also invite serious problems. If a population of
clones is subjected to sudden environmental stress, pests, or
disease for which it has no defense, every member of the
clone is sure to be affected and the entire population may
be lost. Since no genetic diversity is found within the
clone, no adaptation to new stresses can occur through
recombination of genes as in a sexually propagated
population.
In propagation by cuttage or layerage it is only neces-
sary for a new root system to form, since the meristematic
shoot apex comes directly from the parental plant. Many
stem cells, even in mature plants, have the capability of
producing adventitious roots. In fact, every vegetative cell
in the plant contains the genetic information needed for an
entire plant. Adventitious roots appear spontaneously from
stems and old roots as opposed to systemic roots which
appear along the developing root system originating in the
embryo. In humid conditions (as in the tropics or a green-
house) adventitious roots occur naturally along the main
stalk near the ground and along limbs where they droop
and touch the ground.
Rooting
A knowledge of the internal structure of the stem is
helpful in understanding the origin of adventitious roots.
The development of adventitious roots can be broken
down into three stages: (1) the initiation of meristematic
cells located just outside and between the vascular bundles
(the root initials), (2) the differentiation of these meristem-
atic cells into root primordia, and (3) the emergence and
growth of new roots by rupturing old stem tissue and
establishing vascular connections with the shoot.
As the root initials divide, the groups of cells take on
the appearance of a small root tip. A vascular system forms
with the adjacent vascular bundles and the root continues
to grow outward through the cortex until the tip emerges
from the epidermis of the stem. Initiation of root growth
usually begins within a week and young roots appear within
four weeks. Often an irregular mass of white cells, termed
callus tissue, will form on the surface of the stem adjacent
to the areas of root initiation. This tissue has no influence
on root formation. However, it is a form of regenerative
tissue and is a sign that conditions are favorable for root
initiation.
The physiological basis for root initiation is well un-
derstood and allows many advantageous modifications of
rooting systems. Natural plant growth substances such as
auxins, cytokinins, and gibberellins are certainly responsible
for the control of root initiation and the rate of root for-
mation. Auxins are considered the most influential. Auxins
and other growth substances are involved in the control of
virtually all plant processes: stem growth, root formation,
lateral bud inhibition, floral maturation, fruit development,
and determination of sex. Great care is exercised in appli-
cation of artificial growth substances so that detrimental
conflicting reactions in addition to rooting do not occur.
Auxins seem to affect most related plant species in the
same way, but the mechanism of this action is not yet
fully understood.
 
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Many synthetic compounds have been shown to have
auxin activity and are commercially available, such as
napthaleneacetic acid (NAA), indolebutyric acid (IBA),
and 2,4-dichlorophenoxyacetic acid (2,4 DPA), but only
indoleacetic acid has been isolated from plants. Naturally
occurring auxin is formed mainly in the apical shoot men-
stem and young leaves. It moves downward after its forma-
tion at the growing shoot tip, but massive concentrations
of auxins in rooting solutions will force travel up the vas-
cular tissue. Knowledge of the physiology of auxins has
led to practical applications in rooting cuttings. It was
shown originally by Went and later by Thimann and Went
that auxins promote adventitious root formation in stem
cuttings. Since application of natural or synthetic auxin
seems to stimulate adventitious root formation in many
plants, it is assumed that auxin levels are associated with
the formation of root initials. Further research by Warmke
and Warmke (1950) suggested that the levels of auxin
may determine whether adventitious roots or shoots are
formed, with high auxin levels promoting root growth and
low levels favoring shoots.
Cytokinins are chemical compounds that stimulate
cell growth. In stem cuttings, cytokinins suppress root
growth and stimulate bud growth. This is the opposite of
the reaction caused by auxins, suggesting that a natural
balance of the two may be responsible for regulating nor-
mal plant growth. Skoog discusses the use of solutions
of equal concentrations of auxins and cytokinins to pro-
mote the growth of undifferentiated callus tissues. This
may provide a handy source of undifferentiated material
for cellular cloning.
Although Cannabis cuttings and layers root easily,
variations in rootability exist and old stems may resist
rooting. Selection of rooting material is highly important.
Young, firm, vegetative shoots, 3 to 7 millimeters (1/8 to
1/4 inch) in diameter, root most easily. Weak, unhealthy
plants are avoided, along with large woody branches and
reproductive tissues, since these are slower to root. Stems
of high carbohydrate content root most easily. Firmness is
a sign of high carbohydrate levels in stems but may be con-
fused with older woody tissue. An accurate method of de-
termining the carbohydrate content of cuttings is the
iodine starch test. The freshly cut ends of a bundle of
cuttings are immersed in a weak solution of iodine in
potassium iodide. Cuttings containing the highest starch
content stain the darkest; the samples are rinsed and sorted
accordingly. High nitrogen content cuttings seem to root
more poorly than cuttings with medium to low nitrogen
content. Therefore, young, rapidly-growing stems of high
nitrogen and low carbohydrate content root less well than
slightly older cuttings. For rooting, sections are selected
that have ceased elongating and are beginning radial growth.
Staminate plants have higher average levels of carbohydrates
than pistillate plants, while pistillate plants exhibit higher
nitrogen levels. It is unknown whether sex influences root-
ing, but cuttings from vegetative tissue are taken just after
sex determination while stems are still young. For rooting
cloning stock or parental plants, the favorable balance (low
nitrogen-to-high carbohydrate) is achieved in several ways:
1 - Reduction of the nitrogen supply will slow shoot
growth and allow time for carbohydrates to accumulate.
This can be accomplished by leaching (rinsing the soil with
large amounts of fresh water), withholding nitrogenous
fertilizer, and allowing stock plants to grow in full sun-
light. Crowding of roots reduces excessive vegetative
growth and allows for carbohydrate accumulation.
2 - Portions of the plant that are most likely to root
are selected. Lower branches that have ceased lateral
growth and begun to accumulate starch are the best. The
carbohydrate-to-nitrogen ratio rises as you move away
from the tip of the limb, so cuttings are not made too short.
3 - Etiolation is the growth of stem tissue in total
darkness to increase the possibility of root initiation.
Starch levels drop, strengthening tissues and fibers begin to
soften, cell wall thickness decreases, vascular tissue is
diminished, auxin levels rise, and undifferentiated tissue
begins to form. These conditions are very conducive to the
initiation of root growth. If the light cycle can be con-
trolled, whole plants can be subjected to etiolation, but
usually single limbs are selected for cloning and wrapped
for several inches just above the area where the cutting
will be taken. This is done two weeks prior to rooting. The
etiolated end may then be unwrapped and inserted into
the rooting medium. Various methods of layers and
cuttings rooted below soil level rely in part on the effects
of etiolation.
4 - Girdling a stem by cutting the phloem with a
knife or crushing it with a twisted wire may block the
downward mobility of carbohydrates and auxin and root-
ing cofactors, raising the concentration of these valuable
components of root initiation above the girdle. Making Cuttings
Cuttings of relatively young vegetative limbs 10 to 45
centimeters (4 to 18 inches) are made with a sharp knife or
razor blade and immediately placed in a container of clean,
pure water so the cut ends are well covered. It is essential
that the cuttings be placed in water as soon as they are
removed or a bubble of air (embolism) may enter the cut
end and block the transpiration stream in the cutting,
causing it to wilt. Cuttings made under water avoid the
possibility of an embolism. If cuttings are exposed to the
air they are cut again before being inserted into the rooting
medium.
The medium should be warm and moist before cut-
tings are removed from the parental plant. Rows of holes
are made in the rooting medium with a tapered stick,
slightly larger in diameter than the cutting, leaving at least
10 centimeters (4 inches) between each hole. The cuttings
are removed from the water, the end to be rooted treated
with growth regulators and fungicides (such as Rootone F
or Hormex), and each cutting placed in its hole. The cut
end of the shoot is kept at least 10 centimeters (4 inches)
from the bottom of the medium. The rooting medium is
lightly tamped around the cutting, taking care not to
scrape off the growth regulators. During the first few days
the cuttings are checked frequently to make sure every-
thing is working properly. The cuttings are then watered
with a mild nutrient solution once a day.
Hardening-off
 
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The cuttings usually develop a good root system and
will be ready to transplant in three to six weeks. At this
time the hardening-off process begins, preparing the deli-
cate cuttings for a life in bright sunshine. The cuttings are
removed and transplanted to a sheltered spot such as a
greenhouse until they begin to grow on their own. It is
necessary to water them with a dilute nutrient solution or
feed with finished compost as soon as the hardening-off
process begins. Young roots are very tender and great care
is necessary to avoid damage. When vegetative cuttings are
placed outside under the prevailing photoperiod they will
react accordingly. If it is not the proper time of the year
for the cuttings to grow and mature properly (near harvest
time, for example) or if it is too cold for them to be put
out, then they may be kept in a vegetative condition by
supplementing their light to increase daylength. Alterna-
tively they may be induced to flower indoors under arti-
ficial conditions. After shoots are selected and prepared for cloning,
they are treated and placed in the rooting medium. Since
the discovery in 1984 that auxins such as IAA stimulate
the production of adventitious roots, and the subsequent
discovery that the application of synthetic auxins such as
NAA increase the rate of root production, many new tech-
niques of treatment have appeared. It has been found that
mixtures of growth regulators are often more effective
than one alone. IAA and NAA a--e often combined with a
small percentage of certain phenoxy compounds and fungi-
cides in commercial preparations. Many growth regulators
deteriorate rapidly, and fresh solutions are made up as
needed. Treatments with vitamin B1 (thiamine) seem to
help roots grow, but no inductive effect has been noticed.
As soon as roots emerge, nutrients are necessary; the shoot
cannot maintain growth for long on its own reserves. A
complete complement of nutrients in the rooting medium
certainly helps root growth; nitrogen is especially bene-
ficial. Cuttings are extremely susceptible to fungus attack,
and conditions conducive to rooting are also favorable to
the growth of fungus. "Cap tan " is a long-lasting fungicide
that is sometimes applied in powdered form along with
growth regulators. This is done by rolling the basal end of
the cutting in the powder before placing it in the rooting
medium.
Oxygen and Rooting
The initiation and growth of roots depends upon
atmospheric oxygen. If oxygen levels are low, shoots may
fail to produce roots and rooting will certainly be inhibited.
It is very important to select a light, well-aerated rooting
medium. In addition to natural aeration from the atmos-
phere, rooting media may be enriched with oxygen (02)
gas; enriched rooting solutions have been shown to increase
rooting in many plant species. No threshold for damage by
excess oxygenation has been determined, although exces-
sive oxygenation could displace carbon dioxide which is
also vital for proper root initiation and growth. If oxygen
levels are low, roots will form only near the surface of the
medium, whereas with adequate oxygen levels, roots will
tend to form along the entire length of the implanted
shoot, especially at the cut end.
Oxygen enrichment of rooting media is fairly simple.
Since shoot cuttings must be constantly wetted to ensure
proper rooting, aeration of the rooting media may be facili-
tated by aerating the water used in irrigation. Mist systems
achieve this automatically because they deliver a fine mist
(high in dissolved oxygen) to the leaves, from where much
of it runs off into the soil, aiding rooting. Oxygen enrich-
ment of irrigation water is accomplished by installing an
aerator in the main water line so that atmospheric oxygen
can be absorbed by the water. An increase in dissolved
oxygen of only 20 parts per million may have a great in-
fluence on rooting. Aeration is a convenient way to add
oxygen to water as it also adds carbon dioxide from the
atmosphere. Air from a small pump or bottled oxygen may
also be supplied directly to the rooting media through tiny
tubes with pin holes, or through a porous stone such as
those used to aerate aquariums.
Rooting Media
Water is a common medium for rooting. It is inexpen-
sive, disperses nutrients evenly, and allows direct observa-
tion of root development. However, several problems arise.
A water medium allows light to reach the submerged stem,
delaying etiolation and slowing root growth. Water also
promotes the growth of water molds and other fungi, sup-
ports the cutting poorly, and restricts air circulation to the
young roots. In a well aerated solution, roots will appear in
great profusion at the base of the stem, while in a poorly
aerated or stagnant solution only a few roots will form at
the surface, where direct oxygen exchange occurs. If root-
ings are made in pure water, the solution might be replaced
regularly with tap water, which should contain sufficient
oxygen for a short period. If nutrient solutions are used, a
system is needed to oxygenate the solution. The nutrient
solution does become concentrated by evaporation, and
this is watched. Pure water is used to dilute rooting solu-
tions and refill rooting containers.
Soil Treatment
Solid media provide anchors for cuttings, plenty of
darkness to promote etiolation and root growth, and suffi-
cient air circulation to the young roots. A high-quality soil
with good drainage such as that used for seed germination
is often used but the soil must be carefully sterilized to
prevent the growth of harmful bacteria and fungus. A small
amount of soil can easily be sterilized by spreading it out
on a cookie sheet and heating it in an oven set at "low,"
approximately 820 C (180~ F), for thirty minutes. This kills
most harmful bacteria and fungus as well as nematodes, in-
sects and most weed seeds. Overheating the soil will cause
the breakdown of nutrients and organic complexes and the
formation of toxic compounds. Large amounts of soil may
be treated by chemical fumigants. Chemical fumigation
avoids the breakdown of organic material by heat and may
result in a better rooting mix. Formaldehyde is an excellent
fungicide and kills some weed seeds, nematodes, and in-
sects. One gallon of commercial formalin (40% strength) is
mixed with 50 gallons of water and slowly applied until
each cubic foot of soil absorbs 2-4 quarts of solution.
Small containers are sealed with plastic bags; large flats and
plots are covered with polyethylene sheets. After 24 hours
the seal is removed and the soil is allowed to dry for two
weeks or until the odor of formaldehyde is no longer
present. The treated soil is drenched with water prior to
use. Fumigants such as formaldehyde, methyl bromide
or other lethal gases are very dangerous and cultivators
use them only outside with appropriate protection for
themselves.
 
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It is usually much simpler and safer to use an artificial
sterile medium for rooting. Vermiculite and perlite are
often used in propagation because of their excellent drain-
age and neutral pH (a balance between acidity and alkalin-
ity). No sterilization is needed because both products are
manufactured at high heat and contain no organic material.
It has been found that a mixture of equal portions of
medium and large grade vermiculite or perlite promotes the
greatest root growth. This results from increased air circu-
lation around the larger pieces. A weak nutrient solution,
including micro-nutrients, is needed to wet the medium,
because little or no nutrient material is supplied by these
artificial media. Solutions are checked for pH and cor-
rected to neutral with agricultural lime, dolomite lime, or
oyster shell lime.
Layering
Layering is a process in which roots develop on a
stem while it remains attached to, and nutritionally sup-
ported by the parent plant. The stem is then detached and
the meristematic tip becomes a new individual, growing
on its own roots, termed a layer. Layering differs from
cutting because rooting occurs while the shoot is still
attached to the parent. Rooting is initiated in layering by
various stem treatments which interrupt the downward
flow of photosynthates (products of photosynthesis) from
the shoot tip. This causes the accumulation of auxins,
carbohydrates and other growth factors. Rooting occurs in
this treated area even though the layer remains attached
to the parent. Water and mineral nutrients are supplied by
the parent plant because only the phloem has been inter-
rupted; the xylem tissues connecting the shoot to the
parental roots remain intact (see illus. 1, page 29). In this
manner, the propagator can overcome the problem of keep-
ing a severed cutting alive while it roots, thus greatly in-
creasing the chances of success. Old woody reproductive
stems that, as cuttings, would dry up and die, may be
rooted by layering. Layering can be very time-consuming
and is less practical for mass cloning of parental stock
than removing and rooting dozens of cuttings. Layering,
however, does give the small-scale propagator a high-success
alternative which also requires less equipment than cuttings.
Techniques of Layering
Almost all layering techniques rely on the principle of
etiolation. Both soil layering and air layering involve de-
priving the rooting portion of the stem of light, promoting
rooting. Root-promoting substances and fungicides prove
beneficial, and they are usually applied as a spray or pow-
der. Root formation on layers depends on constant mois-
ture, good air circulation and moderate temperatures at
the site of rooting.
Soil Layering
Soil layering may be performed in several ways. The
most common is known as tip layering. A long, supple
vegetative lower limb is selected for layering, carefully bent
so it touches the ground, and stripped of leaves and small
shoots where the rooting is to take place. A narrow trench,
6 inches to a foot long and 2 to 4 inches deep, is dug paral-
lel to the limb, which is placed along the bottom of the
trench, secured with wire or wooden stakes, and buried
with a small mound of soil. The buried section of stem
may be girdled by cutting, crushed with a loop of wire, or
twisted to disrupt the phloem tissue and cause the accumu-
lation of substances which promote rooting. It may also be
treated with growth regulators at this time.
Serpentine layering may be used to create multiple
layers along one long limb. Several stripped sections of the
limb are buried in separate trenches, making sure that at
least one node remains above ground between each set of
roots to allow shoots to develop. The soil surrounding the
stem is kept moist at all times and may require wetting
several times a day. A small stone or stick is inserted under
each exposed section of stem to prevent the lateral shoot
buds rotting from constant contact with the moist soil sur-
face. Tip layers and serpentine layers may be started in
small containers placed near the parental plant. Rooting
usually begins within two weeks, and layers may be re-
moved with a sharp razor or clippers after four to six
weeks. If the roots have become well established, trans-
planting may be difficult without damaging the tender root
system. Shoots on layers continue to grow under the same
conditions as the parent, and less time is needed for the
clone to acclimatize or harden-off and begin to grow on its
own than with cuttings.
 
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In air layering, roots form on the aerial portions of
stems that have been girdled, treated with growth regula-
tors, and wrapped with moist rooting media. Air layering
is an ancient form of propagation, possibly invented by the
Chinese. The ancient technique of goo tee uses a ball of clay
or soil plastered around a girdled stem and held with a
wrap of fibers. Above this is suspended a small container
of water (such as a bamboo section) with a wick to the
wrapped gootee; this way the gootee remains moist.
The single most difficult problem with air layers is the
tendency for them to dry out quickly. Relatively small
amounts of rooting media are used, and the position on
aerial parts of the plant exposes them to drying winds and
sun. Many wraps have been tried, but the best seems to be
clear polyethylene plastic sheeting which allows oxygen to
enter and retains moisture well. Air layers are easiest to
make in greenhouses where humidity is high, but they may
also be used outside as long as they are kept moist and
don't freeze. Air layers are most useful to the amateur
propagator and breeder because they take up little space
and allow the efficient cloning of many individuals. Making an Air Layer
A recently sexed young limb 3-10 mm (1/8 to 3/8
inch) in diameter is selected. The site of the layer is usually
a spot 30 centimeters (12 inches) or more from the limb
tip. Unless the stem is particularly strong and woody, it is
splinted by positioning a 30 centimeter (12 inch) stick of
approximately the same diameter as the stem to be layered
along the bottom edge of the stem. This splint is tied in
place at both ends with a piece of elastic plant-tie tape.
This enables the propagator to handle the stem more con-
fidently. An old, dry Cannabis stem works well as a splint.
Next, the stem is girdled between the two ties with a twist
of wire or a diagonal cut. After girdling, the stem is sprayed
or dusted with a fungicide and growth regulator, sur-
rounded with one or two handfuls of unmilled sphagnum
moss, and wrapped tightly with a small sheet of clear poly-
ethylene film (4-6 mil). The film is tied securely at each
end, tightly enough to make a waterproof seal but not so
tight that the phloem tissues are crushed. If the phloem is
crushed, compounds necessary for rooting will accumulate
outside of the medium and rooting will be slowed. Plastic
florist's tape or electrician's tape works well for sealing air
layers. Although polyethylene film retains moisture well,
the moss will dry out eventually and must be remoistened
periodically. Unwrapping each layer is impractical and
would disturb the roots, so a hypodermic syringe is used to
inject water, nutrients, fungicides, and growth regulators.
If the layers become too wet the limb rots. Layers are
checked regularly by injecting water until it squirts out
and then very lightly squeezing the medium to remove any
extra water. Heavy layers on thin limbs are supported by
tying them to a large adjacent limb or a small stick an-
chored in the ground. Rooting begins within two weeks
and roots will be visible through the clear plastic within
four weeks. When the roots appear adequately developed,
the layer is removed, carefully unwrapped, and trans-
planted with the moss and the splint intact. The layer is
watered well and placed in a shady spot for a few days to
allow the plant to harden-off and adjust to living on its
own root system. It is then placed in the open. In hot
weather, large leaves are removed from the shoot before
removing the layer to prevent excessive transpiration and
wilting.
Layers develop fastest just after sexual differentiation.
Many layers may be made of staminate plants in order to
save small samples of them for pollen collection and to
conserve space. By the time the pollen parents begin to
flower profusely, the layers will be rooted and may be cut
and removed to an isolated area. Layers taken from pistil-
late plants are used for breeding, or saved and cloned for
the following season.
 
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Layers often seem rejuvenated when they are re-
moved from the parent plant and begin to be supported by
their own root systems. This could mean that a clone will
continue to grow longer and mature later than its parent
under the same conditions. Layers removed from old or
seeded parents will continue to produce new calyxes and
pistils instead of completing the life cycle along with the
parents. Rejuvenated layers are useful for off-season seed
production. Grafting
Intergeneric grafts between Cannabis and Humulus
(hops) have fascinated researchers and cultivators for
decades. Warmke and Davidson (1943) claimed that Humu-
lus tops grafted upon Cannabis roots produced ". . . as
much drug as leaves from intact hemp plants, even though
leaves from intact hop plants are completely nontoxic."
According to this research, the active ingredient of Canna-
bis was being produced in the roots and transported across
the graft to the Hum ulus tops. Later research by Crombie
and Crombie (1975) entirely disproves this theory. Grafts
were made between high and low THC strains of Cannabis
as well as intergeneric grafts between Cannabis and Humu-
lus, Detailed chromatographic analysis was performed on
both donors for each graft and their control populations.
The results showed ". . . no evidence of transport of inter-
mediates or factors critical to cannabinoid formation
across the grafts."
Grafting of Cannabis is very simple. Several seedlings
can be grafted together into one to produce very interesting
specimen plants. One procedure starts by planting one seed-
ling each of several separate strains close together in the
same container, placing the stock (root plant) for the cross
in the center of the rest. When the seedlings are four weeks
old they are ready to be grafted. A diagonal cut is made
approximately half-way through the stock stem and one of
the scion (shoot) seedlings at the same level. The cut por-
tions are slipped together such that the inner cut surfaces
are touching. The joints are held with a fold of cellophane
tape. A second scion from an adjacent seedling may be
grafted to the stock higher up the stem. After two weeks,
the unwanted portions of the grafts are cut away. Eight to
twelve weeks are needed to complete the graft, and the
plants are maintained in a mild environment at all times.
As the graft takes, and the plant begins to grow, the tape
falls off.
Pruning
Pruning techniques are commonly used by Cannabis
cultivators to limit the size of their plants and promote
branching. Several techniques are available, and each has
its advantages and drawbacks. The most common method
is meristem pruning or stem tip removal. In this case the
growing tip of the main stalk or a limb is removed at
approximately the final length desired for the stalk or limb.
Below the point of removal, the next pair of axial growing
tips begins to elongate and form two new limbs. The
growth energy of one stem is now divided into two, and
the diffusion of growth energy results in a shorter plant
which spreads horizontally.
 
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Auxin produced in the tip meristem travels down the
stem and inhibits branching. When the meristem is re-
moved, the auxin is no longer produced and branching may
proceed uninhibited. Plants that are normally very tall and
stringy can be kept short and bushy by meristem pruning.
Removing meristems also removes the newly formed tissues
near the meristem that react to changing environmental
stimuli and induce flowering. Pruning during the early part
of the growth cycle will have little effect on flowering, but
plants that are pruned late in life, supposedly to promote
branching and floral growth, will often flower late or fail
to flower at all. This happens because the meristemic
tissue responsible for sensing change has been removed and
the plant does not measure that it is the time of the year
to flower. Plants will usually mature fastest if they are
allowed to grow and develop without interference from
pruning. If late maturation of Cannabis is desired, then
extensive pruning may work to delay flowering. This is
particularly applicable if a staminate plant from an early-
maturing strain is needed to pollinate a late-maturing pistil-
late plant. The staminate plant is kept immature until the
pistillate plant is mature and ready to be pollinated. When
the pistillate plant is receptive, the staminate plant is
allowed to develop flowers and release pollen.
Other techniques are available for limiting the size and
shape of a developing Cannabis plant without removing
meristematic tissues. Trellising is a common form of modi-
fication and is achieved in several ways. In many cases
space is available only along a fence or garden row. Posts 1
to 2 meters (3 to 6 feet) long may be driven into the
ground 1 to 3 meters (3 to 10 feet) apart and wires
stretched between them at 30 to 45 centimeters (12 to 18
inches) intervals, much like a wire fence or grape trellis.
Trellises are ideally oriented on an east-west axis for maxi-
mum sun exposure. Seedlings or pistillate clones are placed
between the posts, and as they grow they are gradually
bent and attached to the wire. The plant continues to grow
upward at the stem tips, but the limbs are trained to grow
horizontally. They are spaced evenly along the wires by
hooking the upturned tips under the wire when they are 15
to 30 centimeters (6 to 12 inches) long. The plant grows
and spreads for some distance, but it is never allowed to
grow higher than the top row of wire. When the plant be-
gins to flower, the floral clusters are allowed to grow up-
ward in a row from the wire where they receive maximum
sun exposure. The floral clusters are supported by the wire
above them, and they are resistant to weather damage.
Many cultivators feel that trellised plants, with increased
sun exposure and meristems intact, produce a higher
yield than freestanding unpruned or pruned plants. Other
growers feel that any interference with natural growth
patterns limits the ultimate size and yield of the plant.
 
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Another method of trellising is used when light expo-
sure is especially crucial, as with artificial lighting systems.
Plants are placed under a horizontal or slightly slanted flat
sheet of 2 to 5 centimeters (1 to 2 inches) poultry netting
which is suspended on a frame 30 to 60 centimeters (12 to
24 inches) from the soil surface perpendicular to the direc-
tion of incoming light or to the lowest path of the sun. The
seedlings or clones begin to grow through the netting al-'
most immediately, and the meristems are pushed back
down under the netting, forcing them to grow horizon-
tally outward. Limbs are trained so that the mature plant
will cover the entire frame evenly. Once again, when the
plant begins to flower, the floral clusters are allowed to
grow upward through the wire as they reach for the light.
This might prove to be a feasible commercial cultivation
technique, since the flat beds of floral clusters could be
mechanically harvested. Since no meristem tissues are re-
moved, growth and maturation should proceed on schedule.
This system also provides maximum light exposure for all
the floral clusters, since they are growing from a plane
perpendicular to the direction of light.
Sometimes limbs are also tied down, or crimped and
bent to limit height and promote axial growth without
meristem removal. This is a particularly useful technique
for greenhouse cultivation, where plants often reach the
roof or walls and burn or rot from the intense heat and
condensation of water on the inside of the greenhouse.
To prevent rotting and burning while leaving enough room
for floral clusters to form, the limbs are bent at least 60
centimeters (24 inches) beneath the roof of the green-
house. Tying plants over allows more light to strike the
plant, promoting axial growth. Crimping stems and bending
them over results in more light exposure as well as inhibit-
ing the flow of auxin down the stem from the tip. Once
again, as with meristem removal, this promotes axial
growth.
 
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Limbing is another common method of pruning Can-
nabis plants. Many small limbs will usually grow from the
bottom portions of the plant, and due to shading they re-
main small and fail to develop large floral clusters. If these
atrophied lower limbs are removed, the plant can devote
more of its floral energies to the top parts of the plant
with the most sun exposure and the greatest chance of
pollination. The question arises of whether removing entire
limbs constitutes a shock to the growing plant, possibly
limiting its ultimate size. It seems in this case that shock
is minimized by removing entire limbs, including propor-
tional amounts of stems, leaves, meristems, and flowers;
this probably results in less metabolic imbalance than if
only flowers, leaves, or meristems were removed. Also, the
lower limbs are usually very small and seem of little signifi-
cance in the metabolism of the total plant. In large plants,
many limbs near the central stalk also become shaded and
atrophied and these are also sometimes removed in an
effort to increase the yield of large floral clusters on the
sunny exterior margins.
Leafing is one of the most misunderstood techniques
of drug Cannabis cultivation. In the mind of the cultivator,
several reasons exist for removing leaves. Many feel that
large shade leaves draw energy from the flowering plant,
and therefore the flowering clusters will be smaller. It is
felt that by removing the leaves, surplus energy will be
available, and large floral clusters will be formed. Also,
some feel that inhibitors of flowering, synthesized in the
leaves during the long noninductive days of summer, may
be stored in the older leaves that were formed during the
noninductive photoperiod. Possibly, if these inhibitor-laden
leaves are removed, the plant will proceed to flower, and
maturation will be accelerated. Large leaves shade the inner
portions of the plant, and small atrophied floral clusters
may begin to develop if they receive more light. In actuality, few if any of the theories behind leafing
give any indication of validity. Indeed, leafing possibly
serves to defeat its original purpose. Large leaves have a
definite function in the growth and development of Can-
nabis. Large leaves serve as photosynthetic factories for the
production of sugars and other necessary growth sub-
stances. They also create shade, but at the same time they
are collecting valuable solar energy and producing foods
that will be used during the floral development of the
plant. Premature removal of leaves may cause stunting,
because the potential for photosynthesis is reduced. As
these leaves age and lose their ability to carry on photo-
synthesis they turn chloro tie (yellow) and fall to the
ground. In humid areas care is taken to remove the yellow
or brown leaves, because they might invite attack by fun-
gus. During chlorosis the plant breaks down substances,
such as chlorophylls, and translocates the molecular com-
ponents to a new growing part of the plant, such as the
flowers. Most Cannabis plants begin to lose their larger
leaves when they enter the flowering stage, and this trend
continues until senescence. It is more efficient for the plant
to reuse the energy and various molecular components of
existing chlorophyll than to synthesize new chlorophyll at
the time of flowering. During flowering this energy is
needed to form floral clusters and ripen seeds.
Removing large amounts of leaves may interfere with
the metabolic balance of the plant. If this metabolic change
occurs too late in the season it could interfere with floral
development and delay maturation. If any floral inhibitors
are removed, the intended effect of accelerating flowering
will probably be counteracted by metabolic upset in the
plant. Removal of shade leaves does facilitate more light
reaching the center of the plant, but if there is not enough
food energy produced in the leaves, the small internal
floral clusters will probably not grow any larger. Leaf re-
moval may also cause sex reversal resulting from a meta-
bolic change.
If leaves must be removed, the petiole is cut so that
at least an inch remains attached to the stalk. Weaknesses
in the limb axis at the node result if the leaves are pulled
off at the abscission layer while they are still green. Care is
taken to see that the shriveling petiole does not invite
fungus attack.
It should be remembered that, regardless of strain or
environmental conditions, the plant strives to reproduce,
and reproduction is favored by early maturation. This pro-
duces a situation where plants are trying to mature and
reproduce as fast as possible. Although the purpose of
leafing is to speed maturation, disturbing the natural pro-
gressive growth of a plant probably interferes with its rapid
development.
Cannabis grows largest when provided with plentiful
nutrients, sunlight, and water and left alone to grow and
mature naturally. It must be remembered that any altera-
tion of the natural life cycle of Cannabis will affect pro-
ductivity. Imaginative combinations and adaptations of
propagation techniques exist, based on specific situations
of cultivation. Logical choices are made to direct the
natural growth cycle of Cannabis to favor the timely
maturation of those products sought by the cultivator,
without sacrificing seed or clone production.
 
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Aktivan Član
13.10.2006
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Chapter 3 - Genetics and Breeding of Cannabis
The greatest service which can be rendered to any country is to add a useful plant to its culture.
-Thomas Jefferson

Genetics
Although it is possible to breed Cannabis with limited success without any knowledge of the laws of inheritance, the full potential of diligent breeding, and the line of action most likely to lead to success, is realized by breeders who have mastered a working knowledge of genetics.
As we know already, all information transmitted from generation to generation must be contained in the pollen of the staminate parent and the ovule of the pistillate parent. Fertilization unites these two sets of genetic information, a seed forms, and a new generation is begun. Both pollen and ovules are known as gametes, and the transmitted units determining the expression of a character are known as genes. Individual plants have two identical sets of
genes (2n) in every cell except the gametes, which through reduction division have only one set of genes (in). Upon fertilization one set from each parent combines to form a seed (2n).
In Cannabis, the haploid (in) number of chromosomes is 10 and the diploid (2n) number of chromosomes is 20. Each chromosome contains hundreds of genes, influencing every phase of the growth and development of the plant.
If cross-pollination of two plants with a shared genetic trait (or self-pollination of a hermaphrodite) results in offspring that all exhibit the same trait, and if all subsequent (inbred) generations also exhibit it, then we say that the strain (i.e., the line of offspring derived from common ancestors) is truebreeding, or breeds true, for that trait. A strain may breed true for one or more traits while varying in other characteristics. For example, the traits of sweet aroma and early maturation may breed true, while offspring vary in size and shape. For a strain to breed true for some trait, both of the gametes forming the offspring must have an identical complement of the genes that influence the expression of that trait. For example, in a strain that breeds true for webbed leaves, any gamete from any parent in that population will contain the gene for webbed leaves, which we will signify with the letter w. Since each gamete carries one-half (in) of the genetic complement of the offspring, it follows that upon fertilization both "leafshape" genes of the (2n) offspring will be w. That is, the offspring, like both parents, are ww. In turn, the offspring also breed true for webbed leaves because they have only w genes to pass on in their gametes.
On the other hand, when a cross produces offspring that do not breed true (i.e., the offspring do not all resemble their parents) we say the parents have genes that segregate or are hybrid. Just as a strain can breed true for one or more traits, it can also segregate for one or more traits; this is often seen. For example, consider a cross where some of the offspring have webbed leaves and some have normal compound-pinnate leaves. (To continue our
system of notation we will refer to the gametes of plants with compound-pinnate leaves as W for that trait. Since these two genes both influence leaf shape, we assume that they are related genes, hence the lower-case w and uppercase W notation instead of w for webbed and possibly P for
pinnate.) Since the gametes of a true-breeding strain must each have the same genes for the given trait, it seems logical that gametes which produce two types of offspring must have genetically different parents.
Observation of many populations in which offspring differed in appearance from their parents led Mendel to his theory of genetics. If like only sometimes produces like, then what are the rules which govern the outcome of these crosses? Can we use these rules to predict the outcome of
future crosses?
Assume that we separate two true-breeding populations of Cannabis, one with webbed and one with compound-pinnate leaf shapes. We know that all the gametes produced by the webbed-leaf parents will contain genes for leaf-shape w and all gametes produced by the compound-pinnate individuals will have W genes for leaf shape. (The offspring may differ in other characteristics, of course.)

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If we make a cross with one parent from each of the true-breeding strains, we will find that 100% of the offspring are of the compound-pinnate leaf phenotype. (The expression of a trait in a plant or strain is known as the phenotype.) What happened to the genes for webbed leaves contained in the webbed leaf parent? Since we know that there were just as many w genes as W genes combined in the offspring, the W gene must mask the expression of the w gene. We term the W gene the dominant gene and say that the trait of compound-pinnate leaves is dominant over the recessive trait of webbed leaves. This seems logical since the normal phenotype in Cannabis has compound-pinnate leaves. It must be remembered, however, that many useful traits that breed true are recessive. The true-breeding dominant or recessive condition, WW or ww, is termed the homozygous condition; the segregating hybrid condition wW or Ww is called heterozygous. When we cross two of the F1 (first filial generation) offspring resulting from the initial cross of the P1 (parental generation) we observe two types of offspring. The F2 generation shows a ratio of approximately 3:1, three compound pinnate type-to-one webbed type. It should be remembered that phenotype ratios are theoretical. The real results may vary from the expected ratios, especially in small samples.
In this case, compound-pinnate leaf is dominant over webbed leaf, so whenever the genes w and W are combined, the dominant trait W will be expressed in the phenotype. In the F2 generation only 25% of the offspring are homozygous for W so only 25% are fixed for W. The w trait is only expressed in the F2 generation and only when two w genes are combined to form a double-recessive, fixing the recessive trait in 25% of the offspring. If compound-pinnate showed incomplete dominance over webbed, the genotypes in this example would remain the same, but the phenotypes in the F1 generation would all be intermediate types resembling both parents and the F2 phenotype ratio would be 1 compound-pinnate :2 intermediate :1 webbed.