Marijuana Grower's Handbook

by Ed Rosenthal

  The word cannabis is an ancient one, dating back past Latin and Greek to Thracian or Scythian times. Scholars have even identified ancient Biblical references to a plant known as ‘kaneh-bos’ as early as the 15th century B.C.

  As the contemporary name of a type of plant, Cannabis Sativa Linnaeus (L.) was formally conferred in 1753 by Carolus Linnaeas in his famous taxonomy. Linnaeas, who devised the modern system for classifying and naming species, concluded that the genus Cannabis sativa had but one species, which bears the same botanical name. The genus is currently classified as belonging to the Cannabaceae family, which also includes hops (Humulus sp.). Modern phylogenetic studies and gene sequencing indicate that Cannabis sativa L. is more properly considered part of the Celtidaceae branch, which also includes the many species of Hackberrry tree, and that the two families should be merged to form a single group descended from a common ancestor. This would not be the first time that Cannabis sativa L. has been reclassified, as it was formerly categorized as part of the Nettle (Urticaceae) or Mulberry (Moraceae) family.

  There has been a similar evolution of thinking on how many species of Cannabis sativa L. should be recognized. In 1785, soon after Linnaeus identified it as a single species, the influential biologist Jean-Baptiste de Lamarck claimed the plant he found in India should be classified as a separate species, which he named Cannabis indica. This name would be included in various pharmacopoeias to designate cannabis plants that are suitable for the manufacture of medicinal preparations.

  In the 19th century, other botanists proposed separate species classifications for cannabis plants indigenous to China and Vietnam. But by the 20th century, difficulty with definitively distinguishing between any of them had led most botanists to conclude, as Linnaeus did, that all cannabis plants belong to a single species. Certainly all cannabis plants satisfy one of the chief criteria of a species: they can interbreed. There are different ways to define a species. Wide disparities in cannabis plants’ geographic location and primary characteristics have led many to argue that three species should be recognized, based on whether they are cultivated primarily for fiber (sativa) or drugs (indica), or grow wild (ruderalis).

  Cannabis ruderalis is probably the progenitor wild variety. The alleles or genetic traits of ruderlis are mostly dominant, indicating that the competing traits are probably mutations. For instance, flowering in ruderalis begins soon after germination and is not dependent on the length of daylight; this characteristic dominates crosses.

  1. Male flower bract

  2. Female flower bract

  3. Male flower

  4. Bunch of male flowers

  5. Unfertilized female flower

  6.-9. Maturing seed

  10. Mature seed in perianth

  11. Mature seed

  12. Cutaway of seed showing embryo

  SCIENTIFIC CLASSIFICATION

  Kingdom: Plantae

  Division: Magnoliophyta

  Class: Magnoliopsida

  Order: Rosales

  Family: Cannabaceae

  Genus: Cannabis

  Formal Botanical Description

  Cannabis is an annual, dioecious, flowering herb. The leaves have serrated leaflets. The first pair of leaves usually have a single leaflet, the number gradually increasing up to a maximum of about thirteen leaflets per leaf (usually seven or nine), depending on variety and growing conditions. At the top of a flowering plant, this number again diminishes to a single leaflet per leaf. The lower leaf pairs usually occur in an opposite leaf arrangement and the upper leaf pairs in an alternate arrangement on the main stem of a mature plant.

  Cannabis normally has imperfect flowers, with staminate “male” and pistillate “female” flowers occurring on separate plants. Occasionally, individual plants bear both male and female flowers. Although monoecious plants are often referred to as “hermaphrodites,” true hermaphrodites (which are less common) bear staminate and pistillate structures on individual flowers, whereas monoecious plants bear male and female flowers at different locations on the same plant.

  Cannabis is wind-pollinated and produces “seeds” that are technically called achenes. Most strains of Cannabis are short day plants, with the possible exception of C. ruderalis and some equatorial C. sativa varieties that are commonly described as “auto-flowering” and may be day-neutral. Cannabis is diploid, having a chromosome complement of 2n=20. Polyploid individuals have been artificially produced. Cannabis plants produce a group of chemicals called cannabinoids, which are secreted by glandular trichomes that occur most abundantly on the floral calyxes and bracts of female plants.

  The diversity of the cannabis plants’ geography and morphology is considerable; they grow in very different ways and places. The stems grow to a height between from 3’-15’ (0.9-4.5m) or more, and the plants range from thin and reedy to thick and bushy. While the plants are native to the Hindu Kush Valley and the Himalayan foothills, it has migrated with humans throughout the world and can now be found growing wild on every continent but Antarctica. Since there are no laws prohibiting it in Antarctica where researchers from many countries work, it is safe to assume that cannabis has spread its roots there, too.

  The Hindu-Kush region ranges through the Himalayan foothills and the southern stretch of the Tibetan Plateau which stretches thousands of miles from Kazakhstan through Tajikistan, Afghanistan, India, Nepal and Bhutan. South of the foothills, cannabis cultivation is practiced throughout India and Southeast Asia.

  Cannabis sativa L. is the only dioecious annual—that is, each plant is distinctively either male or female—though hermaphrodite plants do occur, producing both male and female flowers. Also unusual is the fact that cannabis is an annual yet its closest botanical relative, hops, is a perennial. That, combined with the cannabis plant’s ability in Nepal and similar climates to over winter or regenerate in spring, leads me to believe the plant’s evolutionary path from being a perennial to an annual was relatively recent.

  Even the plant’s iconic leaves, instantly recognizable even to those who have never seen a plant growing, come in very different sizes and subtly different shapes. The palmate leaves can range from a spread of a few inches (approx 5cm) to more than a foot, while the five to seven sharply serrated leaflets vary from long and thin to broad and stubby. The cannabis plant’s combination of extreme genetic variability and ease of interbreeding is part of what makes it so exciting to grow. The range of characteristics that selective breeding can produce is astonishing.

  THE HIGH

  The wide variety of looks, tastes, smells and highs of marijuana are no coincidence. The terrific subtleties of this plant allow gardeners with different goals to strive for their ideal plant. Marijuana enthusiasts have the pleasure of exploring the myriad effects, flavors, and odors that these varieties have to offer.

  We often hear that varieties of marijuana have different tastes and highs because they contain varying ratios of cannabinoids, the chemicals specific to marijuana. However, testing of most modern marijuana shows a big spike in delta-9 THC (Δ9-THC), but in most varieties all the other 100-odd cannabinoids—including cannabinol (CBN), cannabidiol (CBD), cannabichromene (CBC) and cannabigerol (CBG)—are scarcely noted. The most popular strains show a substantial percentage of THC, generally registering 15% to 20% of bud weight. Most marijuana garden books talk about how the cannabinoid known as cannabidiol (CBD) somehow mediates the psychoactive qualities of THC. And some studies have indicated that CBD may affect THC uptake in such a way as to reduce some negative psychological effects, such as anxiety. But in 2005, scientists determined that CBD does not dock at the CB1 receptor sites in the brain that THC targets.

  While the high is what most users notice, marijuana can have many other effects. Researchers have determined that the human body has a second type of cannabinoid receptor, named CB2, to which CBD binds. This may explain CBD’s many apparent medicinal qualities. For example, clinical trials on pain control indicate that a 50-50 mix of THC and CBD produce the best
analgesic effect. Similarly, the concentration of CB2 receptors in the human gut suggests that they may be responsible for marijuana’s well-documented ability to stimulate appetite, control nausea, and ease abdominal cramping. Much research remains to be done on the immune-modulating functions and other possible therapeutic applications of cannabinoids, including their possible role in fighting cancer tumors and controlling auto-immune malfunctions such as arthritis and Alzheimer’s.

  Since plants are not mobile, they can’t outrun predators or pick up and relocate when competing plants move into the neighborhood. As a result, they have amassed other defenses against predators and competitors. One of their main strategies is chemical warfare. They produce oils and other chemicals designed to repel enemies. Others kill, sicken, delay maturation or affect their metabolism. Plants use other aromatics to attract either pollinators for reproduction or predators that attack the plants’ enemies. THC and the terpenes were developed as part of this arsenal.

  If a recipe of cannabinoids doesn’t determine the personality of the high, what does? We can sniff out the answer. Experienced marijuana users often rate marijuana’s quality, before they ever use it, by simply smelling it. They may expect a certain kind of experience based on the odor. Interestingly enough, THC and the other cannabinoids are odorless. What these connoisseurs are smelling are terpenes, the essential oils of plants.

  TERPENES

  If cannabinoids, other than THC, are not contributing to the high, then we look at other ingredients in the smoke-stream.

  Terpenes are major components of marijuana resin, just as they make up the largest percentage of aromatic essential oils contained in most plants. The scent of most flowers, herbs and spices are composed of these oils. When therapists use plant oils in aromatherapy, or when you use natural incense, perfume, or other scent to set the mood, you are inhaling various combinations of terpenes. They have the power to take you up or down, help you relax or focus, feel anxious or satisfied.

  You recognize the presence of terpenes when you pinch that bud and take a whiff. Grapefruit, Silver Haze, Blueberry, Real Skunk—each of these odors brings a recognition of the type of high that the sample will explode into your brain.

  Plants produce terpenes for one of three reasons:

  •to attract pollinators

  •to repel or kill herbivores

  •to attract predators of herbivores

  These odor molecules, which are costly for the plant to produce, increase as the plant’s investment in reproduction increases. Before flowering, the odors are faint. As flowering progresses and the plant is more invested in protecting it, the odor grows. As the bud ripens, whether seeded or sinsemilla (unpollinated), the odor increases substantially. Marijuana is wind pollinated, so it doesn’t need to attract pollinators and outdoors it is resilient to insect predation as the odors are a signal to experienced mammals to stay away. This indicates that the odors deter animals that would eat the plant, including larger browsers.

  By temporarily altering brain function, terpenes affect mood, sensitivity, and perceptions, including balance and pain.

  Chemically speaking, terpenes are composed of repeating units of isoprene, which is a five-carbon unit chain or ring with eight hydrogen atoms attached (C5H8). Terpenes use the simple isoprene units as blocks to build molecules with 10, 15, 20, 30, and 40 carbon units; they also twist and turn the molecular structure to form simple chains or three-dimensional (polycyclic) structures. Most significantly for the marijuana plant, terpene pathways are key enzymatic steps in the plant’s production of THC. In addition, terpenes can form bonds with other molecules which affect how animals and plants react to them. Depending on how terpenes stack against each other, they create different aromas.

  As it matures sexually, marijuana produces terpenes in the glands that surround the flowers. Terpene levels increase during the dark period and reach their peak just before dawn. During the day they evaporate and fill the surrounding air with odor to warn predators. By the end of the day, at dusk, terpene (and cannabinoid) levels are at their lowest.

  Most of the aromas that we associate with plants are the result of terpenes and flavonoids. Humans can smell and taste these compounds, but that is not the only way they affect us. Aromatherapy uses the inhalation of essential oils to regulate mood, sleep patterns, acuity, and healing processes. For example, lavender oil is a soothing agent and relaxant; rosemary is used to focus attention and provide a sense of satisfaction. These effects are a result of the combination of terpenes and other chemicals found in the oils of these plants. While terpenes affect the brain in their own way, they also modify the effect of THC within the brain, adding subtleties to the high. Some terpenes may affect the high because they lock into receptor sites in the brain and modify its chemical output. A few, such as thujone, one of the main terpenes in wormwood (which is used to make absinthe), bind weakly to the CB1 receptor. Others alter the permeability of cell membranes or the blood brain-barrier, allowing in either more or less THC. Others affect serotonin and dopamine chemistry by shutting off their production, affecting their movement, binding to their receptor sites, or slowing their natural destruction. Dopamine and serotonin, two of the main regulators of mood and attitude, are affected by some terpenes, as well as THC.

  By temporarily altering brain function, terpenes can affect mood, sensitivity, and perceptions, including balance and pain. When terpenes are mixed, as they are in natural plant oils, they each play a role in affecting brain function. Some combinations may work synergistically and others antagonistically, but each “recipe” of terpenes affects moods and feelings in its own way.

  Over 100 terpenes have been identified in marijuana. There are actually many more when one considers the multiple variations of each terpene. For instance, the characteristic citrus odor found in fruit rinds differs by type and even variety of fruit—oranges and lemons have different odors, and their terpenes, called limonenes, are mirror versions of each other. This is due to slight differences in the amounts of limonene, as well as other compounds that contribute to citrus elements.

  About 10-30% of marijuana smoke resin is composed of assorted terpenes. Some terpenes appear only occasionally in marijuana, while others are found all the time. The percentage of particular terpenes and the ratios in which they are found vary by plant variety. You experience this yourself when you notice different varieties have specific smells, indicating their individual essential oil makeup. Interestingly, hops and both groups of cannabis (low-THC hemp and high-potency marijuana)—contain similar complements of terpenes. One researcher found that the oil of common black pepper (piper nigrum) also has a group of terpenes similar to cannabis. Terpenes are produced in the trichomes, the same glands where THC is produced.

  Age, maturation, and the time of day can affect the amount, and perhaps ratios, of terpenes. One reason is their high evaporation rates at temperatures as low as 75° F (24° C). As plants mature, their odor gets more intense and sometimes changes as they ripen. Plants are constantly producing terpenes, but they evaporate under pressure from sunlight and rising temperatures. That means plants have more terpenes at the end of the dark period than after a full day of light. You can test this yourself—check a plant’s odor early in the morning and at the end of a sunny day. You will find more pungency earlier in the morning.

  Climate and weather also affect terpene and flavonoid production. The same variety of marijuana can produce different quantities and perhaps even different types of oils, depending on the type of soil in which it is grown or the fertilizers used. The terpenes described below are those generally most abundant in marijuana, though individual plants may differ widely both in total percentages of terpenes and in their ratios.

  Hops and Lemongrass

  MYRCENE is the most prevalent terpene found in most varieties of marijuana but not found in hemp. It is also present in high amounts in hops, lemon grass, West Indian bay tree (used to make bay rum), verbena and the plant from which it derive
s its name, mercia. Myrcene also appears in small amounts in the essential oils of many other plants. Its odor is variously described as clove-like, earthy, nutty, green-vegetative, and citrus. The various odors are the result of slight differences in the overall essential-oil makeup. All of these flavors and odors are commonly used to describe cannabis.

  Mango

  Myrcene is a potent analgesic, anti-inflammatory and antibiotic. It blocks the actions of cytochrome, aflatoxin B and other pro-mutagens that are implicated in carcinogenesis. It is also present in small amounts in many essential oils associated with anti-depressive and uplifting effects. Myrcene and THC are likely synergists, meaning a combination of the two molecules create a stronger experience than either one alone. Myrcene may affect the permeability of the cell membrane, allowing more THC to reach brain cells.

  Slightly overripe mangos contain large quantities of myrcene. Eating a mango 20-30 minutes before using marijuana gives the myrcene time to enter the bloodstream and start crossing the blood-brain barrier. Myrcene may help THC cross the barrier by opening the pathway or less likely, it might carry the molecule with it. The combination of THC and myrcene creates a stronger high, faster.

  LIMONENE is found in the rind of citrus and many other fruits and flowers. Limonene is the second, third or fourth most prevalent terpene in cannabis resins, depending on the variety. Everyone is familiar with the odor of citrus resins—they explode into the air when a fruit is peeled. The exact odor is determined by the structure of the terpene. Plants use limonene to repulse predators. For instance, flies have a group of receptors wired directly to the fly brain that are similar in function to the taste buds on our tongues. One of them detects noxious chemicals and responds to limonene as a toxin.