Cannabis cultivation is the cultivation of the Cannabis Sativa plant. Subspecies are C. sativa subsp. sativa and C. sativa subsp. indica. Wild or escaped Cannabis, previously classified as Cannabis ruderalis, is now regarded as the variety C. sativa subsp sativa var. spontanea. Various hybrids are cultivated. Cannabis is grown for a variety of purposes, including as a source of materials for use in various products, such as food, clothing, cosmetics and fuel and for the production of cannabis drug materials. Cultivation techniques for other purposes are very different: see Hemp.
The legal status of cannabis has led growers to implement novel cultivation methods for indoor growing, in order to avoid aerial surveillance of outdoor plots. These methods include: using a water or air-based growth medium (known as hydroponics and aeroponics respectively); the use of homemade, organic composted fertilizers; training and trellising techniques such as Screen of Green (also known as SCROG), Sea of Green (also known as SOG); and entire systems and methods such as the NIMBY no-dump method, Hempy Bucket, and the Krusty Freedom Bucket methods. Research into the production of cannabis for the drug Marinol and other more profitable and marketable forms of cannabis based medicines has further pushed the envelope of cannabis cultivation in all forms of laboratory, both public and private.
The emphasis on advanced cultivation techniques, as well as the availability of hybrid strains (with names like Northern Lights, Master Kush, NYC Diesel), is believed to be a factor in the increase in the overall quality and variety of commercially-available cannabis over the past few decades. However, well-grown heirloom strains (e.g. Thai, Colombian Gold, Panama Red) are still in use. The following covers the plant's entire growth, from germination to harvest.
The leaves are palmately compound, with serrate leaflets. During vegetative phase of growth, there is one leaflet on the first true leaf, three leaflets on the second, five on the third, and so on, up to about seven for C. sativa subsp. indica, and eleven for C. sativa subsp. sativa. The phyllotaxy reverses during reproductive phase, with bud leaves initially containing seven to eleven leaflets, and progressing down to one leaflet, and ultimately none at the terminal bud. Leaf arrangement is opposite during vegetative phase, and alternate during reproductive phase.
Cannabis plants are known for their production of oils, fibers, and compounds known as cannabinoids, including psychoactive tetrahydrocannabinol (THC) and non-psychoactive cannabidiol (CBD). Cannabis plants can be categorized on the basis of drug potential by the overall amount of cannabinoids produced, as well as by the relative ratio of THC to CBD. Overall cannabinoid production is influenced by environmental factors, but THC/CBD ratios are genetically determined and remain fixed throughout the life of the plant. This system of categorization recognizes three distinct categories. Non-drug (or low-intoxicant) types produce low levels of THC and CBD in both male and female plants. Drug types produce high amounts of THC but relatively low levels of CBD in both male and female plants. Intermediate types produce moderate amounts of THC, and produce CBD in comparable amounts; male plants of this intermediate type do not produce sufficient amounts of THC to be useful for drug purposes, while female plants may produce enough THC to be useful for drug production.
The genus Cannabis comprises a single species: Cannabis sativa. Two subspecies are recognized: C. sativa subsp. sativa and C. sativa subsp. indica; however, this classification is not universally accepted. Wild or escaped Cannabis was previously classified as a distinct species Cannabis ruderalis, but is now regarded as a variety, C. sativa subsp. sativa var. spontanea.
Generally only non-drug cultivars of C. sativa subsp. sativa are grown for industrial/agricultural purposes. For recreational or medicinal purposes, high-cannabinoid cultivars of both C. sativa subsp. sativa and C. sativa subsp. indica are grown, as well as hybrids of the two subspecies, and even a few hybrids that allegedly contain some C. sativa subsp. sativa var spontanea genetics.
Cultivation of the plant typically focuses on production of one of its above-noted ingredients. It is possible to grow the plants in a very close matrix, whereupon the resultant plants will have very fine fibers, which can be used to make fine cloth resembling silk. Alternatively, plants with select genetics, which are grown under close nutrient supervision and adequate lighting will produce higher quantities of THC.
While it is possible to grow cannabis simply for the purpose of a houseplant or as a hobby, the practice is quite challenging due to the need to keep the annual plant in a near perpetual vegetative state, which requires root pruning and artificial lighting for the winter months.
Cultivating Cannabis indoors traditionally has to do with growing the plants in a soil-like medium and adding fertilizer when the plants are given water. Cultivating marijuana indoors is more complicated and expensive than growing outdoors, but it allows the cultivator complete control over the growing environment. Cannabis grown outdoors can be just as potent as its indoor counterpart if tended to properly.
Plant characteristics which are generally selected for include:
When a cultivator has decided which plant or plants exhibit the most desirable traits, a cutting is taken and grown to maturity but never allowed to flower. This plant is referred to as a mother, and can be kept for a number of years, producing thousands of clones genetically identical to the mother.
While environmental stresses have been used to create pollen bearing male flowers on female plants- known as 'hermaphroditing' or 'hermying', this method is not preferred when creating feminized seeds; due to those plants most likely to revert to seed making being the ones which hermie soonest; hence passing on the genetic trait of instability of gender - desirable in the wild but not in cultivation.
Spraying selected leaves, branches and in cases where large amount of seed desired whole plants with colloidal silver solution has become a preferred method since the colloidal silver suppresses ethylene production in bud sites, stimulating male characteristics. Gibberellic acid has been used frequently; but is harder to find than colloidal silver, which involves nothing more than a small wall d.c. power supply and two pieces of solid silver jeweler's wire, or 99.999% silver coin. A method used by organic growers and promulgated by the famous Cannabis breeder Soma, is called 'Rodelization', or letting unpollenated female plants live several weeks longer than the normal harvest time. In such plants a hermaphroditic trait will self express in effort to continue the genetic line; the fact this method utilizes auto hermaphroditic traits which could contribute to instability in a plant's genetics is offset by grower observations that the tendency to auto-switch sex is not great in plants grown from seeds made this way, and the fact that it occurs naturally without effort on the part of the cultivator.
Caution should be exercised, as one does not always attain a beneficial cross with hybridizing.
First and foremost all substances coming into contact with the internal tissues of the plant should be sterilized to prevent infection. Cutting tools can be sterilized using bleach and growth media using an oven (most come sterilized).
Cuttings are taken ideally with a 90 degree cut on the branch to minimize surface area which is susceptible to infection. Then the large fan leaves near the bottom of the cutting are removed to minimize transpiration and the larger remaining fan leaf blades are cut to remove half of their surface area.
The stem is then re-cut at a 45 degree angle, ideally just below a growth node (the place on a stem where the leaves or branches are attached). Many growers claim cloning is most successful when clones are cut so that 1–2 growth nodes are surrounded by the growing medium, with 2–3 showing above the medium. Clones between 3 and 6 inches tall are considered ideal.
Many growers believe that the second cut (of 45 degrees) should be done underwater to prevent air bubbles (called embolisms) from forming in the xylem of the stem which may affect water and nutrient uptake. An embolism is a common cause of internal infections in the plant which is almost always fatal. Using a clean knife minimizes infection risks, which can wipe out a number of clones quickly.
Rooting hormone gel or powder mixes are then applied to the cut to promote root growth and inhibit fungal infection. The cutting is then placed in a rooting medium which may be a soil mix or a soil-less medium. Typical soil-less media are Perlite, vermiculite, peat moss, sand, rock wool or Oasis foam. A good medium is one that drains well, holds moisture and air well also. Oxygen is important for healthy root growth.
The cuttings in their new medium should be kept at a constant temperature (around 78 F) and with high humidity. Elevated humidity levels can be achieved by use of a humidifier or a humidity dome. Elevated humidity levels slow the transpiration rate which is important because without a root system the water uptake is very slow; If the transpiration rate exceeds the uptake rate the cutting is losing water and will wilt and die.
Many growers use a humidity dome as they are very inexpensive, around $7, and are easy to use. Many others improvise domes with simple plastic baggies secured with rubber bands (even less expensive and equally easy to use). When using a humidity dome, the dome should be removed at least twice a day and the rooting clones should be fanned to prevent mold and to give them some air circulation. Alternatively, you can cut off the bottom of a clear 3-liter bottle and temporarily put it over a single plant. The cap can easily be removed a couple times a day to easily refreshen air.
The rooting medium should be kept moist and should never dry out.
During other stages of growth one is advised to allow the soil to dry out to allow the roots to get oxygen and to prevent root rot. Since cuttings do not have roots this is not of concern. What is of concern is that a cutting will dry out and die, which occurs very rapidly.
Light intensity should be very low during the rooting process. High light intensities will force the plant to focus on photosynthesis at the expense of rooting. Light intensity should be increased during the last week up to normal illumination levels.
Cuttings usually take 7–14 days to develop root systems. Drooping is common within the first week. Cuttings that have not regained rigidity after 7 days are weak and are culled by most growers. To speed the rooting process keep the cuttings at constant temperature. Allowing the parent plant to become mildly nitrogen deficient before the cutting is taken will also speed rooting.
If performed correctly, the cuttings should stay green during their rooting time, and condensation should appear on the plastic coverings for the cuttings, which indicates proper humidity. After 7 days, healthy cuttings will appear strong with leaves reaching upward. Yellowing leaf tips are a common indicator of successful rooting. Browning likely indicates too much sunlight, too little humidity, cutting rotting in sitting water, or unsanitary cloning conditions.
In recent years, stores selling hydroponic grow equipment began offering automated machines (i.e.: EZCloner, etc.) in which trimmed cuttings are placed and left alone for approximately two weeks. Anecdotal accounts from established growers indicate these automated machines have near 100% success rates. Unfortunately, the cost (more than $300 USD) is prohibitive for most people that grow at home for personal use.
1) Sterilize equipment
2) Remove cutting from mother plant with a 90 degree cut
3) Remove lower fan leaves and remove half of the surface area of remaining fan leaves
4) Re-cut the stem (preferably underwater) with a 45 degree cut
5) Apply rooting hormone to cut end
6) Place cutting into a moist rooting medium
8) Open dome lid and fan cuttings twice a day and keep medium moist
9) Keep illumination level low and increase it from day 7–14
As cannabis and its cultivation are illegal in most parts of the world, considerable resources and effort are committed to both interdiction and counter-interdiction of cultivation. Thermal imaging helicopters, to detect heat lamps, and analysis of energy bills, to detect energy usage patterns of marijuana growers, have been used in prosecutions. In the US, thermal imaging cameras are considered to violate civil liberties embedded in the United States Constitution. This has resulted in significant changes to growing trends and availability.