Cannabis cultivation


This article presents common techniques and facts regarding the cultivation of cannabis, primarily for the production and consumption of its infructescences. Cultivation techniques for other purposes differ.

Botany

Cannabis belongs to the genus Cannabis in the family Cannabaceae may include three species, Cannabis, Cannabis sativa, and Cannabis ruderalis, or one variable species. It is typically a dioecious annual plant.
C. sativa and C. rudealis generally grow tall, with some varieties reaching 4 metres, or 13 feet. Female plants produce tetrahydrocannabinol as the season changes from summer to autumn. C. ruderalis is very short, produces only trace amounts of THC, but is very rich in cannabidiol, which may be 40% of the cannabinoids in a plant and is an antagonist to THC, and it flowers independently of the photoperiod and according to age. However, commercial cross-bred hybrids containing both ruderalis, indica and/or sativa genes exist.

Cultivation requirements

Cannabis needs certain conditions to flourish.

Growth medium

Soil is required, except for cannabis grown with hydroponics or aeroponics
Overall growing is the best as choice as full control is enabled

Warmth

The optimal day temperature range for cannabis is. Temperatures above 31 °C and below 15.5 °C seem to decrease THC potency and slow growth. At 13 °C the plant undergoes a mild shock, though some strains withstand frost temporarily.

Light

Light can be natural or artificial.
Under artificial light, the plant typically remains under a regime of 16–24 hours of light and 0–8 hours of darkness from the germination until flowering, with longer light periods being conducive to vegetative growth, and longer dark periods being conducive to flowering. However, generally cannabis only requires thirteen hours of continuous light to remain in the vegetative stage. The 'Gas Lantern Routine' is an alternate lighting schedule that has proven to be successful for growing cannabis, while saving a significant amount of energy. For optimal health, cannabis plants require a period of light and a period of dark. It has been suggested that, when subjected to a regimen of constant light without a dark period, cannabis begins to show signs of decreased photosynthetic response, lack of vigor, and an overall decrease in vascular development. Typically, flowering is induced by providing at least 12 hours per day of complete darkness. Flowering in cannabis is triggered by a hormonal reaction within the plant that is initiated by an increase in length of its dark cycle, i.e. the plant needs sufficient prolonged darkness for bract/bracteole to begin. Some Indica varieties require as little as 8 hours of dark to begin flowering, whereas some Sativa varieties require up to 13 hours.

Water

Watering frequency and amount is determined by many factors, including temperature and light, the age, size and stage of growth of the plant and the medium's ability to retain water. A conspicuous sign of water problems is the wilting of leaves. Giving too much water can kill cannabis plants if the growing medium gets over-saturated. This is mainly due to oxygen not being able to enter the root system. Anaerobic bacteria start to accumulate due to waterlogged, stale conditions. They begin to consume plant roots, beneficial bacteria, as well as nutrients and fertilizer. When using soil as a growth medium, the soil should be allowed to dry adequately before re-watering.

Humidity

Humidity is an important part of plant growth. Dry conditions slow the rate of photosynthesis. Ideal levels of humidity for optimal growth are 40%RH-60%RH.

Nutrients

Nutrients are taken up from the soil by roots. Nutrient soil amendments are added when the soil nutrients are depleted. Fertilizers can be chemical or organic, liquid or powder, and usually contain a mixture of ingredients. Commercial fertilizers indicate the levels of NPK. In general, cannabis needs more N than P and K during all life phases. The presence of secondary nutrients is recommended. Micronutrients rarely manifest as deficiencies.
Because cannabis' nutrient needs vary widely depending on the variety, they are usually determined by trial and error and fertilizers are applied sparingly to avoid burning the plant.

Stages of development

Germination

Germination is the process in which the seeds sprout and the root emerges. In cannabis, it takes from 12 hours to 8 days. Warmth, darkness, and moisture initiate metabolic processes such as the activation of hormones that trigger the expansion of the embryo within the seed. Then the seed coat cracks open and a small embryonic root emerges and begins growing downward, if placed in a proper growing medium. Soon the root is anchored and two circular embryonic leaves emerge in search of light and the remains of the seed shell are pushed away. This marks the beginning of the seedling stage.
Germination is initiated by soaking seeds either between wet paper towels, in a cup of water at room temperature, in wet peat pellets, or directly in potting soil. Peat pellets are often used as a germinating medium because the saturated pellets with their seedlings can be planted directly into the intended growing medium with a minimum of shock to the plant.

Seedling phase

The seedling stage begins when the seed coat splits open and exposes the root and round “seed leaves” or cotyledons. It lasts from 1 to 4 weeks and is the period of greatest vulnerability in the life cycle of the plant, requiring moderate humidity levels, medium to high light intensity, and adequate but not excessive soil moisture.
Most indoor growers use compact fluorescent or T5 fluorescent lights during this stage as they produce little heat. HPS and MH lights produce large amounts of radiant heat and increase the rate of transpiration in the plant which can quickly dry out seedlings with their small root systems.

Vegetative phase

Duration: 1–2 months indoors. In this stage the plant needs a significant amount of light and nutrients, depending on the genetics of the particular plant. It continues to grow vertically and produce new leaves. The sex is starting to reveal itself, which is a sign that the next stage begins. Concurrently the root system expands downwards in search of more water and food.
When the plant possesses seven sets of true leaves and the 8th is barely visible in the center of the growth tip, or shoot apical meristem, the plant has entered the vegetative phase of growth. During the vegetative phase, the plant directs its energy resources primarily to the growth of leaves, stems, and roots. A strong root system is required for strong floral development. A plant needs 1 or 2 months to mature before blooming. The plant is ready when it has revealed its sex. Plant size is a good indicator of sex. Females tend to be shorter and branchier due to their raceme type inflorescence than males, whose flowers grow in panicles. The males are then usually culled when they are identified, so that the females will not be pollinated, thus producing parthenocarpic fruits.
During the vegetative phase, cultivators generally employ an 18- to 24-hour photoperiod because the plants grow more quickly if they receive more light, although a warmer and cooler period are required for optimal health. Although no dark period is required, there is debate among cultivators as to whether a dark period is beneficial, and many continue to employ a dark period. Energy savings often support using a dark period, as plants undergo late day decline and therefore lighting during the late night hours is less effective.
The amount of time to grow a cannabis plant indoors in the vegetative stage depends on the size of the flower, the light used, the size of the space, and how many plants are intended to flower at once, and how big the strain gets in "the stretch".
Cannabis cultivators employ fertilizers high in nitrogen and potassium during the vegetative stage, as well as a complete micro nutrient fertilizer. The strength of the fertilizer is gradually increased as the plants grow and become more hardy.
Advanced cultivation methods include:
  1. training and trellising techniques such as Screen of Green, Sea of Green "Super cropping" and LST super cropping; 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.
  2. using a water or air-based growth medium
  3. the use of homemade, organic composted fertilizers
The emphasis on advanced cultivation techniques, as well as the availability of hybrid strains, is believed to be a factor in the increase in the overall quality and variety of commercially available cannabis over the past few decades. The Internet in particular has brought together widely diverse genetics from around the world through trading and purchasing. However, well-grown heirloom strains are used to produce 1 gram per watt harvest.

Pre-flowering phase

Also called the stretch, this takes one day to two weeks. Most plants spend 10–14 days in this period after switching the light cycle to 12 hours of darkness. Plant development increases dramatically, with the plant doubling or more in size. Production of more branches and nodes occurs during this stage, as the structure for flowering grows. The plant starts to develop bracts/bracteoles where the branches meet the stem. Pre-flowering indicates the plant is ready to flower.

Flowering and fruition phases

The flowering phase varies from about 6 to 22 weeks for pure indicas with their shorter flowering time than pure sativas. Mixed indica/sativa strains have an intermediate flowering time. The sex is clearly revealed in the first phase, the actual flowering. Males produce little ball-like flowers clustered together like grapes called panicles. Most plants begin to flower under diminishing light. In nature, cannabis plants sense the forthcoming winter as the Earth revolves about the Sun and daylight reduces in duration. The next phase consists in the fruition : the females inflorescences that were not pollinated start to produce infructescences that contain sticky white resin-containing glands in a final attempt for pollination by windborne male pollen. The trichomes produce resins that contain the largest amounts of THC and CBN, the two main psychoactive substances. Fertilized females continue to produce resinous trichomes but more plant energy is consumed by the production of seeds, which can be half the mass of a fertilized bract; thus, to maximize resin per gram, infertile cultivation is preferred.
Inflorescence that produce no seeds are called sin semilla. Potent sin semilla is especially important to medical users, to minimize the amount of cannabis they must consume to be afforded relief. Cannabis with seeds is generally considered to be of inferior quality and/or grown with inferior technique.
Cannabis grown is induced into flowering by decreasing its photoperiod to at least 10 hours of darkness per day. In order to initiate a flowering response, the number of hours of darkness must exceed a critical point. Generally the more hours of darkness each day, the shorter the overall flowering period but the lower the yield. Conversely, the fewer hours of darkness each day, the longer the overall flowering period and the higher the yield. Traditionally, most growers change their plants lighting cycle to 12 hours on and 12 hours off since this works as a happy medium to which most strains respond well. This change in photoperiod mimics the plant's natural outdoor cycle, with up to 18 hours of light per day in the summer and down to less than 12 hours of light in fall and winter. Some 'semi-autoflowering' strains that have been bred exclusively for outdoor use, particularly in outdoor climates such as that of the UK, will start flowering with as much as 16–17 hours of light per day. Usually they can start flowering in July and finish far earlier than other strains, particularly those that haven't been bred as outdoor strains. Semi-autoflowering strains can be harvested before the weather in northern latitudes becomes very wet and cold, whereas other strains are just finishing flowering, and may suffer from botrytis caused by wet weather. Alternatively growers may artificially induce the flowering period during the warmer months by blacking out the plants for 12 hours a day i.e. by covering the plants with black plastic for example, which excludes all light during this period so the plant can flower even during long days.
Although the flowering hormone in most plants is present during all phases of growth, it is inhibited by exposure to light. To induce flowering, the plant must be subject to at least 8 hours of darkness per day; this number is very strain-specific and most growers use 12 hours of darkness.
Flowers from certain plants are called bract/bracteole, and are the most prized part of the plant. During the late period, the bract/bracteole are easily visible to the naked eye. Bract/bracteole development begins approximately 1–2 weeks after the photoperiod is reduced. In the first weeks of flowering a plant usually doubles in size and can triple. Bract/bracteole development ends around 5 weeks into flowering and is followed by a period of bract/bracteole “swelling”. During this time the buds greatly increase in weight and size.

Outdoor cannabis cultivation

Cannabis can be grown outdoors, either on natural soil or in pots of pre-made or commercial soil. Some strains perform better than others in outdoor settings, an attribute that depends on different conditions, variables and aspects. Outdoor marijuana strains, like most other strains, can be bought in numerous locations and over a hundred different cannabis strains that are bred for outdoor growing exist—many of these outdoor cannabis seeds are simply copies of other pre-existent strains or seeds with different names and descriptions.
To generate optimum quantities of THC-containing resin, the plant needs a fertile soil and long hours of daylight. This means THC production for outdoor growth occurs optimally anywhere within 35° of the equator. Typical growing regions include Mexico, Nepal, Northern India, many parts of Africa, Afghanistan, the United States and Australia.
In most places of the subtropics, cannabis is germinated from late spring to early summer and harvested from late summer to early autumn.
burn on a leaf
Outdoor cultivation is common in both rural and urban areas. Outdoor cultivators tend to grow indica-based strains because of its heavy yields, quick maturing time, and short stature. Some growers prefer sativa because of its clear-headed high, better response to sunlight, and lower odor emissions. Growers cultivate on their own property or practice guerrilla farming i.e. to plant cannabis in remote areas such as forest clearings or mountain cliffs which they rarely visit. However, such a method is prone to theft – so much so that some ingenious growers even attach pots to trees to decrease this possibility. Guerrilla growing has given birth to the activist movement Operation Overgrow, where the plant is grown with the explicit purpose of introducing the cannabis plant into the natural ecosystem.
For outdoor cultivation, growers choose areas that receive twelve hours or more of sunlight a day. In the Northern Hemisphere, growers typically plant seeds in mid-April, late May, or early June to provide plants a full four to nine months of growth. Harvest is usually between mid-September and early October. In North America, northern locations are preferred, but southern locations are also known to be good producers.
Where local laws do not permit growing cannabis, cultivators sometimes grow in forests or rugged and rural areas where the local population is unlikely to find the crop. Cannabis is also grown hidden by a crop that is taller, such as maize. This is reported by the United States government to be common in the midwestern states. Bamboo and elderberry are also used as camouflage companion plants.
Some government agencies, including the Drug Enforcement Administration, have claimed that in State and National Parks people have been injured by cannabis farmers protecting their crops using booby traps; no arrests or convictions for this had been made.

Indoor cannabis cultivation

Cannabis can be grown indoors in a soil-like medium under artificial light, adding fertilizer when the plants are given water. Cultivating cannabis indoors is more complicated and expensive than growing outdoors, but it allows the cultivator complete control over the growing environment. Plants of any type can be grown faster indoors than out due to 24-hour light, additional atmospheric CO2, and controlled humidity which allows freer CO2 respiration.
Plants can also be grown indoors through the use of hydroponics.
To grow plants indoors, a growing medium, water, nutrients, light and air need to be supplied to the plant.

Supply of light

There are several different plant grow lights available. Currently the best source of light for cannabis remains to be metal halide or ceramic metal halide in the range of 3-4000k. Cannabis plants also require both dark and light photoperiods, so the lights need a timer to switch them on and off at set intervals. The optimum photoperiod depends on each plant.
Recent advancements in LED technology have allowed for diodes that emit enough energy for cannabis cultivation. These diodes can emit light in a specific nanometer range, allowing for total control over the spectrum of the light. LEDs are able to produce all of their light in the photosynthetically active range of the spectrum.
Reflectors are often used in the lamps to maximize light efficiency. At a medium growing density of 15 plants and 430 watts per square meter, electricity costs are not insignificant. Plants or lights are moved as close together as possible so that they receive equal lighting and that all light coming from the lamps falls upon the plants. Maximum efficiency can be obtained by creating a slightly concave canopy such that the periphery and centre of the canopy are both at the optimum distance from the light source. Often, the distance between lamp and plant is in the range of with high pressure sodium lamps, to with other lamps, such as compact, large and high-output fluorescent lamps. With proper cooling any light type can be moved extremely close to plants to combat the inverse square law, but there are reasons to keep some distance from the canopy regardless of heat concerns; excessive light can cause bleaching of the plant material and the total canopy area contacted by light is decreased as the source is moved closer. Maximum efficiency should be obtained by maximizing the average light intensity per square foot times the number of square feet of plant matter contacted. Some cannabis cultivators cover the walls of their grow-room with some type of reflective material, or alternatively, white paint to maximize efficiency.
One commonly used covering is PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing into the room to reflect light, and the black facing the wall, to reduce fungus and mold growth. Another common covering is flat white paint, with a high titanium dioxide content to maximize reflectivity. Some growers consider Mylar sheeting to be very effective when it lines grow room walls, along with Astrofoil, and Foylon.

Control of the atmosphere

When growing indoors, the cultivator should maintain as close to an ideal atmosphere inside the grow-room as possible. The air temperature should be maintained within a specific range, typically with deviations no larger than 10 °C with a cooler night and warmer day. Adequate levels of CO2 must be maintained for the plants to grow efficiently. It is also important to promote vigorous air circulation within the grow room, which is usually accomplished by mounting an extraction fan and one or more oscillating fans.
Assuming adequate light and nutrients are available to plants, the limiting factor in plant growth is the level of carbon dioxide. Ways of increasing carbon dioxide levels in the grow-room include: bottled carbon dioxide, carbon dioxide generators, a milk jug and yeast solution, a baking soda and vinegar mixture in a container, or dry ice.
Certain plants emit a distinctive odor during their reproductive phase. This presents difficulties to those who are cultivating in places where it is illegal, or for growers who may prefer discretion for other reasons. The most common way of eliminating odor is by pulling odorous air through a carbon filter. Many cultivators simply attach a large carbon filter to their air extraction system, thereby filtering any smell before the air is expelled from the grow-room. Another way of eliminating odor is by installing an ozone generator in the extraction ducting. The air is forced past the ozone generator by the extraction fan, and the odorous air is neutralized as it mixes with the ozone; however the cultivator must ensure that the air is thoroughly mixed before it is expelled outside, lest some odor escape. Care must be taken to prevent excessive ozone concentrations in the garden itself, or where it might be inhaled by the grower or their family. Ozone itself has a distinctive smell and is harmful to living things, although the molecule breaks down quickly in atmospheric conditions.
Indoors there are numerous configurations that people utilize to grow quality cannabis. Some growers will convert an entire room or closet, making it devoted to growing cannabis. A relatively new configuration involves the use of grow tents. These are plastic or metal framed tents which are covered in a strong flexible reflective plastic and have light proof zipper doors. Tents come in all sizes and many already have holes for exhaust fans/ducting as well as mounts for HID lamps.
Some growers will construct grow cabinets made out of an old refrigerator, cabinet, dresser drawer or similar.

Popularity and extent

Indoor growing has become increasingly common over the past decade because of the increased availability of equipment, seeds and instructions on how to cultivate. So-called grow-ops are seen by many marijuana enthusiasts as a much cheaper way to gain a steady, higher-quality supply of cannabis. On a larger scale they have proven a viable commercial venture, with some law enforcement agencies finding grow-ops large enough to yield several kilograms of cannabis. More expansive grow-ops are generally more susceptible to detection than smaller operations.
In the UK, so much cannabis is grown in illegal facilities that the UK is an exporter of cannabis. After cannabis as a drug was rescheduled as a Class B drug in 2008, more people started reporting on their suspicions of illegal operations and in 2009-2010 almost 7000 illegal facilities were found by police in one year. Vietnamese teenagers are trafficked to the United Kingdom and forced to work in these facilities. When police raid them, trafficked victims are typically sent to prison.
Because individual grow light power generally ranges from 250 watts to 1000 watts or more and because the lights remain lit for a long time each day, differences in utility bill costs are a significant security issue. Power companies inform law enforcement if they see a significant increase in power usage relative to a household's previous electricity costs or if power is being stolen by bypassing the meter. Employing energy saving methods is a common way to alleviate this, for instance; switching off light bulbs when leaving rooms, purchasing energy efficient appliances, using TVs or computers less, buying lower power light bulbs and so forth.
Some plants, can give off strong odors as they grow, resulting in detection of illegal growing operations. Growers frequently use carbon scrubbers and ventilation to control odors. This typically involves forcing air from the grow room through a device containing activated carbon, then venting it outdoors. Others use an ozone generator. Ozone reacts with odor molecules in the air, permanently eliminating them. However, ozone can build up to levels that may be hazardous both for grower and plant. As a last resort, keeping windows firmly shut and using strong air fresheners can control smells. Checking outside to see if any smells are emanating from indoors is often a necessary precaution, as many growers become acclimated to the smell, and fail to realize just how pervasive the odor may be. Many store plants in more isolated areas such as a basement or attic to prevent smell detection. Another less common solution is to simply grow a strain with a weaker odor.
Storing plants and lights away from windows and areas that visitor may see is also common, as is keeping the plants in an attic or basement. Some growers, finding this impractical, may cover windows with light-resistant materials. This can solve the problem of escaping bright light but may arouse suspicion amongst neighbors and local residents.
Many cultivators face the risk of fire. Fires normally originate from faulty electrical equipment or wiring. Shoddy fixtures and sockets, improperly grounded equipment, and overloaded circuit breakers are some of the most prevalent causes. Because of the large amount of electricity needed for large-scale cultivation, old or damaged wiring is prone to melt and short. Some commercial growers steal power to hide electricity use, and many do not ensure that their wiring is safe. Many growers adapt light cycles so that the lights are on when they are home and off when they are away.
Another fire hazard is plants making contact with hot HID bulbs. Growers using fluorescent bulbs with reasonable air circulation do not have this problem. Word of mouth can be as much a threat to growers as any of the above issues. Often, a few sentences of conversation overheard can result in a tip-off and thus speedy detection. It is for this reason that many growers are reluctant to talk about their cultivation.

Housing damage

For houses used as grow-ops, the interiors may have received significant structural, electrical and heating system modifications not in accordance with applicable building, natural gas and electrical codes, such as overloaded existing electrical system or a bypass circuit to avoid paying for the electricity required to power the high intensity light bulbs and fans, disconnected furnace venting, or holes in floors and walls for increased airflow. These changes replicate warm, humid climates where hybrid plants flourish and produce high potency cannabis. Such modifications may result in considerable structural damage. Cultivation over a period of time may lead to moisture and toxic mold.
One of the largest such examples was masterminded by a Markham, Ontario real estate agent, John Trac, who turned 54 rented houses into grow-ops; he was convicted and imprisoned.
Contractor and television presenter Mike Holmes said that while houses formerly used for growing cannabis could be bought very cheaply from banks or other owners, repairs and remediation could cost around $100,000 CAD, which may exceed price savings. Holmes noted that in one of his past jobs on Holmes on Homes, he and his crew gutted the entire house after discovering it was a grow-op.
In some municipalities, after the police raid a grow-op house they are required to contact the municipality to ensure that it is put back in good condition before being offered for sale, while real estate agents and sellers may be required by law to disclose that the home had been a grow-op. Home inspectors routinely fail to detect tell-tale signs that a house had been used as a grow-op.

Harvesting, drying and curing

There may be different goals when harvesting a plant:
A typical indicator that a plant is ready to be harvested for smoking, is when most trichomes have turned cloudy and 5% to 15% of the trichomes have turned a reddish brown/amber.
In general, harvesting consists of drying and curing. Curing is an oxidization and polymerization process which takes place in sealed containers of cannabis, over time.
Ripeness is defined as the point where THC and other cannabinoid production has reached maximum levels, but before cannabinoids have begun to degrade/breakdown. This is seen under a 30x-60x microscope by examining the trichomes on the flowers. When trichomes are undeveloped they are completely clear. They turn white/cloudy which is when trichomes have max levels of cannabinoids. Eventually trichomes start turning amber/purple/red, which is when cannabinoid content has started to degrade. Harvesting before most trichomes have turned white may reduce the overall potency and efficacy time. Harvesting too late produces more of a sleepiness effect as the THC degrades to CBN.
Some growers use a brix to measure "sugar" content.

Drying

The plants are dried at room temperature in a dark space. It is actually optimal to keep the temperature between because many terpenoids evaporate at temperatures beyond. This process can take from a few days to two weeks, depending on the size and density of the buds and the relative humidity of the air. Humidity should be kept between 45% and 55% humidity. Higher humidity will create a mold and mildew risk, while lower humidity will cause the material to dry too quickly. If the plant material dries too quickly, some of the chlorophyll will fail to be converted to a different chemical form which will result in a sub-optimal taste and a harsher smoke when combusted and inhaled. Stable temperature preserves cannabinoids well. Some believe flowers should be hung by their stalks, allowing the internal fluids of the plant to remain in the flowers. Others believe the cut stem is simply a handy non-sticky place from which to hang the plant. Roots are removed, and when the stems in the middle of the largest buds can be snapped easily, the plant is considered dry enough to be cured. Drying is done in a dark place, as THC resins deteriorate if exposed to light and the degradation product CBN forms, significantly altering the cannabinoid profile of the dried flowers.
Drying the harvest is generally not considered risky by novice indoor growers of cannabis who would like to assume that they have gotten safely to the end of their "grow" by the time they are harvesting their plants. However, generally speaking most will underestimate the sheer scale of odor produced during the cropping, moving and hanging plants to dry. Indoor growers in areas where cultivation is illegal may consider this an obstacle in their overall efforts as the first three days of drying produces very large amounts of discernible odor which the grower themself may be desensitised to. These will be evaporating and likely discernible to others anywhere in the vicinity of the general area. In populated areas consideration of containment & concentration of odor molecules may be employed to reduce risk. In less populated areas with good air movement dissolution and dispersal techniques for odor management may be employed i.e. ventilation from high points such as a chimney or roof vents. Whatever method is to be employed, novice growers in illegal areas would do well to not underestimate the sheer volume of organic molecules being dissipated into the air when harvesting.
Cannabis is fully dry for "curing" when the moisture level reaches 55%-65% RH. A simple way to check this is by closing the cannabis up in an airtight glass container with a hygrometer. The container is stored for 12 hours at 22 °C and the hygrometer checked. 65% and above readings mean the jar needs to be opened for a few hours and then closed up, to allow more moisture to escape. The jar is again checked after 12 hours and the process repeated until a steady 55% is reached.

Curing

Once cannabis is dried to 62%, it is sealed in airtight jars to 'cure.' The minimum time for a cure is 30 days. Some growers even cure as long as six months, while others do not cure at all. As with tobacco, curing can make the cannabis more pleasant to smoke. For the same reasons as when drying, curing jars are stored in a cool, dark place.

Brick weed

Brick weed is a curing and packaging method of cannabis cultivation that consists in drying the bud for a short period, if at all, and pressing it with a hydraulic press, compacting the whole plant into a brick, hence the name brick weed. This method is mainly used in the top cannabis producing countries like Mexico and Paraguay where it is largely exported. Brick weed has a low THC level and less potent aroma and taste.

Pest Management

Both indoor and outdoor growers are likely to confront issues regarding pests. Indoor growers have problems with pests, they can be brought in by hitchhiking on humans or through open exposure to the outdoors. The most common insect pest found on above ground plant parts, leaves, flowers and stems, include aphids, thrips, mites and loopers. Below ground pests that feed on the roots can also be present and include fungus gnats and root aphids. Root aphids, namely the rice root aphid can be particularly problematic due to its high reproductive rate and discrete habitat.
Several plant diseases may also be prevalent and including bud rot, powdery mildew and root rot.
If any of these pests are caught too late, eradication of many destructive species may prove futile unless all infected plants are removed from the space and sterilization methods employed.

Organic and inorganic pest controls

In any case, experienced growers recommend caution when using chemical pesticides, for they may have toxic effects on the environment, the plants themselves and in turn cannabis consumers. As a general rule, experts mandate the deployment of pesticides clearly marked as "safe to use on food crops." However, the EPA has not registered any pesticides for use on cannabis, making the use of any pesticide on cannabis federally illegal.
Substances that have been used and considered to induce little or no harm include:
Substances used on cannabis but unknown if harm could occur:
The modification of a plant's growth habit is called training. Indoor cultivators employ many training techniques to encourage shorter plants and denser canopy growth. For example, unless the crop is too large to be extensively pruned, cultivators remove adventitious growth shoots, often called suckers, that are near the bottom of the plant and/or receive little light and will produce poor quality buds. Some cultivators employ plant training techniques to increase yields indoors:

Topping

Topping is the removal of the top of the apical meristem, called the apex or terminal bud, to transfer apical dominance to the shoots emanating from the two nodes immediately beneath the pruning cut. This process can be repeated on one or both of the two new meristems, when they become apically dominant, with the same results. This process can actually be repeated nigh infinitely, but over-diffusion of apical dominance produces smaller, lower quality buds, so it is usually done no more than a few times. Topping also causes more rapid growth of all of the branches below the cut while the plant heals.

Pinching

Pinching is similar to topping in that it causes lower branches to grow more rapidly, but the apical meristem maintain apical dominance, which is especially useful if the plant has already been topped. Pinching is performed by firmly pinching the apical meristem so as to substantially damage vascular and structural cells but without totally breaking the stem. This causes lower limbs to grow more rapidly while the pinched tissue heals, after which time the stem resumes apical dominance.

LST'ing

LST stands for Low Stress Training and is another form of supercropping, many times referred to as LST super-cropping. This technique involves bending and tying the plants branches to manipulate the plant into a more preferred growth shape. This method of training works very well for indoor growers who need to illuminate their plants using overhead lights. Since light intensity greatly diminishes with increased distance, LST'ing can be used to keep all growth tips at the same distance from the light and can achieve optimal light exposure. LST can be used in conjunction with topping, since topping increases axial growth. Topping is often done a few weeks before beginning LST'ing. The training works by changing the distribution of hormones—more specifically auxins—in the plant. LST'ing resembles the training of grape vines into their support lattices. Outdoor gardeners also employ training techniques to keep their plants from becoming too vertical.

SOG

In contrast to the "Screen of Green" method, Sea of Green growing depends on the high density of plants to create uniformity in the crop. In this technique, which is often grown in hydroponic media, only the colas of the plants are harvested. Containers are used to enforce the geometric distribution of flowers and plant material, as well as their exposure to lighting and atmosphere. Sea of green is popular with commercial cultivators, as it minimizes the amount of time a plant spends in vegetative stage, and allows very efficient light distribution, keeping the plants much closer to the lights than when grown to full size.

SCROG

SCROG, short for SCReen Of Green, is an advanced training technique for cultivating cannabis, mainly indoors. Closely resembles SOG with the difference being that SCROG uses extensive training to produce the same field of bud effect with only one plant. Medical growers may find this a helpful technique to maximize harvest if they are only allowed a certain number of plants. A screen such as chicken wire is hung over plants so that the tips of branches are kept at the same level. This allows even light distribution to all of the nodes/bud sites. Once the flowering stage begins, the flower tips reach through the wire and are at relatively equal distances from the light source.
Vegetative state:
The plant should remain in the vegetative state until 70 to 80 percent of the net is full. As a branch reaches 7.5 to 10 centimetres above the wire it is pulled back under the wire and so trained to grow horizontally until flowering. Because of the amount of plant required to fill the net, the vegetative period may require longer than normal to be ready for flowering.
Timing:
Timing is vital to the success of a SCROG grow. If the net is not full at harvest, valuable space has been wasted. If the net is too full then the buds will be too crowded to develop properly. Knowing how a plant grows can help to visualize when to flower for maximum effect.

Hydroponics

Hydroponic cultivation generally occurs in greenhouses or indoors, although there is no practical obstacle to growing outdoors. In general, it consists of a non-soil medium exposed to a nutrient and water flow.
There are many types of hydroponic systems. If the nutrient solution floods the loose growing medium and recedes for aeration, this is an ebb and flow or flood and drain system. Systems that gradually drip solution onto the medium are drip systems. Systems that intermittently spray roots floating in air are called aeroponic systems. If aerated water runs down a channel lined with a film of rooting medium, this is a nutrient film technique system. A series of tubes intermittently running high flow nutrient solution into the tops of growing containers use a top feed system. Aquaponics, another growing method that is gaining popularity, employs the use of fish water and recirculates that water from the fish holding tank to the growing bed.
Hydroponic systems greatly increase aeration of plant roots, and increase control of nutrient uptake. Hydroponic systems are decidedly more difficult to operate for the amateur or hobby grower, as over-fertilization is common, because there is no soil to act as a nutrient buffer. For this reason, many growers now use coconut fiber as a soil-less medium because of its high drainage and buffering capabilities that make it almost impossible to over-fertilize. Additionally, if a hydroponic system fails, the crop has a high probability of dying as the roots rapidly dry out.
There is now a new breed of hydroponic configurations such as the Omega Garden, the B-Pod and the EcoSystem Vertical Growing System that use circular designs to maximize efficiency. This consists of plants being placed or, in the case of the Omega Garden, revolving around a central light that makes maximum use of the light output.

Genetics

Selection of mother plants

An important factor while cultivating photoperiod independent cannabis is selecting the best genetics for one's crop. This is frequently done by selecting one or more known strains, or strains with preferred genetics, and then growing a number plants to find which exhibit the characteristics most desirable. These genetics should typically yield at least 1 gram per watt per month of flower.
Plant characteristics generally selected for include:
strains, also known as day-neutral cannabis are a relatively new development for the home cultivator. These autoflower strains are usually crosses that contain high percentages of well known photoperiod strains and Cannabis ruderalis with its autoflowering characteristics. The plant produced from an autoflowering seeds will transition from a very short vegetative period, usually 2 to 3 weeks from germination, into flowering regardless of photoperiod. The result is that no separate vegetative and flowering lighting environment are needed. Flowering is dependent on the plants age not the time of year or ratio of light to dark hours. Autoflowers will finish from seed in 12/12, 18/6, 20/4 or even 24/0 lighting.
The first autoflowering cannabis seed on the market was the Lowryder #1. This was a hybrid between a cannabis ruderalis called William's Wonder and a Northern Lights #2. The genetics of the ruderalis was still highly present which made for a very low yield and little psychoactive effect.
After many years of autoflower inbreeding seed makers have now come up with autoflowering strains that can produce yields close to the regular strains and still are flowering independent from the light cycle. The first autoflowering strains came from breeder STICH but now almost all major seed companies have their strains of super autoflowers that can grow up to 2 meters and produce yields up to 900 g/m2 of growth.

Feminized seeds

Instability of gender is a desirable trait in the wild, where reproduction is the most urgent goal. In cultivation, gender predictability is more helpful, because female plants that have not been pollinated are the most productive of the psychotropic material. It is possible to use a combination of cloning and "shocking" of plants to get them to produce feminized seeds that reliably produce female offspring. A clone retains the same sex throughout its life, so the clone of a female plant is also female.
Environmental stresses sometimes create pollen bearing male flowers on female plants—known as hermaphroditism or 'hermying'.
A method used by organic growers and promulgated by the cannabis breeder Soma, is called 'Rodelization', or letting un-pollinated female plants live several weeks longer than the normal harvest time. In such plants a hermaphroditic trait self-expresses in an effort to continue the genetic line.
Some vendors of feminized seeds assert that hermaphroditic "parents" do not create reliable feminized seeds, since the offspring may retain the tendency of hermaphrodytism. Others believe that this method utilizing auto-hermaphroditic traits is offset by grower observations that the tendency to auto-switch sex is no greater in plants grown from seeds made this way, than occurs naturally.
Colloidal silver suppresses ethylene production in bud sites, stimulating male characteristics. Spraying selected leaves, branches and – in cases where a large amount of seed is desired – whole plants with colloidal silver solution has become a preferred method of obtaining feminized seeds. Most plants treated with CS will turn intersex within 2 weeks of triweekly treatment, producing viable pollen within 4. Gibberellic acid has also been used for the same purpose, but it is harder to acquire than colloidal silver and can be difficult to dissolve into solution. One method of obtaining colloidal silver utilizes a small direct current power supply and two pieces of solid silver jeweler's wire, or silver coin.
Some cultivators claim that the genes responsible for hermaphroditism are present and may be expressed under stress from any of the above methods and that once expressed, this characteristic passes to seeds regardless of what activated it. This view, in large part, is incorrect, as a random half of the genes present in each of the parental plants passes to the next generation, regardless of whether the genes that contribute to hermaphroditism were induced by stressors or not. This widely accepted Mendelian model of inheritance does allow for genetic mutations that have occurred in the germline of an organism to be passed on to any offspring, but this process applies to all DNA sequences, not just those contributing to hermaphroditism. The inheritance of acquired characteristics that are not directly coded in the DNA sequence has recently received much attention in the area of genetic research and could possibly explain any anecdotal evidence for increased hermaphroditism in the offspring of plants induced to a hermaphroditic state. However, a more likely explanation is that by propagating plants easily induced to hermaphroditism by environmental stressors, the frequency of genetic elements contributing to this trait is increased by artificial selection following traditional genetic models of inheritance. Some theories suggest it is possible to selectively breed hermaphroditic cannabis to express the female flowering before the male flowering occurs, though this kind of selective breeding is beyond the capabilities of most cultivators.

Hybrid vigor

When crossing two strains of cannabis, the resultant hybrid may possess what is called hybrid vigor. In general, this produces a plant that is healthier, stronger, or quicker growing than its predecessors. Sometimes, in the case of a plant that has been brought back from fruiting, it may be beneficial to cross it back with another relative, in the hopes that it becomes invigorated.
Caution should be exercised, as one does not always attain a beneficial cross with hybridizing.

Vegetative propagation (cloning)

Like most plants, cannabis has the potential for vegetative propagation, with the most common and simple method being cutting. Cutting is characterized as a cloning method, since the derived plants have identical DNA to the "mother plants".
Under appropriate environmental conditions, a cut part of the cannabis plant, typically from the main stem or a lateral branch, has the ability to produce roots and develop into a whole new plant, genetically identical to the mother. In cannabis, the production of roots may take anywhere from 5 to 21 days.
The oldest method of cannabis propagation is water cloning. Used for nearly as long as agriculture has been a part of human development, one simply sticks the cut end of clone into a small body of water like a glass or bowl and waits. Water cloning can take longer to show roots, but is a truly natural way to propagate any plant that is able.
Marijuana growers often root clones in peat pellets or in rock wool. Another technique that has become popular for rooting clones is aeroponic cloning.
The main steps of hormonal cannabis cutting are as follows:
  1. Part of the main stem or lateral branch up to 20 cm long is dissected in a non-vertical manner. The bottom 2/3 of leaves are removed.
  2. The cut end is brought to contact with rooting hormone, according to instructions, to promote root growth and inhibit fungal infection.
  3. The cutting is placed in an appropriate initial medium such as common soil, compost, perlite, vermiculite, peat moss, sand, rock wool, oasis foam or a combination of those. The initial medium is kept moist and high humidity is maintained in the surrounding air. Elevated humidity levels slow the transpiration rate and prevent the cutting from drying out. Mold is a common hazard due to the higher humidity and stressed cutting. During this phase, the temperature is kept relatively low and direct light is avoided so that the cutting does not dry out. The production from the slower photosynthesis is put into root production.
  4. After initial root development is evident the cutting is ready to be transplanted into its final grow medium. The high humidity environment is no longer necessary.

    Waste products

Prior to the establishment of the first legal cannabis market in Colorado, United States, growers of the plant in the American State of Washington experimented with the use of cannabis waste for pig food. In early 2013, potent cannabis waste products were mixed into the feed of four pigs during the last four months of their lives, resulting in a weight increase of to that was registered before the pigs were sent to slaughter in March 2013. Washington State's draft regulations prescribe that cannabis waste must be "rendered unusable prior to leaving a licensed producer or processor's facility," and adds that mixing it with food waste is acceptable. The European Food Safety Authority reported in 2011 that "no studies concerning tolerance or effects of graded levels of THC in food-producing animals have been found in literature." The agency also noted that "no data are available concerning the likely transfer of THC... to animal tissues and eggs following repeated administration."