Cultivation requirementsIn order to prosper, cannabis needs the following:
Growth mediumAlmost always soil is deployed, although some advanced growers use hydroponics. An ideal soil for cannabis has the following characteristics:
- Loam texture to ensure good drainage, which facilitates nutrient absorption and prevents root drowning.
- Sufficient nutrients. Commercial soil bags usually indicate as "N-P-K = x%-y%-z%" the percentages of the fundamental nutritional elements, i.e. Nitrogen, Phosphorus and Potassium. Nutrients are often provided to the soil via fertilizers but such practice requires caution.
- pH between 6.0 and 7.0. This value can be adjusted - see soil pH. Commercial fertilizers (even organic) almost always make the soil more acidic (decrease its pH).
WarmthThe optimal day temperature range for cannabis is believed to be 24 to 30 °C (75 to 86 F). 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, although some strains have been observed to withstand frost temporarily.
LightLight can be natural (outdoor growing) or artificial (indoor growing).
When artificial light is used, from the germination until the flowering stage, the plant typically remains under a regime of 16 – 20 hours of light and 4 – 8 hours of darkness. When the plant reaches the flowering stage the regime is typically switched to 12 hours of light and 12 hours of darkness.
WaterWatering 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 texture. A conspicuous sign of water problems is the downward wilting of leaves.
Nutrientsfertilizer). Commercial fertilizers must indicate the levels of NPK (mentioned above). During vegetative stage cannabis needs more amounts of N than of P and K while during flowering P is more essential than N and K. The presence of secondary nutrients (Calcium, Magnesium, Sulfur) is recommended. Also there are seven micro nutrients (Iron, Boron, Chlorine, Manganese, Copper, Zinc, Molybdenum) that are not extremely important and rarely manifest as deficiencies.
Fertilizers although vital for good cannabis growth, must be used frugally otherwise they could burn the plant. As a general rule, half the amount suggested in a bottle may be given each time.
As a plant acclimatized to virtually every growing region on Earth, its nutrient needs vary widely with its genetics and can truly only be determined with experience. Chemical plant foods vary greatly maker to maker, and some can be used at full strength, or the strength listed for plants with large fruits like the tomato.
Stages of development
Germinationmetabolic processes such as the activation of hormones which in turn trigger the expansion of the embryo within the seed. Then the coating cracks open and produces a small embryonic root that begins growing downwards due to gravitropism, if placed in a proper growing medium. Soon (after 2–4 days) the root is anchored and two circular embryonic leaves (cotyledons) emerge in search of light, as the remains of the seed shell are pushed away. This marks the beginning of the seedling stage.
Seeds may be germinated by soaking them between wet paper towels, in a cup of water at room temperature for 24 hours, or in wet peat pellets. Regardless of the method used however, distilled water is often employed since it has the proper pH. In most cases tap water is sufficient. Peat pellets are often used as a germinating medium as they make it unnecessary to transplant the fragile seedlings; the saturated pellets with their seedlings can be planted directly into the intended growing medium with a minimum of trouble and effort, or shock to the plant.
A technique that achieves high germination rates is the following: First the seeds are inserted into a cup of water. All will initially float over the surface so forcing them to immerse completely is recommended. Then the cup is left in a warm dark place for no more than 24 hours (otherwise seeds might drown). Shortly most will go down the bottom, an indicator that water has penetrated the shell. Finally, the seeds are placed carefully in a constantly damp, warm and dark environment such as wet cotton or towel. Dirty hands (even traces of nicotine on them) can damage the seeds. As soon as the root can be distinctly seen, the seeds are ready to be placed in a growing medium.
The plant can begin to sex itself in this stage but if time is an issue one can induce sexing by switching to a 12/12 hour period. Once sex is determined you can remove the males and switch the cycle back to vegetation stage by inducing an 18/6 hour period.
When the plant possesses 4 sets of true leafs and the 5th is barely visible in the center of the growth tip, or shoot apical meristem (SAM), the plant has entered the vegetative phase of growth. During the vegetative phase of growth, the plant directs its energy resources primarily to the growth of leaves, stems, and roots. A strong root system is imperative, as it 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. The males are then usually culled when they are identified, because if males are allowed to pollinate the females, both the potency of the female flowers and the amount of usable plant material will be greatly reduced, as energy that would have been used to make large, potent buds instead goes to making seeds.
During the vegetative phase of growth, cultivators generally employ an 18 to 24 hour photo period, as the plants grow more quickly if they receive more light, although a warmer and cooler period are required for optimal health. While 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.
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 you're flowering in and how many plants you wish to flower at once and how big your strain gets in 'the stretch' - the first two weeks of flowering.
Marijuana cultivators employ fertilizers high in nitrogen and potassium during this 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.
The modification of a plant's growth habit is called training. Indoor cultivators employ many training techniques in order to encourage shorter plants and denser canopy growth. For example, unless the crop is too large to be extensively pruned, cultivators will 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.
Many cultivators also employ other techniques:
Is done by removing the top of the apical meristem (dominant central stem), called the apex or terminal bud, in order to transfer apical dominance (the tendency for the apex to grow more rapidly than the rest of the plant) 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 almost infinitely, but over-diffusion of apical dominance will produce 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 (also called super cropping) is similar to topping in that it causes the lower branches to grow more rapidly, but the apical meristem will maintain apical dominance, which is especially useful if the plant has already been topped. Pinching is performed by firmly pinching the apical meristem(s) so as to substantially damage vascular and structural cells but without totally breaking the stem. This will cause the lower limbs to grow more rapidly while the pinched tissue heals, after which time the stem will resume apical dominance.
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 (Inverse-square law) LSTing can be used to keep all growth tips (meristem) 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 (side shoots), topping is often done a few weeks before beginning LSTing. LSTing works by changing the distribution of hormones, more specifically Auxins, in the plant.
Pre-flowering phaseDuration: 1 day to 2 weeks. Also called 'the stretch'. In most plants will last for 10–14 days after switching the light cycle to 12/12. The plant development increases dramatically, with the plant doubling in size or more (see reproductive development below). The production of more branches and nodes occurs in this stage as the structure for flowering is built. The plant will start to show calyx which appear where the branches meet the stem (nodes). Pre-flowering indicates that the plant is ready to flower.
Reproductive/Flowering phasephoto period) will flower under diminished light. In nature, cannabis plants sense the forthcoming winter as the earth rotates around the sun and daylight reduces in duration (see also season). If females are not pollinated (fertilized by male pollen) they will start to produce buds containing sticky white resin glands or trichomes in a final attempt to attract male pollen. The trichomes contain the largest amounts of THC and CBD, the two main psychoactive substances. Indoors, flowering is induced by keeping the plant in complete dark for 12 hours every day, until it is ready to be harvested. If manipulated, a female can either generate a seedless bud, a bud with a few seeds, or a bud that is almost totally seeds. The first case is achieved by removing all the male plants before any of their flowers open, the second occurs when one or more male flowers have barely burst open and then removed and the third case occurs if the males are let to fully pollinate the females.
Buds of the first case are called sinsemilla (it is really two words: "sin semilla," which translates to "without seeds" in Spanish, but is often misspelled as one word). The resultant cannabis contains the most Cannabinoids possible. The amount of Cannabinoids in sinsemilla is considerably more in comparison to cannabis that has been grown in a pollinated environment, because the production of seeds requires an immense amount of energy, and if left unpollinated a female plant will divert all her energy to calyx production in an effort to seize pollen, This is especially desirable, as the calyx is where the highest concentration of trichomes exists, and the more densely packed a plant is with calyces, the greater psychoactive effect that plant will likely have. Potent sinsemilla is especially important to medical users, to minimize the amount of cannabis they must consume in order to be afforded relief. Cannabis with seeds is generally considered to be of inferior quality and/or grown with inferior technique. Common terms for seeded, or otherwise low-quality, cannabis are schwag, "regs," "booty," "greta," "bushweed" or mersh.
Indoors, plants like cannabis are induced into flowering by decreasing its photo period to at least 10 hours of darkness per day. Traditionally most growers change their plants lighting cycle to 12 hours on and 12 hours off. This change in photo period 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 come fall and winter.
While the flowering hormone in most plants (including cannabis) 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 flower with 12 hours of darkness to be safe.
The flowering hormone is very quickly inhibited, taking less than two minutes of exposure. Thus, many cultivators are vigilant that no light reach their plants during the flowering phase, some going so far as to research the phases of the moon to avoid exposure to the full moon during critical phases of flowering. Indoor growers often seal the area in which their plants are growing in an effort to make the space light tight, and are careful not to "peek" at the plants during their dark phase.
Flowering usually lasts from 45 to 90 days indoors. If growing outdoors it may take somewhat longer, depending on the natural onset of the colder seasons. The flowering length is mainly genetically determined with some plants (as pure cannabis "indica" strains) flowering in as low as 45 days, while some plants (as cannabis "sativa") can take up to 4 months to finish and the harvest yields significantly less. This is also the main reason why certain plants (as cannabis indica) are almost always grown indoors (unlike cannabis sativa, which is also grown outdoors).
Some plants, specifically members of the subspecies Ruderalis, will begin the flowering cycle without a significant reduction in their photo period.
Flowers from certain plants (e.g. cannabis) are called Calyx, and are (with cannabis) the most prized part of the plant. In late flowering the calyx are easily visible to the naked eye. Calyx development begins approximately 1–2 weeks after the photo period is reduced. In the first weeks of flowering a plant usually doubles in size and can triple. Calyx development ends around 5 weeks into flowering and is proceeded by a period of Calyx “swelling”. During this time the buds greatly increase in weight and size.