Cannabis belongs to the genus Cannabis in the family Cannabaceae and includes three species, C. sativa, C. indica, and C. ruderalis. It is usually a dioecious (each individual is either male or female) annual plant unless its epigenetics trend it towards hermaphroditic characteristics. The plant is indigenous to central Asia and the Indian subcontinent.
Cannabis strains are either pure or hybrid varieties of Cannabis, typically of C. sativa, C. indica and C. ruderalis. Varieties are developed to intensify specific characteristics of the plant and terpene profiles. Variety names are typically chosen by their breeders, and often reflect properties of the plant such as taste, color, smell, or the origin of the variety. Cannabis strains commonly refer to those varieties with recreational and medicinal use. These varieties have been cultivated to contain a high percentage of cannabinoids.
C. sativa is relatively tall (reaching as high as 4.5 meters), with long internodes and branches, and large, narrow-bladed leaves. C. indica varieties are shorter and bushier and have wider leaflets. They are often favored by indoor growers for their size. Sativas bloom later than indicas, often taking a month or two longer to mature. C. ruderalis is a very short variety due to its autoflowering characteristics. It typically grows 1 to 2.5 feet tall.
Soil VS Hydroponics
When comparing soil and hydroponics, you must first understand how a plant grows in both conditions. With hydroponics, you feed the plant directly, when gardening in soil, you feed the soil, which then feeds the plant. Soil is a living micro-ecosystem that functions quite differently than hydroponic media. While some growers treat soil simply as an inert media which holds chemical and salt based fertilizers, it is in our interest to diverge from those methodologies. In living soil, highly complex microbiology interact with the plants roots to facilitate growth . In hydroponics, an inert media provides the plant with all the chemical nutrients it requires. In hydroponics, you actively manage what nutrients are fed to the plants on a daily basis. Clearly advances are being made in hydroponics and organic fertilizers and biological additives are making headway.
In general, hydroponics typically produces larger yields indoors but can be incredibly sensitive because there is much less of a buffer than with conventional soil gardening. Hydroponic plants left without water for one day can be COMPLETELY FRIED whereas soil plants may experience drooping, some mild burning, but will usually bounce right back. These are the generalizations between soil and hydroponics.
There is an increasing growing number of soil companies offering premium potting soil in the marketplace. The medium of potting soils can range widely.
A typical example of an all purpose soil, such as Roots Organics, has the following composition:
Perlite, Coco Fiber, Peat Moss, Composted Forest Material, Pumice, Worm Castings, Bat Guano, Soybean Meal, Alfalfa Meal, Fish Bone Meal, Kelp Meal, and Greensand
A soilless potting mix is a growing medium used as a soil substitute. It is a mixture of various raw materials that does not contain any soil at all. Most soilless potting mixes are predominately sphagnum peat moss. Due to recent environmental concerns over how peat moss is harvested, many have moved over to coconut coir fiber. Other materials like grow rocks, expanded clay pellets, silica rocks, vermiculite and perlite can all be used.
Most soilless mixes require more fertilization on a regular basis. The individual will need to supplement with an all purpose fertilizer plus additional micro nutrients to synthesize the trace elements.
Currently, our investigation supports the model that cannabis requires about 20 elements to support all of its biochemical needs. These 20 elements are called essential nutrients. Carbon, hydrogen and oxygen are the three backbone elements that are considered non-mineral elements which allow plants to undergo photosynthesis. Those three elements account for around 95% percent of the mass of the plant. On average, the dry weight (excluding water) of a cell is 50 percent carbon. That makes 17 additional elements to discuss.
Nitrogen, potassium, phosphorus, calcium, magnesium and sulfur are considered macro-nutrients. These six elements are used in relatively large amounts by the plant. There are ten other elements that are used in much smaller amounts and are called micro-nutrients, or trace elements. The micro-nutrients are iron, zinc, silicon, molybdenum, manganese, boron, copper, cobalt, sodium, chlorine and nickel. All 17 elements, both macro-nutrients and micro-nutrients, are essential for plant growth. Some of the micro-nutrients, such as cobalt, are required at such trace levels that they are normally present in residual amounts and are not included in fertilizers. Other trace minerals, like iron, are so important for plants, that many supplements and fertilizers will contain added iron. For further information on plant nutrition visit our Nutrients Page.
Mobile nutrients are capable of moving from one part of the plant to another when a nutrient shortage occurs. That means that any imbalance will typically show deficiencies or toxicities on the older leaf surfaces. The mobile nutrients are: Nitrogen, Potassium, Phosphorus and Magnesium.
Immobile nutrients are not readily capable of being translocated to other areas of the plant. This means that these symptoms will typically show up on the newer leaves. The immobile nutrients include: Silicon, Sulfur, Calcium, Iron, Boron, Chlorine, Copper, Cobalt, Manganese, Molybdenum, Zinc.
Nutrient soil amendments (fertilizers) 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 N-P-K (Nitrogen, Phosphorus, and Potassium). During the vegetative stage, cannabis needs more N than P and K, while during the flowering stage, P is more essential than N and K. Fertilizers provide both macro and micro nutrients required for plant growth. Please reference our organic fertilizers for more information.
The temperature of your grow room plays a very important role in the growth of your plants and the quality of product produced. It is important for gardeners to understand how controlling temperature also optimizes harvest. There appears to be a striking contrast with indoor versus outdoor grown temperature regulation. Indoors has a very specific range of temperature that it operates under. Indoors, the optimal day temperature range is 70º-75º F without carbon dioxide and 80º-85º with carbon dioxide. Outdoor and greenhouse grown cannabis can handle remarkably hotter temperatures than indoor grown cannabis. In the summertime in certain parts of the emerald triangle, temperatures consistently reach 100º days and plants seem to thrive when properly hydrated. Greenhouses, with both end walls removed, can maintain similar temperature patterns to full sun plants. Indoors, temperatures above 88º F (31 °C) will slow growth.
A plants metabolic rate will slow down at temperatures below 60º F. If temperatures fall below 40º F (4º C), cannabis plants will experience tissue damage. Certain strains, dominated by C. indica, are more adapted to colder climates can handle cooler temperatures.
Light can be natural (outdoor growing) or artificial (indoor growing). Natural lighting is the clear winner
Under artificial light, the plant typically remains under a regime of 18 hours of light and 6 hours of darkness from the germination until flowering. Some growers prefer to keep the plants under longer intervals of daylight hours. Although the plant can undergo a photoperiod of 24 hours of light without harm, there is an ongoing debate over the importance of the "dark period". 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. Additionally, plants kept under 24 hours of light may become more sensitive to outdoor photoperiods. For example, a clone under 24 hours of light placed outside towards the end of May may start flowering as opposed to another clone who received only 18 hours of light.
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. Some Sativa strains require up to 13 hours of darkness to start flowering.
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. Too much water can kill young cannabis plants and can create a condition called damping off.
Depending on the source of the municipal water supply, the additives in tap water can cause irregular nutrient lockouts and the chlorine and/or chloramine added can damage the soil biology. The additives can be removed with reverse osmosis filtration.
Stages of development
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 (because of 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 and the remains of the seed shell are pushed away. This marks the beginning of the seedling stage.
Germination can be initiated by a number of different methodologies. You can soak seeds either between damp paper towels, in a cup of water at room temperature, in wet peat pellets, in hydroponic media like rockwool or directly in potting soil. Seeds can be planted directly into the soil given that they have the correct environment to thrive. Direct planted seeds usually thrive when inside a greenhouse or grow room with some climate controlled features like heating mats.
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.
Many 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. However, in cooler climates HPS lighting can help keep the room warm which turns into a beneficial source of heat.
The plant will naturally begin to develop identifiable sex characteristics in this stage after 4 to 6 weeks, but some growers will hasten this by switching to a 12/12 hour light period for 1-2 weeks to induce flowering. Once sex is determined and the male plants are removed they will return the plants to the vegetation stage with an 18 hour light period. Some gardeners choose to sex the plants by taking a clone of each seedling, root it, and force flowering in a separate growing area.
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. Concurrently the root system expands downwards in search of more water and food. Some newly developed strains (auto flowering hybrids) omit the vegetative stage and pass directly from seedling to pre-flowering.
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 typically needs 1 or 2 months to mature before blooming. However, there are many variables that can alter this vegetative period. Certain indoor gardeners growing hydroponically can transplant clones and only vegetate for several weeks before they induce flowering. Other factors will determine on how long of a vegetative period the gardener chooses for their plant. One of those factors are strain characteristics, indica vs. sativa. Indicas are typically short and bushy and do not stretch as much during flowering. Sativas on the other hand are notorious for doubling or even tripling in height. So a grower with a sativa dominant strain might want to induce flowering when the plant is only 12" since will be close to 3' tall when done. It is up to the individual to find out as much information about a particular strain to help optimize their conditions.
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. (CHA will be releasing advanced articles on this as we grow) 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" (i.e., the first two weeks of flowering).
Cannabis cultivators employ fertilizers high in N (nitrogen) and K (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.
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. (See reproductive development below.) 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 (nodes). It is very important to ensure the plant has well balanced nutrients during the preflowering phase as this will set the stage for overall yields.
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 the flowering phase. Males produce little ball-like flowers clustered together like grapes called panicles. Most plants (except auto flowering strains that flower independently of photoperiod) 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 (see also season). If females are not pollinated (fertilized by male pollen) they start to produce buds that contain sticky white resin glands or trichomes in a final attempt for pollination by windborne male pollen. The trichomes produce resins that contain the varying ratios of cannabinoids depending on each strains genetic profile. 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 (which translates to "without seeds" in Spanish, and is often misspelled as one word). 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. 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 (generally October), whereas other strains are just finishing flowering, and may suffer from botrytis (gray mold) 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 (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 use 12 hours of darkness.
Flowers from certain plants (e.g. cannabis) are called bract/bracteole, and are (with cannabis) 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.
Like most plants, cannabis has the potential for vegetative propogation with the most common and simple method being cutting. A cutting is another word for cloning, since, the branches are cut off the mother plants. 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 (the clone), 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 (cutting) 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 (compressed peat moss) or in rock wool. Another technique that has become popular for rooting clones is aeroponic cloning.
- Start with a strong healthy mother plant. Ensure that she is free of pests and disease as they will transfer to the clones and compromise the entire process.
- Gather your necessary materials. Typical supplies include: rooting compound, propagation tray, heat mat, grow plugs, water, pH solution, clean scalpel, shot glass and rubbing alcohol.
- After the equipment has been properly sterilized and your cloning room has been set up, you are now ready to begin the cloning process.
- Start by making a clean 45 degree cut across part of the main stem or lateral branch. The length of the cuts can range from 3-7 inches long. If you are taking cuts one at a time then dip directly into the rooting compound and insert into grow plugs. (*Note: Never dip cut directly into the bottle of rooting compound if you plan on reusing the bottle at a later date! Always transfer the rooting compound into a separate shot glass first.)
- If you are taking multiple cuts at once, have a cup of water nearby that you can place multiple cuts into at once. Placing them in the water first prevents air bubbles (embolisms) from lodging in the stems.
- Once you have a number of fresh cuttings in the cup of water, you want to remove the lower sets of leaves, the average rule of thumb is removing the lower 2/3 of the cut. If the top leaves are very large, you may also cut of those tips. The goal in this step is to keep the plant from loosing too much water water during transpiration, focusing its energy on rooting instead.
- 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 (water loss from leaves) and prevent the cutting from drying out.
- Place the tray under proper lighting, such as a T5 fluorescent or compact fluorescent lamp (CFL) for 18-24 hours light per day. Keep clones under a humidity dome and try to maintain a relative humidity from 80-100%. After the first 24-48 hours have passed, open the domes at least once a day to air our for 30 seconds at a time. This prevents any excess moisture from creating pathogenic conditions. As an alternative to humidity domes you can mist the clones multiple times a day with water.
- Never let the grow plugs dry out! Monitor them throughout the week to ensure they stay moist, but not soaked.
- After 7-14 days, inspect the bottom of the plugs for roots. After initial root development is evident, the cutting is ready to be transplanted into its final grow medium.
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.
The series of photos below show the transition of outdoor cannabis plants from May-September. Under optimal conditions, a three foot tall plant (planted in late May) will grow between 12-15 feet tall and produce 3-10 pounds depending on strain characteristics and nutrient regimens.
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 (cerebral) high, better response to sunlight, and lower odor emissions.
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 late May or early June to provide plants a full four months of growth. Harvest is usually between mid September and early October.
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. Follow our BLOG to get the latest updates on our tours of big outdoor gardens in Humboldt County!!!
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. The environment in which your plants are grown is one of the most important factors affecting the quality and size of your yield. The temperature and humidity varies and the lighting has to be of sufficient intensity.
One of the major advantages of indoor gardening is that it allows you to create and control the climate within the grow room. This allows you to supply your plants with ideal conditions for healthy growth, ensuring an optimal yield. All healthy plants require a good supply of water and balanced nutrients. They need the right temperature, fresh filtered air and good carbon dioxide rates to produce clean and heavy yields.
Plants can also be grown indoors through the use of hydroponics.
To grow plants indoors, a growing medium (e.g. soil or growing substrate), water, nutrients, light and air need to be supplied to the plant (with the exception of aeroponic cultivation, in which case a growing medium is not required).
There are many different plant grow lights available. To determine the appropriate lighting, the specific needs of the plant must be considered, as well as the room size and ventilation.
Most plants grow under most light spectra, but always prefer a full spectrum light. Certain tests performed found that when a room was set up using both high pressure sodium (HPS) and metal halide (MH) lamps, the plants in between the two lights did better than those under MH alone but not as well as those under HPS. However, certain plants (as cannabis) can be grown successfully under both types of light. MH is used for the vegetative phase of growth, as it encourages short inter nodes (distance between sets of leaves), and inhibits cell elongation, creating a shorter, stockier plant. Metal halide lamps produce more ultraviolet radiation than high pressure sodium lamps, which may play a role in increasing the flowering (and for certain plants such as cannabis, the amount of psychoactive substances as THC) of the plant. High pressure sodium lamps trigger a greater flowering response in the plant and are thus used for the second (reproductive) phase of the growth, or they are used by those people who only wish to purchase a type of single lamp. If high pressure sodium lamps are used for the vegetative phase, plants usually grow slightly more quickly, but also have longer inter nodes, and may be taller.
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 (PAR) of the spectrum.
This section will show you the different types of lighting systems.
Fluorescent lights don't give off much heat but they're also not as intense so they need to be closer to the plants. Under proper conditions it is possible to keep fluorescent lights only inches away from the top canopy. Typically they are used for younger vegetative growth and suitable for germinating and raising seedlings. They do not provide enough photo-synthetically active radiation to support robust and vigorous growth during flowering. While plants can flower under fluorescent lights, the yields will be substantially lower.
There are many different types of fluorescent tubes. The differences are usually defined based on their physical size, the composition of phosphor and wattage. The phosphor chemistry is what determines the difference between a cool white and daylight tube.
Induction lamps are basically fluorescent lamps with electromagnets wrapped around a part of the tube or inside the lamp. Because induction lamps do not contain metal electrodes, which are the most common source of failure, induction lamps can have a lifespan of 80,000 hours.
HIGH INTENSITY DISCHARGE (HID) LIGHTING
HID lighting produces much more light than a fluorescent bulb. These lamps require more electricity and must be cooled, as they get very hot and will easily burn your plants. The quality of light emitted by HID lights is closer to that of natural daylight. There are two types of HID grow lights used for horticultural lighting, Metal Halide (MH) and High Pressure Sodium (HPS).
Metal Halide (MH) bulbs produce light primarily in the blue spectrum, which is best suited for vegetative growth. The average lifespan is typically around 10,000 hours. MH lights are less suitable for the flowering and fruiting stage of edible and ornamental crops, so either switch to HPS or use a combination of the two.
High Pressure Sodium (HPS) lights emit the yellow and red regions of the light spectrum so they are best suited for the flowering stage. HPS lights are ideal for indoor gardening and greenhouse applications because they give off a warm spectrum light, which mimics the harvest sun. Plants love these bulbs because they simulate real sunlight conditions and encourage rapid fruiting, flowering and budding.
When using HPS lighting in the vegetative stage, plants can become elongated and leggy than when using a metal halide light. Exposing plants solely to a red spectrum light tends to make them stretch. Standard HPS bulbs that are not intended for horticultural use often lack blue spectrum light. For optimal results, use an enhanced performance HPS grow light, such as the bulbs made by EYE Hortilux Lighting. These bulbs have a wider color spectrum, which makes a significant difference in plant growth.
LIGHT-EMITTING DIODE (LED) LIGHTING
Advantages of LED over gaseous discharge lamp technology (HID Lighting) include the ability to provide high light intensities with low radiant heat, adjustable spectral quality that allows optimization to improve photosynthetic efficiency and plant form and function, good safety characteristics, and operating capabilities that can significantly reduce power use. Improvements in LED “chemistry,” mounting and packaging, electrically efficient device drivers, heat sinking, and optics (lenses and reflectors) will all contribute to advances in LED lighting systems. The optimistic outlook for solid-state lighting technology along with the advantages it provides over existing lamp types makes LEDs a prime candidate for use in protected agriculture. LEDs have a very long operating life; current LED technologies are rated as maintaining 70% of their original luminous output after 50,000 h, and this is probably a conservative number as long as the devices are cooled adequately.
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 (18 degrees F) 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 (CO2). Ways of increasing carbon dioxide levels in the grow-room include: bottled carbon dioxide, carbon dioxide generators, a baking soda and vinegar mixture in a container, or dry ice.
Female cannabis plants emit a distinctive odor during their reproductive phase. This presents difficulties to those who are cultivating in urban areas and may prefer to mitigate odors. 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 people present.
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.
Harvesting, drying and curing
Cannabis buds are typically harvested when fully ripe. Generally, ripeness is defined as when the white pistils start to turn dark yellow, orange, light to mid red, etc. and the trichomes, (vernacular: crystals), barely begin to turn milky from clear. These trichomes can range from completely clear (generally deemed underdeveloped), to amberish-red. Ideally, professionals use a decent power magnifying glass, a brix meter to measure "sugar" content, and a microscope. Harvesting slightly early will maximize the THC content. Harvesting later reduces the THC content and maximizes the sleep inducing effect desired by some medical users.
The plants are dried at room temperature in a dark space. It is actually optimal to keep the temperature between 60 and 70 °F (16 and 21 °C) because many terpenoids evaporate at temperatures beyond 70 °F (21 °C). 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.
There are quite a few different methods for drying. Some believe flowers should be hung by their stalks, allowing the internal fluids of the plant to remain in the flowers. Some wet trim and hang the flowers in baskets. 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.
The curing process continues breaking down sugars and helps develop taste and smoothness of smoke. Usually, the dried product stored in an airtight container. Initially, the product is checked periodically to make sure it was properly dried and has not re-moistened itself. After several days, when the product is dried to satisfaction, the containers are sealed off and opened just once a week. Curing can be a highly varied process depending on environmental conditions, generally the minimum time is usually two weeks. 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 containers are stored in a cool, dark place. Failure to vent the container causes moisture buildup that leads to moldy flowers!!!
Pests and pathogens
At some point, growers are likely to confront issues regarding pests and pathogens. In any case (indoor or outdoor), the CHA recommends extreme caution when using chemical pesticides/fungicides, for they may have toxic effects on the environment, the plants themselves and in turn cannabis consumers. As a general rule of thumb, the CHA recommends using OMRI listed controls as the mandate for deployment of pesticides clearly marked as "safe to use on food crops".
We will expound on these topics as our website evolves. Please joining our MEMBERSHIP to be provided in depth answers for pest/pathogen Management and further information on Integrated Pest Management.
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