As with any crop, knowing the humidity that the plant thrives in is important when designing a greenhouse. While cannabis in the vegetative stage actually likes a higher humidity level, it prefers lower humidity when in flower.
Greenhouse manufacturers who understand this can help you build flexibility into your greenhouse designs. There are several dehumidification units on the market, and for areas needing the ability to add humidity misting systems can be added into the greenhouse design. Ventilation recommendations for greenhouses tie into temperature and humidity needs. Greenhouse ventilation breaks down into two main categories: 1 natural ventilation covers roof vents, sidewall vents and rollup sides, and 2 forced air ventilation requires mechanical systems like exhaust fans, and sometimes cooling pads.
Please note that cooling pads are not a good option for high humidity regions. In addition to ventilation to remove hot air from inside the greenhouse, most greenhouse growers put airflow fans inside the greenhouse to circulate air movement which is good for keeping healthy plants. Greenhouse manufacturers can provide you with a greenhouse plan layout showing fan locations that optimize airflow coverage. Adjusting lighting levels will increase yields in a cannabis greenhouse.
One of the biggest advantages that greenhouse growing offers over indoor growing is that greenhouse plants benefit from natural sunlight. Having said that, when cannabis is in the vegetative state it performs best with around 18 hours of light. For this reason we recommend greenhouse growers include supplemental lighting in their cannabis greenhouse plan. Make sure your greenhouse lighting plans satisfy year round production if you want to optimize yields. Flowering cannabis needs blackout. While the vegetative stage enjoys greater light levels, for flowering longer periods of darkness are desired.
Ensuring 12 hours of uninterrupted darkness inside your greenhouse will force the marijuana plants to flower according to your production schedule. This is best achieved by utilizing blackout curtain technology, also known as light deprivation in the marijuana industry.
Blackout has been commonly used in production greenhouses for decades for poinsettias, kalanchoes, mums and other crops that benefit from photoperiod adjustments. Blackout curtains can cover flat roof areas running truss to truss on gutter connected greenhouses, or they can be sloped to follow the roof line of freestanding greenhouses.
Remember to cover sidewalls and door openings, and at GGS we provide light traps for exhaust fans as well. Cannabis plants thrive with CO2 enrichment. If you are using a hot water heating system CO2 can be pulled off the boiler. In other cases you may wish to use liquid CO2 to dose your cannabis crop.
This is an area best discussed with greenhouse heating experts like our sister company Niagrow Systems. Additional considerations include connecting your greenhouse to warehouse and office facilities for packaging, shipping, and other support functions. There are other unique requirements for cannabis that you will not have encountered with typical horticultural crops, such as drying rooms and vaults. Work with a company that has the expertise to help you. Cannabis Guide to Cannabis Production. The 4 Stages of Growth for Cannabis Production Affect How You Zone Your Greenhouse Zone 1: Marijuana mother plants Zone 2: Marijuana clones cuttings Zone 3: Marijuana in the vegetative stage Zone 4: Marijuana in the flower stage Plan for Expansion From the Start If you are already growing crops successfully in a greenhouse, it is easy to focus your cannabis business energies on the crop growing side.
Balance Production Efficiencies Marijuana growers are used to growing in smaller spaces than most commercial growers. Building the Ideal Environment 1. GGS has been building greenhouses for growers around the world since Learn more at www. 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. Pre-flowering indicates the plant is ready to flower. The flowering phase varies from about 6 to 22 weeks for pure indicas with their shorter flowering time than pure sativas. 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 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. The next phase consists in the fruition or fruiting : the females inflorescences that were not pollinated i. 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 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.
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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.
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 grey 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. 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. In the first weeks of flowering a plant usually doubles in size and can triple. During this time the buds greatly increase in weight and size. 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. In most places of the subtropics , cannabis is germinated from late spring to early summer and harvested from late summer to early autumn.
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. Growers cultivate on their own property or practice guerrilla farming i.
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 North Coast of California and British Columbia being particularly notable , but southern locations such as Maui, Hawaii 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. Some government agencies, including the Drug Enforcement Administration DEA , 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 as of [update]. 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 hour light, additional atmospheric CO 2 , and controlled humidity which allows freer CO 2 respiration. Plants can also be grown indoors through the use of hydroponics. To grow plants indoors, a growing medium e. 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 k.
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 some prefer long days and short nights and others preferring the opposite, or something in between. 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.
Reflectors are often used in the lamps to maximize light efficiency . At a medium growing density of 15 plants and watts per square meter, electricity costs are not insignificant. 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 0.
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 measured in PAR watts 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 often Mylar or Visqueen , or alternatively, white paint to maximize efficiency. 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 which also reflects heat , and Foylon a foil-laminated, reinforced fabric.
When growing indoors, the cultivator should maintain as close to an ideal atmosphere inside the grow-room as possible. Adequate levels of CO 2 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 CO 2. Ways of increasing carbon dioxide levels in the grow-room include: bottled carbon dioxide, carbon dioxide generators, a milk jug and yeast solution in which yeast grows in a container thereby emitting CO 2 , a baking soda and vinegar mixture in a container, or dry ice. Certain plants e.
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. Ozone itself has a distinctive smell and is harmful to living things, although the molecule breaks down quickly 20 minutes to an hour 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. Some growers will construct grow cabinets made out of an old refrigerator, cabinet, dresser drawer or similar.
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 growing operations, often located in grow houses 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.
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More expansive grow-ops are generally more susceptible to detection than smaller operations. Because individual grow light power generally ranges from watts to 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 e. 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.
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.
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.
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Home inspectors routinely fail to detect tell-tale signs that a house had been used as a grow-op. 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. This is seen under a 30xx microscope by examining the trichomes on the flowers.
When trichomes are undeveloped they are completely clear. Harvesting before most trichomes have turned white may reduce the overall potency and efficacy time. The plants are dried at room temperature in a dark space. 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. 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. These will be evaporating and likely discernible to others anywhere in the vicinity of the general area. In less populated areas with good air movement dissolution and dispersal techniques for odor management may be employed i.
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. A simple way to check this is by closing the cannabis up in an airtight glass container with a hygrometer. 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 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 bud, stems and seeds 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.
Outdoor growers are likely to confront issues regarding pests. In any case indoor or outdoor , 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. Indoor growers also have problems with pests, usually caused by the grower or a pet bringing them in from the outdoors. If caught too late, eradication of many destructive insect species indoors may be impossible until all infected plants are removed from the space and sterilization methods employed.
The modification of a plant's growth habit is called training.
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Indoor cultivators employ many training techniques to encourage shorter plants and denser canopy growth. Some cultivators employ plant training techniques to increase yields indoors:. Topping is the removal of the top of the apical meristem dominant central stem , called the apex or terminal bud, 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 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 also called "FIMing" 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 s 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. 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 , LST'ing can be used to keep all growth tips meristems 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 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.
In contrast to the "Screen of Green" method, Sea of Green or SOG growing depends on the high density of plants as high as 60 per square metre or 6 per square foot 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.
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. 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. Because of the amount of plant required to fill the net, the vegetative period may require longer than normal to be ready for flowering.
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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.