Websites:  Grow Weed Easy

Books/References on Growing Cannabis:

Details of existing Cannabis plants varieties and breeding methods are described in Potter et al. (2011, World Wide Weed: Global Trends in Cannabis Cultivation and Its Control), Holland (2010, The Pot Book: A Complete Guide to Cannabis, Inner Traditions/Bear & Co, ISBN1594778981, 9781594778988), Green I (2009, The Cannabis Grow Bible: The Definitive Guide to Growing Marijuana for Recreational and Medical Use, Green Candy Press, 2009, ISBN 1931160589, 9781931160582), Green II (2005, The Cannabis Breeder’s Bible: The Definitive Guide to Marijuana Genetics, Cannabis Botany and Creating Strains for the Seed Market, Green Candy Press, 1931160279, 9781931160278), Starks (1990, Marijuana Chemistry: Genetics, Processing & Potency, ISBN 0914171399, 9780914171393), Clarke (1981, Marijuana Botany, an Advanced Study: The Propagation and Breeding of Distinctive Cannabis, Ronin Publishing, ISBN 091417178X, 9780914171782), Short (2004, Cultivating Exceptional Cannabis: An Expert Breeder Shares His Secrets, ISBN 1936807122, 9781936807123), Cervantes (2004, Marijuana Horticulture: The Indoor/Outdoor Medical Grower’s Bible, Van Patten Publishing, ISBN 187882323X, 9781878823236), Franck et al. (1990, Marijuana Grower’s Guide, Red Eye Press, ISBN 0929349016, 9780929349015), Grotenhermen and Russo (2002, Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential, Psychology Press, ISBN 0789015080, 9780789015082), Rosenthal (2007, The Big Book of Buds: More Marijuana Varieties from the World’s Great Seed Breeders, ISBN 1936807068, 9781936807062), Clarke, R C ( Cannabis: Evolution and Ethnobotany 2013 (In press)), King, J (Cannabible Vols 1-3, 2001-2006), and four volumes of Rosenthal’s Big Book of Buds series (2001, 2004, 2007, and 2011), 

Introduction/Definitions:

Typically, sun-grown Cannabis is planted in spring, flowers when night periods exceed about 10-12 hours, and is ready to harvest in late autum. 

Cannabis is a very rapidly growing plant, attaining a usual height of three to twenty feet at maturity. Cannabis is dioecious, which means that there are sexually distinct male and female plants. The known species are Cannabis sai/Va, Cannabis indica and Cannabis ruderatis with multiple strains in cultivation. 

Photoperiod refers to a plant’s response to the amount of light and darkness, to which it is exposed. Short-day or long-night plants, as obligate photoperiodic plants, will only begin flowering once the sunlight hours are reduced to a certain number, based on the seasonal changes of the earth’s orbit or artificial replication thereof. Typically, short-day plants will flower when the day is less than 12 hours (i.e., the night is longer than 12 hours) regardless of plant age or size. In indoor growing operations, this photosensitivity allows for a precisely tailored plant cycle for continuous growing seasons with the stages of development being artificially controlled. Additionally, when outdoors, short-day plants can be fooled into flowering early (i.e., outside of the natural seasonal schedule) by being covered for at least 12 hours in a 24-hour period. Similarly, if exposed to more than 12 hours of light in a 24-hour period, short-day plants will not flower, so flowering may be delayed and/or a plant may be kept in a perpetual vegetative state (e.g., as a mother plant for clones and/or seeds). (US 20230242932)

In general, a Cannabis plant has a vegetative stage and a flower stage. The latter may be initiated by substantially increasing the time the Cannabis plant essentially does not receive light (dark period). During the phase of life known as the vegetative stage (the first stage of life for marijuana), a cannabis plant grows like a weed. In the vegetative stage a cannabis plant essentially only grows new stems and leaves, and can grow several inches a day. When growing Cannabis indoors, the flowering stage begins when the lighting schedule is reduced to a 12/12 light cycle (12 hours light, 12 hours darkness each day). During the vegetative stage, the Cannabis plant should get horticulture light during at least about 16 hours a day. Getting those 12 hours of uninterrupted darkness each day may give the plant the signal that it is time to start flowering. The plant may receive a kind of winter trigger, because the days are getting short. On the internet, it is amongst others found that “if the plant gets any light during the dark period, even for just a minute, it will not make buds! A flowering plant may even revert back or express hermaphroditism if it gets any light at night”. During the first few weeks after being switched to a 12/12 schedule, the Cannabis plant will be growing relatively fast and may rapidly gain height. In fact, a Cannabis plant can almost double in height after the switch to 12/12. This period of super-fast and often stretchy growth is sometimes referred to as the “flowering stretch”. The female plants will start sprouting lots of white pistils, though they usually will not start growing “real” buds with substance quite yet. (US 20220295712)

With regard to some plants, as an example, such as cannabis, there are two key growth stages, a vegetative stage and flowing stage. To maintain the plant in the vegetative cycle, the lights may be kept ‘on’ eighteen (18) hours a day and turned ‘off’ six (6) hours a day. When the grower wants to flip the plant into the flowing stage or flower producing stage, light times may be changed to twelve (12) hours ‘on’ and twelve (12) hours ‘off’ in a 24-hour period. The change in light times activates the plant into what it perceives as a season change, thereby moving the plant into the flowing stage. US 10842082

Propagation:

In vitro Propagation:

In vitro propagation techniques offer efficient multiplication yields of disease free C. sativa L. plants at a commercial scale. Generally, such techniques eliminate cultivation space and reduce production costs and time. The products of these processes display genetic and phenotypic univformity. in terms of theri morphological trails, which include some of the majjor commerically important trails. Moreover, the method has tremendous potential for genetic transformation by modifying both the genetic information and the regulation of tose gene responsible for the production of valuable biolgoical active substances. (Mitsis, “An Alternative in vitro Propagation Protocol of Cannabis sativa L. (Cannabaceae) presenting efficient rooting, for commerical production” Plants, 2022, 11(10): 1333).

Traditionally, the conventional in vitro micropropagation prcoedure contains four stages, i.e., culture establishment, proliferation, rooting of shoots and acclimatization. In vitro rootingreported costs represent 35-75% of the total process. Gradually labor costs relating to conventional micropropagation, with the exception of culture extablishment, have reached about 60%. Cuttings, in teh frist three pahses,a re encldsed in vessels wtih apssive gas exchange, udner aseptic conditions, An upturn in tissue culture led to the onset of the phtooautotrophic micropropagation technqiue, in which chlorophyllous explants were grown under CO2-rich condtions. Moreover, culturing explants in vessels with gas-permeable film as enclosures, combined with the use of rockwool multi-blocks as a substrate were found to be suitable for the development of some plant species. Phtoautotrophic micropropagation on rockwool blocks as a substrate was efficient for C. sativa L. cultivation as well. An alternative that has further improved on teh perfromance of the vitro process is the use of a double-phase culture system (semi-solid medium with a layer of liquid medium on the top), in which shooting and rooting are performed simultaneously. Other approaches include the sue of bioreactors, which improve the physiological state of the explants. Such systems are commercailly available, such as automated tmporary immersion (RITA® and Plantform ™ bioractors, the rocker system as well as others. (Mitsis, “An Alternative in vitro Propagation Protocol of Cannabis sativa L. (Cannabaceae) presenting efficient rooting, for commerical production” Plants, 2022, 11(10): 1333).

(Mitsis, “An Alternative in vitro Propagation Protocol of Cannabis sativa L. (Cannabaceae) presenting efficient rooting, for commerical production” Plants, 2022, 11(10): 1333) discloses an in vitro propagation protocol in vitro cutting disinfecstation, culture establishment, and root induction, as well as acclimimatization of the in vitro-propagated plantlets using pet-based sponges as a substrate, impregnated in liquid medium. Root initiation of in vitro-propagated cuttings was commenced during the third week fo culture, depending on the rooting treatment. Cuttings were excised from selected healthy young medical C. sativa L. plants at the vegetative grwoth stage. Two varieties, a high-cannabidiol plant variety (H_CBD) and a high-cannabigerol plant variety (H_CBG), of C. sativa L. (Cannabaceae) were included in the study. The cuttings’ donor plants were grown in a green house. Elite (based on chemical profile) female plants were used in the xperiments. Motehr plants were selected ruing a previous research study and maintained at the vegetative stage for a photoperiod of 18 h. All plants were kept indoors, under controlled envornmental conditions at 27C ± 2 C. 

Supply/Type of Light Used:

To determine the appropriate lighting (and the best lamp to use), the specific needs of the plant must be considered, as well as the room size and ventilation. To arrange optimal lighting, the lighting present in the plant’s natural environment needs to be imitated. For example vegetables grow best in full sunlight, which means in practice that as much light as possible must be supplied to grow cannabis indoors (high intensity discharge (HID) lights such as high pressure sodium (HPS) and metal halide (MH) are preferred. Fluorescent lamps can also be used). Incandescence and mercury vapor lighting are not used in cannabis cultivation. (US 20120311744)

In addition, plants also require both dark and light (“photo”-) periods. As such, lights need to be timed to switch them on and off at set intervals. The optimum photo/dark-periods is specific depending on each plant (some prefer long days and short nights and others preferring the opposite, or something in between). Most plants will grow under most light spectra, yet always prefer a full spectrum light (HPS). However, certain plants (as cannabis) can be grown successfully under both types of light. MH is used for 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 as cannabis the amount of working substances as THC) produced by the plant. High pressure sodium lamps trigger a greater flowering response in the plant and are thus used for the second (or reproductive) phase of the growth. If high pressure sodium lamps are used for the vegetative phase, plants will usually grow slightly more quickly, but will also have longer inter nodes, and may be taller. (US 20120311744)

According to the inverse square law, the intensity of light radiating from a point source (in this case a bulb) is inversely proportional to the square of the distance from the source. So if an object is twice as far away, it receives only 1/4 the light. This is a serious hurdle for indoor marijuana growers, and many techniques are employed to use light as efficiently as possible. (US 20120311744)

Reflectors are often used in the lamps to maximize light efficiency. Plants or lights are moved as close together as possible so that they receive equal lighting and that all light coming from the lamps wind up on the plants (rather than partly besides it). Often, the distance between lamp and plant is in the range of 0.6 m (2 ft) with incandescent lamps, to 10 cm (4 in) with other lamps, such as compact, large and high-output fluorescent lamps. Some marijuana cultivators cover the walls of their grow-room with some type of reflective material (often Mylar), or alternatively, white paint to maximize efficiency. (US 20120311744)

One commonly used covering is 6 millimeter (150 .mu.m) PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing in to 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. Mylar sheeting from a grow store is very effective when it lines grow room walls, along with Astrofoil (which also reflects heat), and Foylon (a foil-laminated, reinforced fabric). (US 20120311744)

LED: Recent advancements in LED technology have allowed for diodes that emit enough energy for cannabis cultivation. One major short coming of LED’s in the past has been a lack of intensity. Higher wattage chips are required to produce enough luminous efficiency to produce larger, denser yields. As with using a 400 w HPS vs. a 1000 w HPS, intensity has everything to do with yield. The same applies to LEDs however, it is not as simple as measuring watts because better quality chips can produce more light with less watts than cheap chips running at lower watts.LED grow lights are still considered an experimental technology in cannabis cultivation. The market remains flooded with cheap quality LED lights that do not produce yields comparable to what growers are accustomed to. Many companies are using single watt LED chips, which have notoriously produced low yields and wispy results. Growers should look for lights with 6 watt chips. When considering purchasing LED grow lights, one should carefully examine both the spectrum and the intensity of the light. The advantages of LEDs, low heat output, long life span, and simpler environmental control, coupled with the ever increasing quality of the technology ensure that they can potentially mark a significant transformation in the cultivation of cannabis. NASA has experimented with LED panel light sources on plant growth.(US 20120311744)

HPS bulb: has most of the light spectrum in the “orange” range, with almost no `blue` and very little `red.` For this reason, it is poor in the 430-460 nm, and poor in the 680-700 nm. Luckily, the light is so powerful that the spill-over at these frequencies is still sufficient to do a good job. The principal shortcoming of the HPS lamp turned it into an advantage for LEDs. LED lights allow one to focus intensity in the high PAR absorption range of the light spectrum. New models of LED grow lights incorporate multiple types of chips that cover the whole range of red light, blue light, and now full spectrum light. (US 20120311744)