GETTING STARTED
Indoor
The lights are in position. The growing unit, hydroponic system, or planting containers are in place. Fans are installed in the space as appropriate to provide air circulation. A CO2 enrichment or ventilation system is set up to provide a continuous supply during the lit period.
Temperature and humidity are controlled with sensors and automatic systems using air conditioners and dehumidifiers in either a closed-loop system or a ventilation system using filtered outside air.
The nutrient solution is monitored by measuring either parts per million (ppm), electrical conductivity (EC), or total dissolved solids (TDS). (See Water and Nutrients & Fertilizers.) A pH meter or test kit is used to measure pH. A surface temperature thermometer and a light meter are also useful.
Greenhouses
The greenhouse is in working order. Vents, openings, evaporative coolers, or other cooling methods are operable using an automatic system controlled by a thermostat and humidistat. If soil is being used, the planting beds or containers have nutrients and soil amendments mixed in. If a hydroponics unit is being used, it has been set up and is ready to plant.
Any supplemental lighting is in place to increase the intensity of the light during low-light periods and/or, when needed, to extend day length during the shorter days of the year. Blackout curtains are used to shorten the day length inside the greenhouse and trigger flowering during the longer days of summer.
Outdoors
The ground, planting holes, or raised beds are prepared and ready to be planted. In dry areas where there is little rainfall during the summer, irrigation is required to grow crops, so the water is sourced and ready to flow. If the plants are to be forced to flower early, the frames and blackout curtains have been installed.
Everything is set.
It’s time to give this garden life!
Seeds or Clones?
There are two ways to start a garden: using either seeds or clones.
Seeds
Seeds have several advantages. Only plants grown from seed develop a taproot. The taproot is the underground equivalent of the main stem. The taproot on plants grown from seed is an extension of the stem, so it anchors the plant and holds the canopy securely. It grows straight down with lateral roots branching out along its length, providing the plant with a network that occupies a larger three-dimensional area. A deep taproot can reach the water table or moist layers of penetrable subsoil. The taproot and main stem form a single column, so water and nutrients are drawn easily up to the plant canopy. The result is that there are more roots in several layers of soil that can obtain more water and nutrients to support the plant’s growth.
The depth and vigor of a root system are also essential for the stress tolerance and resilience required to optimize sun-grown cannabis.
Seeds are less likely to carry and spread pests and pathogens, while clones can transfer them readily.
Seeds are the product of sexual reproduction, so they inherit genetic characteristics from both parents. Plants from the same seed stock exhibit different characteristics due to genetic variation, so growers can choose the best plant, or the one they like best, and reproduce it using cloning. Growing from seed is more adventurous, because there is no way to know exactly how the plants will turn out. (See Basic Breeding.)
Seeds are very portable and easy to store for long periods of time.
Seeds of many varieties are readily available in shops, dispensaries, by mail, and over the internet. It is easy to verify the variety when it comes from a seed company. Investigate and select carefully. First investigate the company and then read reviews of the selections. How long has the company been in business, and what is its reputation? Has the cultivar won awards, and in what categories? Reach out to the vendors if there are questions. Many times their response influences purchasing decisions.
Seeds have several disadvantages. Cannabis has separate male and female plants. Unless they are used for breeding or hemp for seeds, males are of no use and will become pollinators that endanger the potency and yield of seedless, cannabinoid-rich, female flowers.
Usually, about half the seeds produce males, which must be detected and removed. This can be an arduous task, and the consequence of missing one can be seeded buds throughout the garden.
Seeds take longer to germinate, grow, and be ready to flower because rooted clones are already biologically mature, so they are 15-20 days ahead on root development.
Plants from seeds don’t exactly reproduce their parents’ traits. Seeds from a finished bud will not grow to be exactly the same as their mother, though their morphology may be a close approximation. This is just how different siblings from the same parents are genetically and physically unique from one another, unless they are identical.
Because roughly half of the plants will be discarded once they are sexed, growing from seeds is more likely to result in fewer plants than anticipated.
Feminized Seeds
Feminized seeds have been bred to produce only female plants. They are the solution to the problem of sexing males, since virtually all the feminized seeds will grow to be female plants.
Feminized seeds are created by treating a flowering female plant with a chemical catalyst, such as colloidal silver, silver nitrate, or preferably silver thiosulfate. This induces female plants to grow pollen-producing male flowers. Because the mother plant has only female chromosomes, it contributes only female genetics to any seeds produced. The result is that virtually all the plants will be female. (See Basic Breeding: Feminizing Seeds.)
Clones
Cloning is the asexual reproduction of another plant. No pollen or seed is needed. Rather than being a genetic mix, a clone is the exact genetic reproduction of the plant from which it was taken. There are other methods of asexual reproduction, including tissue culture. (See Appendix A: Cloning and Appendix B: Tissue Culture.)
The Mondi Mini Greenhouse Propagation Kit includes the Black and White Premium Tray, seven inch (18 cm) Mini Greenhouse Dome with easy vents, and an attachable thermo-hygrometer. The patented Black and White Premium Tray is designed to be strong while using less plastic in order to minimize the environmental impact. Its interior white plastic increases light reflectivity, while the black base prevents light penetration to the root zone, reducing the chance of root disease. It is easy to clean and very durable. The seven inch (18 cm) Mini Greenhouse Dome is made from premium proprietary plastic that does not off-gas and is safe for food production. It is designed to tightly control temperature and humidity through adjustable vents. The patented thermo-hygrometer has a unique mounting, allowing easy access to accurate measurements inside the controlled environment.
There are many benefits to working with clones. Because they are taken from female plants, they are also female with no males or hermaphrodites to mess with the buds. Clones get the grower past the germination “hump” seeds present. Seeds take 15-20 days to catch up to a rooted clone, which is ready to be transplanted and start vigorous growth.
Commercial clones come from stock that has already proved itself vigorous and potent. Rather than having to select the best from a group of plants grown from seeds, the arduous selection process has already been done.
Clones from a single mother are genetically identical because they are the result of asexual reproduction. Growing a uniform crop is easier than growing different varieties or even different plants of a single variety.
Clones make it easier to limit the number of plants in the garden because they can be obtained or cut to replace plants as they are placed into flowering.
There are disadvantages of clones. Clones are only available commercially in regions where cannabis is permitted for home cultivation. Not all varieties are always available, even when they are legal. Clones can carry diseases and pests that infect the whole garden. Clones from friends are more likely to be infected than professionally grown clones.
There are major disadvantages starting from clones for outdoor growers. Clones do not grow as vigorously as seed-grown plants, especially outdoors, because clones do not grow a taproot, only secondary roots from the stem, and therefore do not develop as deep or vigorous of a root system as plants grown from seed. When grown in the ground or large planting beds, they generally do. Clone plants have a single layer of lateral roots. The stem ends close to the soil line, where it was cut. This doesn’t provide as much support as a plant with a taproot.
Subsequently, some of their growth is lateral rather than downward, which may not provide access to optimal moisture found in deeper soils and limits the plants’ resiliency during stressful weather conditions.
This doesn’t affect plants grown inside in the same way because the plants don’t grow as large and the taproot isn’t as important in a container environment.
Selecting Seeds
by Professor P
Selecting viable seeds isn’t difficult and can be done mostly by a brief visual inspection. Is the seed fully formed without indentations, cracks, holes, or have a white/green tint? Do the seeds sink or float? Seeds that continue to float after 12 hours are possibly not viable, but seeds that sink are more suitable candidates for germination and generally have a high percentage of success. Green seeds, undeveloped seeds, and cracked shells are highly unlikely to sprout, but some may miraculously do so at a much lower percentage.
Seed color is another indicator. Although darker seeds tend to be more mature, a few cultivars produce fully mature light-colored seeds. This is the result of the plant’s adaptation to its environment.
After a visual examination, a further inspection is performed by squeezing the seed firmly. If it crushes with minimal pressure, it’s a dud. If it doesn’t crush with continued pressure, it is viable no matter its color.
Photo: Professor P of Dynasty Genetics
Overripe seeds present another problem. The embryo bursts the seed shell open, creating a split along the seed hull. Split seeds may be viable for a short amount of time before the embryo dries out and dies.
Viability of aged seeds is affected by storage conditions. For long-term storage, they should be kept frozen until shortly before use. To extend their life, keep them refrigerated in a sealed container. Seeds stored at room temperature start losing vitality after about a year. Some may survive up to three years.
Shells of poorly handled seeds often have small blue specks. A quick dip in 3% hydrogen peroxide eliminates the mold, fungi, and some bacteria. After the hydrogen peroxide dip, soak in a diluted microbial solution such as Bioharmonic Tonic or Trichoderma harzianum (URB), which promote plant biology.
Healthy, fresh cannabis seeds do not require scarification to naturally germinate, but it increases the germination rate of challenged seed. It is done with a few strokes of the seed against a nail file or sandpaper. Scraping away part of the shell assists in introducing water into the seeds, which signals them to germinate.
Cold “stratification” is sometimes used for germination of older seeds from cold climate cultivars. Although cold climate seeds readily germinate soon after dropping from a plant in autumn, the embryo may be stimulated after experiencing a cold spell, depending on the genetics. A visit to the freezer for 24-48 hours is suitable. Again, this is not necessary for most cannabis seeds to properly germinate, but some stubborn seeds may need a little extra nudge. Sometimes feral varieties from cold climates germinate sporadically and require several freezes and thaws.
There are many ways to navigate the realm of seed viability, but it all starts with proper storage. To store seeds properly, three environmental factors must be addressed: light, humidity, and temperature. Cannabis seeds retain their viability longest when they are stored in cool, dark, and fairly dry conditions. Seeds stored in a jar in a dark space at room temperature start to lose viability after two years. They may remain viable for four years or more in a refrigerator with low humidity. Seeds packaged properly can remain in a freezer for an extended period. The biggest threat to seed viability is high humidity and warmth. Humidity between 20-30% and temperature of about 41-45°F (5-7°C) is ideal for most situations.
Starting Seeds
Fresh seeds are usually viable, with high germination rates. Seeds more than two or three years old may not germinate as well. Older seeds may have a higher percentage of weak plants, and slower germinating seeds are more prone to attack from molds and bacteria.
Bioharmonic Tonic is a bioharmonically active microbial mix derived from all-natural ingredients. A fermentation and enzymatic process is used with a special blend of Amazonian herbs and gemstone harmonics. This easy-to-use odorless liquid is a dynamic mix of biostimulants ready to invigorate growth. Professor P has used it over several tests and found that it increases germination on older seeds and accelerates early growth.
Intact, dark brown, or gray seeds are most likely to germinate. Whitish, light tan, or cracked seeds are usually not viable. Most grow books suggest selecting the largest seeds in a batch for planting, but the size of the seed is genetically as well as environmentally determined and does not necessarily relate to its germination potential.
Cannabis seeds germinate best in a warm room temperature range of 70-80°F (21-26°C). At lower temperatures, germination proceeds slowly, and seeds are subject to attack by fungi and bacteria.
There are multiple methods of germinating seeds.
Planting in Place
The easiest method of germination is by planting directly in the ground or planting medium, in small cups or containers using soil or planting mix, peat pellets, rockwool cubes, or other germination media.
Pasteurized or sterile planting media or substrates such as rockwool and most indoor planting mixes are excellent for seed starting. Keep the water pathogen-free by using a 0.5% solution of hydrogen peroxide or protect the roots using compost tea or root-protecting organisms such as mycorrhizae. Do not use the hydrogen peroxide concurrently with the mycorrhizae, or they will be killed.
Paper cups (not plastic) are convenient germinating containers, but they must be removed or well scored before planting. Lightweight horticultural cups made from peat moss, straw, rice, paper, or other natural materials are ideal containers for germinating plants that are to be transplanted. They can be placed directly in the ground or into a larger container without disturbing the roots.
(1) The seeds have germinated. Photo: Picture Fotografie (2-3) The stem is emerging. Photo: (2) Phil Sullivan / Team Terpene (3) Picture Fotografie (4) The cotyledons are opening. Photo: Phil Sullivan / Team Terpene (5) The first true leaves have appeared. Photo: Phil Sullivan / Team Terpene (6) Seedling are labeled and will carry IDs until harvest. Photo: GreenSourceGardens
Germinating in rockwool blocks, Oasis cubes, or bonded peat cubes also avoids having to remove rooted plants from the container. Starter sheets fit in standard 10 x 20 inch (25 x 50 cm) horticultural trays and are divided into either 30, 50, or 72 cubes. Seedlings should be attached to growing blocks, planting mix, or soil soon after germination. The 30s can usually remain 15-20 days, the 50s 10-15 days, and the 72s about 7-10 days.
Four inch (10 cm) diameter cubes can hold the plants for two weeks to a month without inhibiting growth. Six inch (15 cm) containers can keep plants comfortable for four weeks or more, and even through flowering for small plants.
Germination Techniques
There are many methods of germinating seeds. Germinating in a wet paper towel is among the most popular.
Moisten the paper towel or cloth with water until it is almost saturated. Place the seeds on the towel and fold it over. Put the folded towel or cloth on a bowl or plate and cover it with plastic wrap. Check the seeds once or twice a day for signs of germination. When it is apparent that the taproot is emerging, place the seed in the prepared sterile or pasteurized growing media at a depth of about a quarter of an inch (5 mm). Be careful not to injure the emerging root when planting. Keep it moist.
Seeds can be germinated in place in rockwool blocks or cubes, peat plugs, or other media starts. These are very convenient to use because they come ready to plant. Place the seed about three eighths of an inch (9.5 mm) deep in the block or cube and keep the seeds and seedlings moist.
To keep the environment disease-free, treat the water with a 0.5% solution of hydrogen peroxide (H2O2). Drugstore hydrogen peroxide is 3%, so mix one part hydrogen peroxide for every five parts water to create a 0.5% solution.
Compost tea also protects germinating seeds and seedlings because it contains living microorganisms that may outcompete pathogens and aid root growth. Before adding it, make sure to rinse out the H2O2 because it will kill microorganisms.
Whether seeds are germinating indoors or outside, the planting medium must be kept moist during the entire period. Seeds dry out quickly during this process, and dry medium results in dead seeds. If possible, place a cover or clear plastic film over them. The sun can dry the surface of the soil very quickly, so it is best to plant outdoors when the soil will remain moist for a few days. Otherwise, it may be more successful to germinate indoors or in the shade outdoors and then transplant. This is more of a problem in the late spring and summer, when the light becomes more intense and high temperatures increase evaporation.
IHORT Quick Start® plugs are made from a custom proprietary blend of peat moss, coco coir, and biochar to create the ideal propagation conditions. They are expertly designed for the optimum amount of moisture and aeration and come predrilled for enhanced stem-to-media contact. All plugs come pH balanced ready to use right out of the box. IHORT plugs promote more fibrous root growth to aid in water and nutrient uptake and increase the amount of branches per plant and stem caliper, providing more tips on mother plants or increasing yield.
Seeds usually germinate in 3 to 10 days. Germination time is affected by media temperature as well as the seed’s age and health. The best temperature range for germination is in the high 70s Fahrenheit (mid-20s Celsius). At lower temperatures germination is prolonged.
The elongated stems of these seedlings are the result of too dim or too little light, or too high a temperature.
First the root emerges. Shortly after, the stem emerges and orients itself perpendicular to gravity. Folded on top of the stem, a pair of embryonic leaves called cotyledons unfold and begin to supply the plant with the sugars it needs for growth and respiration. Cotyledons are rounded single blades and look nothing like mature cannabis leaves.
As soon as plants germinate, they require light. If the light is not intense enough, the stem stretches, reaching for it. If the lighting creates too much heat, the young seedling’s leaves may burn. This could also dry out the planting medium, adding to the seedling’s stress. Depending on the intensity of the lighting fixture, the distance between the light and newly germinated seedlings must be adjusted.
Plants can be started under LED panels, kept at least 24 inches (50 cm) above the surface of the grow media. Seeds can be started under either standard T-8 or T-5 fluorescents or under CFLs. Place fluorescents about 2 to 12 inches (5-30 cm) above the canopy. Space high-output T-5s and high-watt CFLs about a foot (30 cm) above the plants. The plants can also be started under metal halide (MH) or high pressure sodium (HPS) high-intensity discharge lamps or place the seedlings under them soon after germination.
HPS 600-watt and 1000-watt lamps should be placed about one and a half to three feet (45-90 cm) above the canopy if they are air cooled, and about three to four feet (90-120 cm) if not. Seedlings can be germinated under HPS or MH lamps or can be placed under the lamps shortly after. They can also be moved outside.
Outdoors, the sooner after germination the seedlings are planted, the faster they adapt to the environment. Place them outdoors at the same time of the season as tomatoes and corn are planted. However, depending on the latitude of the garden, the dark period may be too long early in the spring, forcing some varieties to flower prematurely. (See Flowering.)
Seedling Vulnerabilities
Seedlings are at their most vulnerable stage immediately after they germinate. Stem rot, a fungal infection, attacks when the medium is kept too moist or when roots are deprived of oxygen. (See Oxygen.) This can happen when the soil or planting mix is too fine or compressed and holds too much water but not enough oxygen. Seedlings don’t need to be watered as often as media with more porosity. As with germinating, use compost tea or a 0.5% hydrogen peroxide solution to prevent both fungal and bacterial infections in seedlings.
Dry media damage both roots and canopy leaves. The time between first signs of wilt and irreparable damage from dehydration is very short for young plants, which don’t have much of an infrastructure reserve. Dry conditions cause the leaves to wilt as they use the available water in the cells and lose turgidity. If the conditions are caught in time, the plants recover soon after they are irrigated. This situation is time sensitive and should be corrected immediately.
Deer, mice, birds, dogs, and cats have all been noted to have a fondness for cannabis sprouts and young plants. These animal friends should be protected from temptation by installing barriers. Another problem with pets, especially those that live both indoors and outdoors, is that they may carry insects and pests into the indoor garden.
The goal is to grow a stout stem that has the strength to support the canopy. Stem height is mostly determined by a combination of temperature and light intensity. The warmer the temperature, the more light the seedlings require. Stretch is often an indication of too little light for the temperature. The long, slender “pencil neck” shoots subsequently have problems supporting the canopy as it gains weight. This can be resolved either by providing more light or by lowering the temperature. Use fertilizers with relatively low amounts of phosphorus to prevent stretching (Nelson, Song, and Huang 2002).
Minimizing what is referred to as “DIF,” the drop from the daytime temperature high to the nighttime low, can also reduce stem elongation. Although cultivar selection will have the greatest effect on stem length and internodal spacing, limiting diurnal temperature shifts can reduce stretching. Plants are especially sensitive to temperature in the first few hours of daylight. Research shows that using a “morning temperature dip” can achieve the same effect as reducing overall DIF throughout the day and night. This can be achieved by dropping the temperature slightly during the first two to three hours of daylight and then allowing temperatures to reach their normal levels for the rest of the period when lights are on.
To correct stretch that has already occurred, support the seedlings using toothpicks, chopsticks, skewers, or thin bamboo stakes. Once the situation is resolved, the stems will develop more girth.
Too little sun can be a problem for young plants, but so can a withering sun. Seedlings have more problems with this when they are set outside in late spring or during the summer, especially if they have been under lights for a while. To prevent damage from sunlight that is too intense, plants are placed under screening or partial shade when they are first brought outdoors. They are moved to full sun gradually, over five days or so. Plants can also be protected by spraying anti-transpirants on them before they are placed outdoors. These substances place a screen between the leaf and the sun and slow transpiration so the plants won’t wilt.
Seedlings started outdoors or acclimated to direct sunlight will easily adjust to the bright sun. New leaves that grow in the sun will grow longer palisade cells that absorb more light before it reaches the chlorophyll. They position the chlorophyll so it receives less light, protecting it from the more intense environment. In addition, new leaves will not have the sensitivity to UV light that destroys indoor-grown leaves placed outdoors.
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Planting Seedlings & Clones
After cuttings have rooted, the clones grow stems and leaves, starting at the apical meristem, the very top of the growth tip. After seeds germinate, they develop a taproot, and the first true leaves emerge. Seedlings and clones are ready to transplant when they have developed a network of roots and several sets of leaves. In both clones and young plants, the new growth indicates that they are ready to develop under full light indoors. Once placed in the garden, the new growth adjusts to the light intensity.
If the plants are being transplanted into soil or a planting mix, place the entire root ball in the medium just slightly deeper than the root ball’s height so that it is covered with soil, without burying the previously exposed base of the stem. The roots will grow from the root ball in all directions, downward and outward.
Roots concentrate their growth in permeable areas of the growing medium that contain water, nutrients, and oxygen. Whether nutrients are held in the soil or provided using a nutrient-water solution, roots absorb them as simple dissolved salts.
Microorganisms in the planting media digest complex organic nutrients and then release them in a water-soluble form available to the plants. As the plant draws up the nutrients from the water, the planting medium gradually releases more that dissolve in the water. Enriched planting media and soils contain high levels of organic amendments or compost that support seedling growth and will not need supplementation for at least one to two weeks. Some commercial planting media support plants longer. A few are made with time-release formulas that last the entire growing season.
The length of time that a planting mix or soil can support growth depends on several factors. The most important ones are the volume of planting media, nutrient levels of the mix, and growth rate of the plant.
If two plants are growing under identical conditions, except for the container size, the one in the larger container will yield more. Contrary to myths, there is no harm done in growing a plant in a container larger than is required. However, growing plants in containers that are too small slows growth and stunts the plant.
With many cultivars grown in soil or planting mix, the canopy of the plant will typically grow in proportion to the diameter of the roots. A plant with a 10 inch (25 cm) diameter canopy will generally have a root system 6 to 10 inches (15-25 cm) in diameter. The same ratio applies to a plant with a canopy 2 feet (60 cm) in diameter; its root system will typically range from 15-25 inches (38-63 cm).
In contrast, hydroponic plants can grow considerably larger than the size of the root zone because easy access to water and nutrients encourages roots to grow much more densely. As long as the roots have access to water and air, they will colonize the growing medium very densely. The canopies of hydroponically grown plants can cover an area several times the diameter of the container, depending on how well supplied the plant is with its essentials.
Plants probably grow more vigorously without being transplanted from container to container, although using containers that can be transplanted directly minimizes transplanting shock.
The ideal conditions for young seedlings and newly transplanted clones is an environment with ambient temperatures between 72 and 78°F (22 and 25°C). Do not leave the plant containers directly on the floor: cold floor temperatures cool the grow medium and slow plant growth. For the first one to two weeks, use low- to medium-level lighting with an average PPFD of 200-400 µmols, after which the plants can be acclimated to higher levels. Higher-output lights can be used, but should be distanced farther from the canopy. LEDs and other dimmable lamps can be adjusted accordingly and placed closer to the tops of the new transplants.
During early growth, cannabis plants need little special care. The plants adjust to their environment and grow at the fastest pace that limiting factors allow. When provided with optimal conditions, seedlings and clones survive the perils of early growth and, within a matter of weeks, develop into vigorous young plants.
Plant & Container Size
Indoors and outdoors, the size of the container helps determine the size of the plant and its yield. If two identical plants are given the same conditions except for container size, the plant in the larger container will produce more. For this reason, it’s wise to give roots as much room as possible to spread out. Indoors, the container size should be limited only by the space each plant has in the canopy.
Sexing the Young Plants
Sexing is the process of identifying whether the plant is male or female. There are few things more important to careful gardeners than being sure that their crop is protected from unwanted pollination. The plants are sexed as early as possible, even during the seedling stage.
Plants grown from standard seed are either male or female, in a roughly 50-50 ratio. Plants grown using feminized seeds are almost all female, but they still have to be sexed. Unless the grower intends to breed, males have no use in the garden and are detrimental to the crop if their flowers are allowed to open and pollinate the female flowers. Pollination not only creates seeded buds but lowers the effective potency and usable weight. By eliminating males early, fewer resources are spent caring for plants that are to be discarded.
Rather than wait until late in the season to determine sex, there are methods that can be used to sort the plants much sooner. Male plants are likely to be taller and more vigorous than females early in life, so gardeners are often disappointed when their favorite plant turns out to be male; however, plant morphology is a difficult way to figure out the sex.
Two good ways to determine sex are as follows:
- Look at the nodes of the young plant where the leaf petioles and the stem are joined. Sometimes a small, single male or female flower grows at this point. The plant is the same sex as this single flower. Some varieties indicate more than others, so while this method can be helpful, it cannot be used to determine every plant’s sex. Using a magnifier provides a clearer view.
- Early flowering is induced by adjusting the photoperiod. However, forcing the whole plant to flower requires 10 days as it switches to flowering cycle and 10 days to switch back to vegetative growth. Instead, cuttings are taken to determine sex without forcing the whole plant into flowering. Cuttings are placed in a planting mix or a cup with water under a flowering light regimen of 8 hours on, 16 hours off. Cuttings will begin to flower and indicate sex within 7 to 14 days. They will indicate faster if kept in darkness for 3 days before placing them under a reduced light cycle. The cuttings and the plants from which they came have the same sex.
Left: early flowering on a female plant. Right: flowering on a male plant. Photos: Ed Rosenthal
Once the cuttings have indicated, remove the male plants from the garden and destroy them. Sentimentality should play no part in the decision. The indicator cuttings are not worth saving.
(For more on sinsemilla and plant sexing see Flowering.)
Early Plant Growth
In a few weeks, the plants grow a foot (30 cm) or more in height and develop branches typical of their variety. By now, plants from standard seeds should be sexed, leaving only females in the garden. Depending on desired size and plant spacing, they should be transplanted to their final containers or into the ground.
Seedlings and clones that are transplanted into hydroponic units or an unenriched planting mix need fertilizers to supply them with nutrients. Both clones and young plants require fertilizer; see Nutrients & Fertilizers to determine the right ratio of N-P-K to use.
After transplanting, keep the temperature in the low 70s F (low 20s C), if possible. Photosynthesis is limited when the air is kept cool. Since less water and nutrients are required with slower photosynthesis, the roots don’t get stressed and there is less chance of wilting. Keep the CO2 at 500-600 ppm, giving the plants easy access to the gas.
About three days after transplanting, the light intensity is increased and the plants enter rapid vegetative growth. The CO2 is increased to 1200 ppm, and the strength of the water-nutrient solution is raised to midrange. The temperature is raised to 80°F (26-27°C). (See Light to help determine photoperiod.)
If the young plants are destined to be grown outdoors, and they are started under continuous light indoors, they may be shocked into premature flowering when placed outdoors, even in early summer. To prevent this, cut the light regimen to 16-18 hours of light and 6-8 hours of darkness. Indica varieties are especially sensitive.