All You Need To Know About Cannabis Seeds, the explosive growth of seed breeders and legal seed sales in the Netherlands, the United Kingdom, Canada, France, Switzerland, Spain, etc., has given way to more strains of cannabis than ever before.
All You Need To Know About Cannabis Seeds
Most popular strains of cannabis are a combination of two or more of the following: C sativa, C indica, C ruderalis, and C. afghanica. But there are also many seeds with the genes from just one of the above.
These strains of cannabis are bred to grow best indoors. Others grow best in greenhouses, and still others outdoors in specific climates. See Chapter Seventeen, “Breeding,” for information about hybrid seeds including F1,F2, F3, etc., hybrids.
A seed contains all the genetic characteristics of a plant. Seeds are the result of sexual propagation and contain genes from each parent, male and female. Some plants, known as hermaphrodites, bear both male and female flowers on the same plant.
The genes within a seed dictate a plant’s size; disease and pest resistance; root, stem, leaf, and flower production; cannabinoid levels; and many other traits. The genetic makeup of a seed is the single most important factor dictating how well a plant will grow under artificial light or natural sunlight and the levels of cannabinoids it will produce.
Strong, healthy parents and proper care yield strong seeds that germinate well. Strong seeds produce healthy plants and heavy harvests. Seeds stored too long will germinate slowly and have a high rate of failure. Vigorous seeds initiate growth within seven days or sooner.
Seeds that take longer than a month to germinate could always be slow and produce less. However, some seeds take longer to germinate even under the best conditions.
The cask, or outer protective shell, on some seeds never properly seal, which allows moisture and air to penetrate. It also causes hormone concentrations to dissipate and make seeds less viable. Permeable seeds signal diseases and pests to move in. Such seeds are immature, white, fragile, and crush easily with slight pressure between finger and thumb. These are weak seeds and do not have enough strength to grow well.
Typically, a grower who acquires a bag of ten quality seeds from a reputable seed company germinates them all at once. Once germinated, the seeds are carefully planted and grown to adulthood. By and large, of the ten seeds, some will be male, some will be weak and grow poorly, and two or three seeds will grow into strong, super females. Of these “super” females, one will be more robust and potent than her siblings. This super female is selected to be the mother of countless super clones.
A simple picture of a seed reveals an embryo containing the genes and a supply of food wrapped in a protective outer coating. Mature seeds that are hard, beige to dark brown, and spotted or mottled have the highest germination rate. Soft, pale, or green seeds are usually immature and should be avoided. Immature seeds germinate poorly and often produce sickly plants. Fresh, dry, mature seeds less than a year old sprout quickly and grow robust plants.
All You Need To Know About Cannabis Seeds
Cannabis seeds need only water, heat, and air to germinate. They do not need extra hormones to germinate. Seeds sprout without light in a wide range of temperatures. Properly nurtured seeds germinate in two to seven days, in temperatures from 70-90F (21-32C).
Temperatures above 90F (32C) impair germination. At germination, the outside protective shell of the seed splits, and a tiny, white sprout (radicle) pops out. This sprout is the root or taproot. Cotyledon, or seed leaves, emerge from within the shell as they push upward in search of light.
Timeline for germinating seeds
At 55-72 hours:
- Water is absorbed
Root tip (radicle) is visible
At 10-14 days:
- First roots become visible
At 21-30 days:
- At least half of seeds are rooted by day 21. Seeds not rooted by day 30 will probably grow slowly
Once seeds are rooted, cell growth accelerates; stem, foliage, and roots develop quickly. Seedlings develop into full vegetative growth within four to six weeks of germination.
Seeds are prompted to germinate by:
- Air (oxygen)
Soaking seeds in water allows moisture to penetrate the protective seed shell within minutes. Once inside, moisture continues to wick in to activate the dormant hormones. In a few days, hormones activate and send enough hormone signals to produce a radicle.
The radicle emerges upward to bring a new plant into the world. Once a seed receives moisture, there must be a constant stream of moisture to transport nutrients, hormones, and water in order to carry on life processes. Letting germinated seeds suffer moisture stress now will stunt seedling growth.
Temperature for Cannabis seeds
Cannabis seeds grow best at 78F (25C).Low temperatures delay germination. High temperatures upset seed chemistry causing poor germination. Seeds germinate best under the native conditions where they were grown.Once germinated, move seedlings to a slightly cooler growing area, and increase light levels. Avoid high temperatures and low light levels, which cause lanky growth.
Seeds need air to germinate. Moist, soggy growing mediums will cut off oxygen supplies and the seed will literally drown. Planting seeds too deeply also cause poor germination. Seedlings do not have enough stored energy to force through too much soil before sprouting. Plant seeds twice as deep as the width of the seed. For example, plant a 0.125-inch (0.3 mm) seed 0.25-inch (6 mm) deep.
Household water contains enough dissolved solids (food) to nourish seeds through their first few weeks of life. Although seeds need only 30-50 ppm of nitrates before they germinate, any more will disrupt internal chemistry. Some growers prefer to use distilled water that contains virtually no dissolved solids to germinate seeds. In fact, a high concentration of dissolved solids (salts) in the water will actually pull moisture out of the seed!
Start feeding two to four weeks after seedlings have sprouted. Some growers wait until leaves yellow to begin feeding. Use a mild quarter-strength solution. If yellowing persists, give seedlings a little more fertilizer.
Some seeds have a very hard outer shell, testa, and must be scarified to allow water to penetrate. To scarify, line a matchbox with a piece of fine-grain sandpaper or emery board. Put the seeds in the matchbox and shake for about 30 seconds. Remove the seeds, and make sure they have been scuffed a bit. Just a little scuffing will allow water to enter and set germination in motion.
Two Popular Germination Techniques:
- One: Pre-soaking in water
Soak seeds overnight in a glass of water. Make sure seeds get good and wet so growth is activated. Do not let seeds soak more than 24 hours, or they might get too wet, suffer oxygen deprivation, and rot. Once soaked, seeds are ready to be placed between moist paper towels to sprout or be planted in a root cube or fine, light soilless mix.
In a warm location (70-90¬∞F, [21-32¬∞C]), place seeds in a moist paper towel or cheesecloth, making sure they are in darkness. Set the moist cloth or paper towel in a vertical position (so tap root grows down) on a grate (for drainage) on a dinner plate.
Water the cloth daily, and keep it moist. Let excess water drain away freely. The cloth will retain enough moisture to germinate the seed in a few days. The seed contains an adequate food supply for germination. Prevent fungal attacks by watering with a mild two-percent bleach or fungicide solution.
Once seeds have sprouted and the white sprout is visible, carefully pick up the fragile sprouts (with tweezers) and plant them. Take care not to expose the tender rootlet to prolonged intense light or air. Cover the germinated seed with 0.25-0.5-inch (1-2 cm) of fine planting medium with the white root tip pointing down.
- Two: Direct seed
One of the problems with rockwool can be that the seeds heave out before germinating. This is why it is best to germinate seeds before putting them into the rockwool substrate.
Once seeds have sprouted and the white sprout is visible, carefully pick up the fragile sprouts (with tweezers) and plant them in a pre-drilled hole in the rockwool with the white root tip pointing down. Take care not to expose the tender rootlet to prolonged intense light or air. Cover the germinated seed with one-quarter to one-half inch of moist rockwool. Keep the rockwool evenly moist. Once the taproot sprouts, small fuzzy feeder roots will grow in 12-14 days.
Water penetrates the outer protective shell, continues to wick in and activates dormant hormones that induce germination. Once a seed receives moisture, there must be a constant stream of moisture to transport nutrients, hormones, and water to carry on life processes. Letting germinated seed suffer moisture stress now will stunt or stop seedling growth. The black tip of the root tells me this is what has happened.
Soggy growing mediums cut oxygen supplies and cause seeds to drown. Planting seeds too deeply causes poor germination.
Seedlings do not have enough stored energy to force through too much soil before sprouting. Plant seeds twice as deep as the width of the seed. For example, plant an eighth-inch seed one-quarter inch deep.
Seeds do not need any extra hormones to germinate. Household water contains enough dissolved solids, food, to nourish seeds through their first few weeks of life. Supplemental nutrients will disrupt internal chemistry. Some growers prefer to use distilled water which contains virtually no dissolved solids to germinate seeds.
Sow (direct seed) or move the sprout into a shallow planter, small seed pot, peat pellet, or rooting cube. Keep the planting medium evenly moist. Use a spoon to contain the root ball when transplanting from a shallow planter. Peat pellets or root cubes may be transplanted in two to three weeks or when the roots show through the sides. Feed with a dilute, quarter-strength fertilizer solution.
Construct a moisture tent over the seedling container to help retain even grow-medium moisture. To build, place a baggie or piece of cellophane over the seeded soil. The cover will keep the humidity and temperature elevated. Seeds usually need only one initial watering when under a humidity tent. Remove the cover as soon as the first sprout appears above ground. Leaving the tent on after seeds sprout through soil will lead to damping-off and other problems.
Place planted seeds under an HID lamp to add dry heat while germinating. The heat dries soil, which requires more frequent watering. Place a heating pad or soil heating cables below growing medium to expedite germination. Marijuana seeds germinate and sprout quickest when the soil temperature is between 78-80¬∞F (24-27.5¬∞C) and the air temperature is 72-74F (22-23C). But stems
will stretch between internodes if temperatures exceed 85F (29C) for long.
Over-watering and under-watering are the biggest obstacles most growers face when germinating seeds and growing seedlings. Keep the soil uniformly moist, not waterlogged. Do not let the growing medium surface dry for long. Keep it evenly moist. Setting root cubes or planting flats up on a grate allows good drainage.
A shallow flat or planter with a heat pad underneath may require daily watering, while a deep, one-gallon pot will need watering every three days or more. A properly watered flat of rock-wool cubes needs water every three to five days when sprouting seeds. When the surface is dry (0.25-inch [7 mm] deep) it is time to water. Remember, there are few roots to absorb the water early in life, and they are very delicate.
Grow More Female Plants from Seed
Environmental factors start influencing sex the moment the seedling has three pairs of true leaves (not counting cotyledons). Environmental factors that influence sex determination of cannabis include but are not limited to:
Increasing the level of nitrogen makes more female plants. Lower the nitrogen level to create more male plants. Increase the level of potassium to increase male tendencies; lowering the potassium level encourages female plants. A higher nitrogen level and a lower potassium level for the first two weeks increases females.
Low temperatures increase the number of female plants. Warm temperatures make more male plants. High humidity increases the number of female plants. Low humidity increases male plants.Low growing medium moisture increases males. More blue light increases the number of female plants. More red light increases male tendencies. Fewer hours of daylight (e.g. 14 hours) increases the number of females. Longer days (e.g. 18 hours) make more male plants.
Stress: any environmental stress tends to yield more male plants when growing from seed.
When seed sprouts, the white tap root emerges. Soon afterward, the cotyledon, also known as seed or seedling leaf, appears. The seed leaves spread out as the stem elongates. Within a few days, the first true leaves appear, and the little plant is now officially a seedling.
This growth stage lasts for three to six weeks. During seedling growth, a root system grows rapidly while green above ground growth is slow. Water and heat are critical at this point of development. The new, fragile root system is very small and requires a small but constant supply of water and warmth.
Too much water will drown roots, often leading to root rot and damping-off. Lack of water will cause the infant root system to dry up. As the seedlings mature, some will grow faster, stronger, and appear healthy in general. A little heat now will help nurture small seedlings to a strong start.
Other seeds will sprout slowly and be weak and leggy. Cull sickly, weak plants, and focus attention on the remaining strong survivors. Seedlings should be big enough to thin out by the third to fifth week of growth. Thinning out seedlings is very difficult for growers who pay $300 dollars for a few seeds!
Seedlings need at least 16 hours of light daily. They require less intense light now and grow well under fluorescent tubes for the first two to three weeks. Compact fluorescent and HID light can also be used. The compact fluorescent should be 12-18 inches (30-45 cm) and the HID 3-4 feet (90-120 cm) above seedlings for best growth.The seedling stage is over when rapid foliage growth starts. Rapid growth above ground is the beginning of the vegetative growth stage. Plants need more room to grow; transplanting into a larger container hastens development.
Store seeds in a cool, dark, dry place. Make sure to label containers! Some seeds will remain viable for five years or longer when stored properly. When 50 percent of the stored seeds do not germinate, the average storage life is over. But seeds a year old or older often take longer to sprout and have a lower rate of germination.
Seed hormones-ABA, cytokinins, and gibberellins-are primed to respond to moisture, which is the first signal to germinate. Prevent moisture from signaling seeds to germinate by keeping them dry. Small amounts of moisture in the form of condensation can give seeds a false start on germination and cause them to expend all their stored energy.
Avoid moisture levels above five percent to ensure viable seed. Moisture levels above five percent will cause germination levels to decrease rapidly. Seal seed in an airtight container, and place silicon crystal packages in the container to absorb excess moisture.
Cannabis seeds need enough moisture to initiate this process within 48 hours.
Dry seeds are temperature-sensitive; they can be disinfected with a short application of heat. Low temperatures slow internal seed activity so are best for preserving seeds. You can use super-cold liquid nitrogen and cryogenics to store seeds for a long time.
Air, once it enters the outer seed shell, signals seeds to germinate. Viable seeds are preserved longer when vacuum-packed to remove all oxygen.
Seeds with a thin, outer protective shell never truly go dormant, because moisture and air are always present within. This moisture and air cause hormone levels to slowly dissipate. Such seeds do not store well for a long time.
Cannabis Seed Pests
Seed pests become active when there is more than ten percent moisture content. When the growing medium contains more than fifteen percent moisture, fungi become active. Excess fertilizer slows seedling growth and promotes fungus attacks.
Temperatures from 68-85¬∞F (20-30¬∞C) promote Pythium (damping-off) and rhixocto-nia fungi. Cannabis seeds grow best at 78¬∞F (25¬∞C). Most fungi reproduce fastest in a temperature range of 68-86T (20-30¬∞C).
Keep a wary eye on problems. Nutrient overdose burns leaf tips and fringes, which can look like damping-off to the untrained eye. Do not fertilize. Applying a fungicide now will make the problem worse.