It's written by Jorge Cervantes, one of the premier cannabis cultivation gurus.
I thought the information was way to good to not post it, especially because it dispels a lot of myths, misconceptions, and useless practices when starting off your seeds. This is great for beginners and novices alike.
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 70-90°F (21-32°C). Temperatures above 90°F (32°C) 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. Seeds are prompted to germinate by water, temperature, and air (oxygen).
Soak seeds in moist paper towel.
Photo by Jorge Cervantes. Water
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.
Cannabis seeds grow best at 78°F (25°C). 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 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 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.
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, if at all.
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.
This germinated seedling was allowed to dry out for a little more than an hour, and the tip of the root shrivelled, which caused the plant to have a very slow start in life.
Photo by Jorge Cervantes
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.
Plant seeds twice as deep as the seed is wide.
Diagram courtesy of Jorge Cervantes 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, 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.
To quick start your seeds, place a small emery board inside a matchbox along with seeds. Close the match box with the seeds and emery board inside. Shake the box for about 30 seconds to rough up and scuff the seeds, so water can penetrate the outer shell. Soak seeds in water overnight to germinate before planting. Place seeds between leaves of a paper towel on a plate to germinate. Add water to moisten the paper towel. Tip plate to drain off excess moisture.
Jiffy pellets expand when water is added. They make excellent pop-up pots to grow seedlings. They are also very easy to transplant.
Two — Direct seed into medium
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. Seeds set inside rockwool
blocks often heave up and out. Germinate seeds before planting to avoid this common problem.
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 under a humidity tent usually need only one initial watering. Remove the cover as soon as the first sprout breaks ground. Leaving the tent on after seeds sprout through soil will lead to damping-off and other problems.
Photo by Jorge Cervante
Place planted seeds under an HID lamp to add dry heat while germinating. The heat dries soil, which requires more frequent watering. Place a heat pad or soil heating cables below growing medium to expedite germination. Cannabis seeds germinate and sprout quickest when the soil temperature is between 78-80°F (24-27.5°C) and the air temperature is 72-74°F (22-23°C). But stems will stretch between internodes if temperatures exceed 85°F (29°C) 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 rockwool 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.
Photo by Jorge Cervante Grow More Female Plants from Seed
Environmental factors start influencing sex the moment the seedling has three pairs of true leaves (not counting cotyledon). 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.