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From Seed to Seedling—A Comprehensive Guide from Seedsman and Jorge Cervantes

Curious about seeds? Here’s your complete guide.

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From Seed to Seedling—A Comprehensive Guide from Seedsman and Jorge Cervantes
Courtesy of Seedsman

Cannabis seeds are easy to purchase via the internet and are sold at many reputable online sites like Seedsman.com.

Seeds contain the genetic characteristics of cannabis plants. They have genes from both parents, male and female. Some unstable plants have both male and female flowers. They are called “intersex” plants but are often called by the misnomer hermaphrodites.

Cannabis genes dictate plant size, pest and disease resistance, root, stem and leaf size as well as flower and cannabinoid production. Making the proper informed choice when purchasing seeds is the absolute most important aspect of your garden. Make sure to use the expertise of your seedbank to help you choose the right seeds for your environment.

Weak seeds germinate poorly and produce weak plants. The best seeds come from strong resilient parents. Proper seed handling once harvested ensures healthy germination. If seeds are stored too long or that suffer moisture and heat stress will germinate poorly producing weak seedlings. Strong vigorous seeds germinate in a 2-7 days. Seeds that take longer to germinate often grow poorly.

Hybrid vigor describes two stable seeds that have been crossed to form a hybrid. Such seeds are designated as “F1.” Few seed companies produce true F1 hybrids because the parents are not stable. But, if you should happen to acquire actual F1 hybrid seeds they will grow into plants that are about 25% bigger and stronger.

Typically, a grower who acquires 5–15 quality seeds from a reputable seed company germinates them all at once. Once germinated, the seeds are carefully planted and grown to adulthood. Normally some of the seeds will be male, some will grow slowly, and two or three seeds will grow into strong “super” females. Of these super females, one will be more robust and potent. Select this super female to be the clone mother.

Mature viable seeds are hard, light to dark brown, sometimes with irregular-shaped spots and have a 100% germination rate. Green and pale seeds are often immature and germinate poorly growing into weak plants. Look for mature seeds that are dry, hard and less than a year old for best results.

Seeds need only three things to germinate:

  • Moisture
  •  Heat
  • Oxygen
From Seed to Seedling—A Comprehensive Guide from Seedsman and Jorge Cervantes

Courtesy of Seedsman

Moisture

Soak seeds in clean water so that moisture can penetrate the outer shell. Moisture wicks through the protective shell and activates latent hormones. Hormones activate in 24–72 hours and a small white rootlet, called a radicle, starts to grow out of the seed.

A constant supply moisture is critical now. Moisture carries hormones and nutrients to carry on essential survival processes. Use distilled water for best results. Seeds are super fragile at this stage and will suffer immensely if moisture is not consistent.

Heat

The ideal temperature for cannabis seed germination is 78°F (25°C). Temperatures below

70°F (21°C) can cause slow germination while temperatures above 90°F (32°C) cause seeds to germinate poorly. After seeds germinate, plant them in a growing medium and add light. They now need low levels of light and moderate temperatures in the 70°F (21°C) range.

Oxygen

Seeds require oxygen (air) to initiate germination. Soggy over-wet growing mediums stifle the oxygen supply causing seeds to drown. Cannabis seeds that are planted too deeply germinate poorly too.

Cannabis seeds have just enough stored energy to push up through a small amount of soil. They can push through about 0.25-inch (0.6 mm). Super small seeds should be planted a little shallower.

During the first month, it is important to keep a close eye on your seeds. The timeline below suggests what you should be observing during the first few weeks:

  • At 55–72 hours, water is absorbed and the root tip (radicle) is visible.
  • At 10–14 days, the first roots should become visible.
  • At 21–30 days, at least half of the seeds are rooted by this point. 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.
From Seed to Seedling—A Comprehensive Guide from Seedsman and Jorge Cervantes

Courtesy of Seedsman

Seedling Growth

Seeds germinate when given moisture, heat and air. This combination activates hormones inside the seed. Cannabis seeds germinate 24–72 hours after moisture is added. The first signs of progress are the seed’s outer shell splitting and the small white rootlet pops out of the crack.

About 2-7 days after first being given air, heat and moisture, the little white rootlet emerges in full. When planted in fine soil or another growing medium, the rootlet grows downward and two small round-ish (cotyledon) leaves develop above ground, looking for light.

This signals the beginning of the seedling growth stage, which lasts about a month. During the seedling growth stage, the plant develops its initial root system. Most energy is directed toward transforming the single frail rootlet into a strong, vibrant root system. The stem and leaf growth are slower.

Give ‘regular’ seedlings 16 hours of light and 8 hours of darkness to promote female plants. If seedlings are given more or less than 16 hours of light, higher percentages of male plants will grow.

Low levels of balanced light are exactly what seedlings need to grow. LED, fluorescent and compact fluorescent (CFL) lamps supply adequate light for the first 2-3 weeks of growth. Fluorescent tubes should be 2-6 inches above seedlings. Keep CFL lamps 12-18 inches (30-45 cm) above seedlings for best results. Place LEDs at the distance above seedlings recommended by manufacturers.

Consistent growing medium moisture is critical now. Too much water displaces oxygen and drowns roots, often causing roots to rot below ground and at the soil line (damping-off). Fragile roots dry out if they do not receive enough moisture. But given the perfect amount of water, seedlings thrive, growing faster and stronger every day.

From Seed to Seedling—A Comprehensive Guide from Seedsman and Jorge Cervantes

Courtesy of Seedsman

To accelerate root growth, keep soil 2°–5°F (1°–2°C) warmer than the above ground temperature. The perfect temperature is in the 77°–80°C (25°–27°C) range for the growing medium and 75°C (24°C) for ambient air temperature. You can place a heating mat, available at many hydroponic sites and stores, below seedling growing medium to regulate temperature.

Now is the time to cull out weak sickly seedlings. I always remove runt seedlings during the 3-5 week of growth. The extra space gives healthy strong seedlings more space to grow. But, some growers have so few seedlings they are forced to baby the weak plants until they become stronger.

Some growers grow seedlings with metal halide and High Pressure (HP) sodium High Intensity Discharge (HID) lamps. If you should decide to use a HID, a metal halide will supply a more balanced light spectrum. The limited HP sodium lamp spectrum causes stems to stretch. In any event, keep HIDs, which are much brighter than fluorescents, 3-4 feet (90-120 cm) above seedlings for best results.

The end of the seedling growth stage starts when the root system is established, and foliage growth becomes rapid. Plants now enter the vegetative growth stage and need more room to grow. The little plants must be transplanted into a bigger container to maintain rapid growth.

In collaboration with the author of this grow guide, Jorge Cervantes, Seedsman are delighted to be able to invite you to participate in their inaugural Photo Cup. With a cash and prize pool worth over $40,000, this is one of the largest ever competitions of its kind and is super easy to enter. Head to the Seedsman Photo Cup page now to get involved!

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