This blog shows you how to germinate marijuana seeds in three easy steps. Seeds must be viable to germinate and develop into strong healthy fast-growing seedlings. The key for your seeds to get off to a good start is to supply the proper levels of air, heat, water and darkness. Choosing the proper substrate or rooting block/plug will help ensure the small delicate root system receives the proper levels of moisture and oxygen (air) for rapid growth. Auto-flower seed and seedlings require special care to ensure a heavy harvest.
This garden of female photoperiod plants was grown from seed that has been selectively bred for generations to acclimate to the local conditions. The grower, Humboldtlocal, germinated seeds that grew into seedlings that suffered no stress.
Seeds contain genes from the flowers of each parent, male and female. Genetically unstable seeds grow into “intersex” plants, AKA hermaphrodites, bear both male and female flowers on the same plant. The genes within a seed also 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 cannabis seeds also dictates whether they are regular with male and female flowers, feminized with only female flowers, photoperiod plants that require long 12-hour nights to flower or auto-flowering that flower regardless of the amount of light or darkness during a 24-hour period.
All seeds have the same basic requirements for germination and seedling growth. Strong healthy parents, proper breeding practices, and excellent care will yield strong seeds that germinate well. Strong seeds produce healthy plants and heavy harvests. Seeds stored under adverse conditions (hot, cold, or humid) or stored too long will germinate slowly and have a high rate of failure. Vigorous seeds initiate growth within a day or two. Some seeds take longer to germinate. Seeds that take longer than a month to germinate might always be slow and less productive.
Viable vs Unviable Cannabis Seed
Viable cannabis seed is typically darker beige, brown to almost blackish in color. Most often seeds are spotted or mottled and appear somewhat shiny. Harvested cannabis seed that has been treated properly – stored in an airtight container and not scuffed up – after harvest still contains a thin waxy protective coating that gives it a healthy luster. This waxy layer is one of the reasons that viable cannabis seeds float for an hour or two before sinking when soaked in water.
Fresh dry cannabis seed loses viability over time. Seeds have a hard outer shell that cannot be easily crushed when squeezed between your fingers. Seeds are typically roundish with one end a narrower with a slightly teardrop shape. Seeds usually retain a high rate of viability for the first few years.
Strong viable cannabis seeds are easy to distinguish from greenish immature seeds.
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 ger- minate poorly and often produce sickly plants. Healthy, fresh, dry, mature seeds less than a year old sprout quickly and grow robust plants. Weak cannabis seeds germinate poorly and if they sprout, they usually grow into sub-standard plants. Weak seeds look fragile and are typically light beige to brown in color. They are often immature and not completely formed. The outer shell on some weak cannabis seeds never properly seals. The faulty seal lets moisture moisture and air penetrate. This “false start” dissipates hormone concentrations and seeds become less viable or completely useless. Once water and air penetrate seeds, diseases and pests have an opening to to move in. if the seed is easy to crush when you lightly squeeze it between your thumb and finger, it will not germinate.
Air, Water, Heat and Darkness
Seeds need air to germinate. Moist, soggy growing mediums will cut off oxygen supplies; seeds will literally drown if totally submerged for more than 20 minutes after germination. Planting seeds too deeply also causes poor germination. Seedlings do not have enough stored energy to force through too much soil before sprouting. One rule of thumb is to 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. I like to explain it as putting a very small dab of soil on top of the seed and keep it evenly moist. I like to set a moist paper towel on top of the soil until the seed emerges, see below.
Household water often contains enough dissolved solids (nutrients) to nourish seeds through their first few weeks of life. But household water may cause problems. Seeds are very sensitive to excessive salts in water that disrupt internal chemistry. I prefer to use distilled or reverse osmosis water that contains virtually no dissolved solids to germinate seeds. Watering seeds with a nutrient solution can inhibit germination.
Temperature range germination 72-79ºF (22-26ºC)
Humidity range germination – 95-100%
Seeds need heat to germinate. Seeds sprout without light in a wide range of temperatures. Properly nurtured seeds germinate in two to seven days, in temperatures from 70-80°F (21-26.6°C). Temperatures above 85°F (29°C) impair germination and could lead to rot. Temperatures below 70°F (21ºC) slow germination. Below 60ºF (15.5 ºC) seeds stagnate and if the environment is too wet, disease could become a problem. Super hard seeds may need to be scarified (see below) to help initiate germination.
Seeds need total darkness to germinate. The rootlet or radical is the first to emerge. It needs darkness so that it can anchor the plant that will emerge aboveground. Bright light shining on a tender little rootlet can stunt growth and in extreme cases result in failed germination.
Secure an emery board inside of a small box.
Close the box with the seeds inside.
Shake the box for a few seconds to scarify seeds.
Scarify/scuff seeds with a hard outer shell 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 10-20 seconds. Do not overdo it or you could damage the seeds. Remove the seeds and make sure they have been scuffed. Just a little scuffing will allow water to enter and set germination in motion. Scuffing can increase germination success rate, especially if seed outer shell (testa) is thick and hard.
Soak cannabis seeds in a 3 percent solution of hydrogen peroxide (H2O2) for 20-30 minutes to help break down the durable outer shell. Soaking in H2O2 also kills any bacteria, fungi and other pathogens that might be on the surface of the seed.
3 Steps to Germinate Cannabis Seeds
Seeds float before the water tension is broken and moisture penetrates the outer. Growth hormones are activated once water enters the inner seed. Seeds sink as more and more water soaks into the interior.
1. Soak seeds overnight in a glass of low EC or distilled water. Make sure seeds get good and wet to activate growth. At first seeds float. Seeds sink to the bottom as moisture penetrates the outer shell. Do not let seeds soak more than 24 hours or they suffer oxygen deprivation and drown. Once soaked carefully place seeds inbetween moist paper towels on a saucer or plate.
Here is a selection of germinating seeds from Spain. All of the germinating seeds were given away free with Cáñamo magazine.
2. In a warm, dark location (70-85°F, [21-29°C]), place seeds in several layers of moist paper towels on a saucer or plate. You may need to add a little water to the plate daily. Be vigilant of warm nights that cause paper towels to dry. Let excess water drain away freely. The paper towels will retain enough moisture for the seed to germinate within a few days. The seed contains an adequate food supply for germination. Prevent fungal attacks by watering with a mild organic surface fungistat solution.
Note: you can also put the wet paper towels containing seeds in a plastic bag. The bag functions as a mini greenhouse to retain moisture. Make sure the plastic bag remains open to ensure adequate air exchange.
When water penetrates the outer protective shelldormant hormones that induce germination and plant growth are activated. A constant stream of moisture is essential to transport nutrients, hormones, and water to carry on life processes. Letting germinated seed suffer moisture stress now will stunt, even stop growth.
Once cannabis seeds start to germinate, root growth can be very fast. Make sure to plant germinated seeds before the rootlet grows too long like the ones above. These sprouted seeds will suffer much stress when planted. The tiny delicate root hairs will be damaged causing stress and a slow start on life. Always plant germinated seeds before tiny root hairs appear to minimize stress.
Once the radicle starts to grow, the seed is ready to plant into the substrate. When seed is planted, gravity will direct root growth downward and light aboveground will provide energy to start photosynthesis. First a set of rounded cotyledon or seed leaves appear. Next, a pair of serrated cannabis leaves grow on the internode above cotyledons.
3. Remove germinated seeds when the little white rootlet grows from 0.25-0.5 inches (0,6-1.25 cm) and plant in substrate with the rootlet pointed downward.
Seed Blocks, Cubes and Substrates
Preformed Root cubes are made from rockwool, peat pellets and Oaisis blocks. Planting germinated seeds in these preformed blocks make growing seedlings and transplanting them later very easy and trouble free. All three of these seedling cubes encourage strong root system growth.
This seedling flat is designed to hold 60 Jiffy peat pellets. Add water to hydrate and expand the peat pellets
Peat pellets are small compressed peat moss containers with an outside expandable plastic netting wall. The flat dry pellets pop up into a seedling pot when watered. Do not let the roots grow through the netting that on the outside of the peat pot. Remove this netting before transplanting so that root growth is not restricted.
Plugin Pro Extract seed plugs and pre-filled flats are made with a combination of peat, coco coir and a binder. This lightweight combination promotes plenty of air and drainage in the growing medium. The spongy consistency of the plug makes it easy to extract and transplant without damaging the root ball.
Polymer-bound seedling plugs are very popular, including “Rapid Rooter Cubes”, “Ellepots” and “Flora Root Plugs”. These sponge-like plugs bind coco coir, peat, etc. together to form a seed plug or cube that adequate air and nutrient solution for outstanding seedling growth. The low-maintenance plugs can be purchased in bags or seedling trays ready to plant.
Soilless and potting soil seedling mixes contain fine particles that hold a little more water. These mixes can be pressed into blocks, but that is a lot of work. Fill cellular seedling trays or small containers with the fine seedling mix. Transplant germinated seeds into fine soilless mix or seedling potting soil and remember to keep the surface evenly moist. Be careful to avoid overwatering.
Rockwool root cubes retain are a favorite of many hydroponic and Deep Water Culture (DWC) growers because it retains structural integrity during the entire crop. But rockwool must be treated – hydrated and conditioned. The cubes must be rinsed and soaked overnight in a low pH to 5.5-5.8 nutrient solution over night.
In rockwool seeds can “heave” (crawl out of the rockwool) during germination. Planting sprouted seeds with a longer white radical (0.5 inch (1.5 cm)) in rockwool avoids heaving. Take care not to expose the tender rootlet to prolonged intense light or air. Keep the growing medium evenly moist. Once the taproot sprouts, small fuzzy feeder roots will grow in a few days.
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 a heavy layer of soil before sprouting. Plant seeds twice as deep as the width of the seed.
Transplant Germinated Seed
Transplant sprouted seeds when the white sprout is visible. I like to move the sprouted seed into a seedling block or mix soon after the white radicle becomes visible. The little white tap root, when long, is more difficult to keep evenly moist. Dangling rootlets are easy to damage and should not be exposed to air and light for more than a few minutes.
Avoid touching, squeezing, scraping, fondling, etc. delicate rootlets with filthy hands to avoid injury. Move seeds with tweezers or shuffle them out of the paper towels into the planting hole to avoid disturbing rootlets.
To transplant, carefully pick up the fragile sprouted seeds with your clean fingers or tweezers and plant them in a pre-drilled shallow hole in the soilless mix, small seed pot, peat pellet, rockwool rooting cube with the white root tip pointing down. Cover the germinated seed with a very light, 0.25–0.5-inch (1-2 cm) of moist soilless mix, peat or other substrate.
Small growers can take the time to plant individual germinated seeds with tweezers. Avoid touching the little white rootlet with your dirty, rough hands. It is super delicate now and easy to damage.
Keep the sprouted (germinated) seed evenly moist. Please see our upcoming blog “3 Easy Steps to Grow Perfect Cannabis Seedlings.”
Auto-flower Seeds Require Special Care
This auto-flower seedling was transplanted to the final container before the roots were visible on the outside of the Jiffy peat pot. The delicate roots and root ball suffered no stress during transplanting.
Start auto-flowering plants in a Jiffy-pot, rockwool cube “Ellepot” https://www.ellepot.com and “Rapid Rooter” cubes to transplant outdoors or to a larger container. The container must be rigid so that the root ball remains intact. AvoidStyrofoam and hard plastic trays. Auto-flower roots suffer stress as soon tips hit the sides of containers.
Transplant autos as soon as roundish cotyledon leaves start to emerge, or a day before they emerge. This will help guard against roots poking through the sides of the rigid container. I´m always amazed at how a little root movement will decrease yield in auto-flower plants.