Growing cannabis from seeds is a delightful experience. You start with the joy of selecting which seeds to grow from a world full of different varietals (“strains”), and then you grow them. People have found many methods, some better than others, for germinating cannabis seeds. Once you get them going, you want to give them their best shot at a vigorous start on their growing journey.
How to recognize cannabis seeds have germinated
You will know a seed has germinated by the emergence of a small white “tail” (the beginnings of a future taproot, known as the radicle). Of course, just like in the wild, you can start cannabis seeds directly in soil. If you want to follow that method, check out this article on how to plant cannabis seeds in soil.
How to prepare the planting medium (substrate)
Seeds need a clean, moist, but not soggy, environment to begin growing roots. If you don’t soak the substrate, it will pull moisture from the seed, depriving it of the water it needs to keep growing.
Did you know? Cannabis plant roots breathe oxygen below the ground! Healthy young cannabis seedlings develop structures that resemble hairs along the main taproot to access little pockets of air.
If the planting medium is too compacted or too wet, your germinated seed can suffocate or drown.
For this reason, pre-soak the chosen planting medium with care. Ideally, use trays with individual cells or pre-made cubes to prevent seed roots from becoming entangled with one another as they grow.
About 24 hours before you hope to plant germinated seeds, water the substrate from the bottom. This stops you from compacting the growing medium and crushing those important air pockets.
You will know it is well-moistened when the substrate has wicked moisture up to the surface level. It will be visibly darker than when it was dry. Remove any pooling liquid that remains.
Allow drainage and air circulation below the substrate. The day in between soaking and transplanting will give gravity a chance to release any excess water.
How to plant germinated cannabis seeds
Congratulations, your cannabis seeds have “popped”! Now what?
This step-by-step guide will give you the know-how to plant cannabis seeds after they have sprouted.
1. Prepare a hole for planting each germinated seed.
Plant one seed per hole in your growing medium. Place germinated marijuana seeds below the surface at least 0.25 inches (0.6 cm).
Rooting blocks or plugs made of rockwool, coconut coir (coco), or peat often come pre-drilled with holes. You have to make your own when planting into a loose substrate, like potting soil or soilless planting mix (for example, a blend of coco and perlite).
Next, make a “dibbler” (fun farmers’ name for “seed-hole-maker”). To do this, draw a line around a disinfected chopstick, sharpened pencil, or similar object with a pointed end at 3/8 of an inch (1cm) from the point. This depth accounts for the length of a bigger seed and its rootlet sitting in the bottom of the hole. It is better to plant slightly too deep than too shallow.
Press this tool into the substrate so the line you drew is at the level of the medium. This creates evenly-spaced holes of equal depth, one for each seed you intend to plant.
2. Plant seeds as soon as you notice they have germinated.
Check on your seeds frequently to ensure their rootlets do not grow very long or become dried out before they are planted. Ideally, they will be less than 0.125 inches (0.3 cm) long, very white, and plump-looking.
3. Place a single seed per hole, root tip pointing down.
Use sterile, blunt-ended tweezers for precision, control, and cleanliness.
Handle the seed gently and confidently. Grasp it by the still-attached shell and apply the minimum pressure to pick it up and move it.
Every part of your newborn marijuana plant is delicate at this stage. Take care not to squish the seed casing closed on the radicle, disturbing it as little as possible. Expose it to light and dry air for the least amount of time possible.
If your seeds germinate so vigorously that the casings have already come off by the time you check on them, very carefully lift the tiny marijuana plants by their developing stems below their first set of leaves (called “seed leaves” or cotyledons).
4. Fill in the tops of the holes with moist, loose substrate.
Do not compact the surface soil. Aim to match the texture above the seed with that below and around it — you want your seeds to feel safely enveloped, not crushed.
If using a structured cube made of coir, peat, or rockwool, ever-so-softly press the sides of the hole together to nestle your seed into place and ensure good seed-to-substrate contact.
5. Maintain substrate moisture and temperature.
Use a humidity dome and, if necessary, a very fine mist sprayer to retain surface moisture without compaction. A dry, crusty surface requires the seed to push harder to appear, using up energy that would otherwise go toward development.
Now, and for much of its life, your cannabis plants are growing both upward and downward simultaneously. The action of emerging from beneath the soil surface and straightening up is one of the natural mechanisms that loosens the shell once it is no longer needed to contain and protect the young plants.
How long will it take for cannabis seeds to break the surface?
What to expect when you’re expecting (sprouts!)
When to expect your cannabis seeds to sprout above ground depends on the seeds themselves and the conditions provided.
Be patient. Under ideal circumstances, seeds may take anywhere from several hours to 4-5 days to break the surface, but generally less than 10 days.
Just make sure the soil temperature is between 78 and 80 ℉ (25 to 27 ℃), and humidity is around 80%.
Want to get started right away? Get one of our grow kits! Follow the link below to get more information.
A Complete Grow Kit
- Everything you need to grow!
- 20 feminized seeds
- Marijuana Fertilizer
- Plant Protector
What does a healthy cannabis sprout look like?
As the little stem uncurls toward the light, the seed leaves (cotyledons) stretch open, pulling the head of the new plant free and exposing the central growth tip to the sky.
The stem of your new sprout will be small but sturdy. It will no longer be white but instead a mix of purple and green as it transitions from using nutrients stored in the seed to converting light energy to food.
Soon after, the first set of “cannabis-looking” or “true” leaves will grow. Success!
Troubleshooting: things that can go wrong when planting germinated seeds (and how to fix them)
Why are my seedlings taking so long to show up?
When cannabis seeds take a long time to emerge, a too-dry or over-watered substrate at the wrong temperature is often to blame.
Use the finest mist possible if lights are drying the surface of your soil, and always ensure adequate drainage, keeping soil temperature in the 78-80 ℉ (25-27 ℃) range.
Avoid the temptation to dig around for your seeds; it will only increase the likelihood of damaging their delicate roots.
Why did my seeds push themselves entirely out of their holes?
This is called ‘heaving’. When a seed’s root does not dig into the substrate, it can be the result of shallow planting or poor “seed-to-substrate” contact. A too-tightly compacted, too-wet or too-warm subsoil environment can also be the cause.
If your seed’s tail has grown quite long and is starting to straighten out, it is already forming its stem. Use your tweezers to very gently re-plant the seed with the developing taproot pointed down and its head just at the soil surface.
Check to make sure you are providing ideal environmental conditions to support continued growth.
Want to make sure to get the best start with your grow? Take a look at our grow bible below, so you know all the ins and outs of germinating and growing your plants!
Where did my germinated seeds go?
Damaged radicles, damping off, and IPM (integrated pest management) issues are generally responsible when healthy germinated seeds don’t appear after planting.
All you can do is tighten up your process, implement better cleanliness and grow protection strategies (especially if it looks like rodents dug up and escaped with your seeds), and give it another try.
You may want to practice sprouting and planting seeds similar to cannabis, like buckwheat, to build confidence and see if you have created a more optimal starting environment. (Bonus: buckwheat microgreens are delicious and healthy! Since they’re inexpensive, purchase a lot of them; you can get plenty of reps in and build your seed-moving muscle memory.)
Final Thoughts on Planting Germinated Cannabis Seeds
Remember that although dormant, a seed is already alive before you plant it. Smooth and careful handling through each of its first stages of growth sets a cannabis seedling on the right path.
Practice, precision, and consistency allow you to compare seed vigor, improve your technique, and fine-tune your growing environment.
Want the info you need for seed-to-harvest all in one place? Download Robert’s Grow Bible. For the finer details on how to grow cannabis from regular, autoflower, and feminized seeds, make sure to check out the Grow Guides here at ILGM and jump on our Forum for more tips and support!
Xavier
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