How to Germinate Cannabis Seeds

Sophia Delphi May 12, 2022 - 7 min read
Fact Checked
Stages of cannabis germination from seed to sprouting phase

Even diehard backyard gardeners face a learning curve when they decide to produce their own weed. Growing weed requires much more attention to detail than growing cucumbers or zucchini.

And when they visit any cannabis resource site (including ours) looking for pointers, they’ll read more about the process of growing weed than they could ever want to know.

There will be pages and pages about lighting and ventilating a grow room, the right mix of nutrients for every stage of the growing process, and the right way to dry and cure marijuana once it’s been harvested.

However, it’s tougher to find information about what might be the most important phase of the process: the cannabis seed germination and sprouting phase.

Let’s dive into that subject now.

You Don’t Always Have to Worry About Germination

There are two ways to begin cannabis grow: with seeds or with clones.

Cloned plants are sort of like the pre-started tomato plants you can buy at your local garden center. They’re already growing, and all you have to do is put them into your growing medium. There can be one important difference, though.

Many of those tomato plants are grown from seeds in a nursery. Cloned weed plants, by comparison, are all cuttings from a “mother” plant and are exact genetic copies of their parent. So their characteristics — and their sex — are guaranteed in advance.

If you plant clones, you don’t have to worry about choosing the right seeds. More importantly, you can cut weeks off of the growing process since you don’t have to worry about proper germination and sprouting.

There are also downsides to clones. They’re more expensive, the right plants can be hard to find, they may not react well to transplanting, and they may bring in diseases or pests from wherever they were started.

Then, there’s the “Mr. Green Jeans” factor: many people find growing from seed the more satisfying experience. Controlling the entire process from seed to harvest is why many people want to grow their own plants in the first place.

If you’ve chosen to go the seed route, you’ll have to pay careful attention during the germination and sprouting phases of your crop. Here’s a road map.

Cannabis Seeds

We won’t spend much time on how you should choose the seeds you plan to grow; that could require another full article. You’re safest purchasing feminized seeds from a well-known seed bank, where quality is paramount, and the selection is large. By contrast, there’s usually no way to be sure where the seeds sold at dispensaries are sourced from.

You’ll also have to decide on the strain you want to grow and whether you want to start with regular or auto-flowering seeds. Autoflowering strains are often less potent, but they are easier to grow, and they’re ready for harvest much faster.

Once you have your seeds, the first step is germinating them.

How to Germinate Weed Seeds

Seeds are essentially hibernating plants. When you germinate them, you’re giving them a signal that conditions are right for them to emerge. Moisture and heat are their primary cues, which is why seeds should be stored in a dark, cool, dry place until you’re ready for them to “pop.”

When you’re ready, there are several methods you can use to germinate your seeds.

On a Paper Towel

This is the method commonly used by small-scale growers.

  1. Take two pieces of paper towel, and sandwich a few seeds between them. Place the “sandwich” on a flat surface and moisten it well, using a spray bottle filled with water.
  2. Carefully place the paper towels in a plastic freezer bag and keep the bag in a dark room or closet, at room temperature, for a few days. (Some people put the paper towels between paper plates and cover the plates with a bowl instead.)
  3. In a few days, the seeds will pop out tiny roots. When the roots are about ¼ inch long, the germinated seeds are ready to be potted.

Caution: Be very gentle when moving the seeds. It’s best to use tweezers.

In Soil

This might sound easier, but it really isn’t. Here’s why.

You can’t start cannabis seeds in “regular” soil; you have to use seed-starting or potting soil, which contains the proper nutrients and is calculated to be at the right pH (around 6.0) for germination. In other words, you’ll still have to re-pot the seedlings.

  1. Put the soil in a small pot, and use your finger to make a half-inch deep hole.
  2. Put a seed into the hole and lightly cover the hole with soil.
  3. Place the pot under fluorescent lights at room temperature and water daily with a spray bottle. If the soil gets dry, water more often.
  4. You’ll see the seed sprouting in less than a week. When the sprout is 2-3 inches tall, transplant it into a bigger pot.

In Water

Why would you want to germinate seeds in water? If you were reading carefully, you already know the answer. Moisture is the primary sign to the plants that it’s time to sprout, and the water softens their shell. So seeds placed in water will germinate in just 1-2 days.

  1. Fill a medium-sized glass with water. Be sure it’s at room temperature before proceeding.
  2. Put your seed(s) into the water, no more than two seeds per glass.
  3. Change the water every two days.
  4. Sprouting should begin in a few days, although older seeds can take as long as seven days for their small roots to emerge.
  5. The sprouts can be moved into the soil after another day or so and should definitely be transplanted by the time they’re ¼ inch long. Again, be careful and use tweezers.

Transplanting Seeds Once They’ve Sprouted

Before we go any further, some earlier advice bears repeating once more: be careful. Newly-germinated seeds are very fragile, and it’s way too easy to accidentally break off their roots.

  1. Fill a one-gallon pot with your chosen growing medium, which for new growers will usually be soil. So-called “living soil” is preferred by many growers, but regular soil will work fine.
  2. Water the soil thoroughly, but don’t douse it. The soil should be wet, not dripping wet or muddy.
  3. Make a hole in the soil that’s twice as deep as the seed’s width.
  4. Gently place the seed into the hole with your tweezers. Be sure the roots are pointing down, not up.
  5. Cover the hole loosely with soil. Don’t pack it down firmly.

Use your spray bottle to water the seed until a seedling appears, which will take about 5-7 days.

Congratulations! It’s a weed plant!

The Cannabis Germination and Sprouting Phase: FAQ

Q: Why can’t you just put the seeds directly into the ground or the pots you plan to grow them in?
A: Unfortunately, cannabis seeds are extremely sensitive. The nutrients that are in regular soil could kill the plants or sprouts, and direct sunlight immediately after germination could do the same thing. There’s no reason you can’t do it, of course, and many people do. However, expect a much lower successful germination rate if you don’t baby your seeds until they’re ready to be transplanted.

Q: Can you grow weed from a bagseed?
A: For those who have never heard the term, a bagseed is simply a seed you find in your weed stash. Baggie…bagseed…get it? Those seeds aren’t likely to produce primo weed if they sprout at all, but occasionally you can get lucky. If you plan to try it, look for seeds that have a solid shell that doesn’t crack when you squeeze it lightly. If you find one with “tiger stripes” on the shell (dark stripes running along the seed), that’s your best shot at growing a decent weed plant.