How to Harvest Seeds From a Cannabis Plant (and Germinate Them)

To harvest seeds from a cannabis plant, let a pollinated female keep flowering until the seeds turn plump and dark, often with tiger-stripe markings (usually around six to eight weeks into flowering), then dry the buds, crumble them and collect the seeds that fall out. Store them in an opaque, airtight container until you're ready to plant. Not long ago, nearly every bud came with seeds, but as growing evolved, so did demand for "sinsemilla," high-quality seedless cannabis, and breeders started specializing in producing seeds on purpose, both to develop new strains and to distribute them widely.

Breeding the perfect strain takes controlled seed production. Breeders have to get their favorite plants to produce pollen and then use it to pollinate other favorites, creating "crosses" of the two chosen parents. Growing seeds is a precise process that requires clean, controlled environments that are completely sealed off to keep outside pollen out.

Once the pairings are chosen, the plants can be vegged, meaning kept in their vegetative growth phase if the goal is to make them bigger before seed production starts, but that's optional. Once the plants are big enough, they're switched to a flowering light cycle of 12 hours of light and 12 hours of total darkness.

Within a few weeks, the male will develop pollen sacs that soon burst, sending pollen through the air to fertilize the females. The females will then produce seeds that can either go back into the breeding program or be harvested.

How cannabis makes seeds naturally

Cannabis is an incredibly tough plant, and it doesn't always need a male to make seeds. Evolution has given it an amazing ability to pollinate itself when there are no males around to do the job. Whether it's stressed or old (for example, a female left well past her prime instead of being harvested), if a female senses that her environment isn't good for long-term survival, she'll produce seeds in the hope of passing on her legacy.

That's how feminized cannabis seeds are made. Breeders carefully stress a healthy female plant to "trick" her into thinking her life or safety is at risk.

Why are there seeds in your buds?

Seedless buds are the goal, but in reality, anything can happen. So why do some of your buds end up full of seeds? There are usually a few reasons. Basically, when pollen from male cannabis plants reaches the pollen-catching part of a female plant (her pistils), she starts forming seeds in her buds.

As a grower, once you notice this, you need to pull the male plants and any hermaphrodites so you get weed with the highest possible cannabinoid concentration.

How do you get seeds out of a plant?

Most grow operations aim to keep seeds out so they can grow fine sinsemilla, but sometimes breeders want seeds. Whether it's for their own gardens or to sell to picky customers, seed growers are after healthy, happy seeds rather than big, beautiful buds. So what's involved in pulling seeds from your weed plant?

Seed crops are harvested when the seeds are plump and dark, often with a tiger-stripe pattern (around six to eight weeks into flowering).

After harvest, the buds are dried and the seeds collected. Small-scale seed harvesting is as simple as crumbling the dried flower and catching the seeds that fall out.

Commercial seed harvesting usually involves special machines that grind up the dried flowers and sort the trim and seeds into separate bins. Once collected, the seeds are stored in opaque, airtight containers to keep them from rotting or sprouting too early.

Cannabis flower is usually grown seedless, but sometimes the seeds are the whole point. When breeders grow cannabis specifically for seeds, they pay close attention to pollination, harvest timing and drying to boost the odds of a successful seed harvest.

How do you germinate cannabis seeds?

Germinating cannabis seeds is a relatively quick and easy process, but there are a few important factors to keep in mind if you want the highest germination rate possible.

Once you put a seed in a moist growing medium, it kicks off a series of reactions that lead it to germinate within a few hours or days.

Whatever medium you're germinating in, never let it dry out completely. If the seed stops sensing moisture around it, it'll most likely shut down and never sprout.

Check every day that your germination medium is still moist; it's an easy way to avoid nasty surprises. If you're growing hydroponically, it's always best to germinate in rockwool cubes, which of course need to stay moist the whole time.

To avoid problems, the best time to plant your seeds is when the taproot is 1 cm long, 2 cm at most (under an inch).

Soil or paper towel?

If you bury the seed directly in soil, you risk planting it too deep, especially if you water the medium after you've sown it.

The safer bet…

You'll get much better results germinating in paper towels or peat pellets. Once the seedlings pop, you transplant them into your growing medium.

Cannabis seeds germinate best with relatively high temperature and humidity.

At certain times of year especially, you'll need some kind of heat source to reach a temperature of about 26-28 °C (79-82 °F).

Ideally, keep your germination medium at about 26-28 °C and around 70% humidity

To germinate with paper towels, make a sandwich with a plate and the paper as shown in the image, and once the seed sprouts and the root reaches a centimeter or two, move it to your growing medium. It's a safe method because you can check on the seed just by lifting the paper.