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how to tell the sex of a cannabis seed

Keeping in mind that every strain and grow set-up (e.g. indoors, outdoors, daylight hours) creates varying circumstances, most cannabis plants begin to pre-flower as early as 4 weeks after germination. By week 6, the pre-flowers begin to reveal their gender and you should be able to identify the sex using the tips to follow. Once the plants go into full flower (8 to 10 weeks on average, for a natural outdoor grow) the differences between male and female plants will be glaringly obvious. We’ll talk more about exactly what each sex looks like in a moment.

Until we can tell the sex for sure, we continue to treat the plants equally. We start our seeds in small 4-inch nursery pots. About two weeks after germination, we pot the seedlings up into an approximately two-gallon (trade size) “sexing pot” like these BPA-free nursery pots. This enables everyone to continue to grow in a happy and healthy manner for several more weeks*. Then, once we can surely tell the difference between the male and female cannabis plants, only the ladies move into their forever home – 15 to 25 gallon grow bags full of recycled organic living soil. To learn more about our soil recipe and how we maintain it, see this article.

In order to correctly sex cannabis plants, you’ll need to become familiar with their anatomy in general. Both males and females produce pre-flowers and flowers in the junctions between stems or branches. The very first pre-flowers show up in the crook between the main plant stalk and a fan leaf stem (petiole), usually near the top of the plant. The good news is, the males usually begin to develop and show sooner than females. I guess the idea is that the dudes want to have their pollen ready and waiting for when the ladies join the party?

Identifying a Male Cannabis Plant

If you are growing from feminized seeds, you shouldn’t need to worry about sexing your cannabis plants all that much. While not 100% guaranteed, there is only a very slim chance that a feminized seed will produce a male plant. About 1% in fact. In all of our years growing, we have never had a cannabis plant grown from feminized seed turn out to be a male – though we only grow a handful of plants per year. Folks who grow hundreds of plants could potentially end with a rare male now and then.

Repeated colloidal silver treatments cause repression of the plant’s ethylene, which is the stuff that creates male flowers. Instead, the treated female plant will grow pollen sacks full of FEMALE pollen (XX rather than XY). Then breeders use the female pollen to pollinate female flowers, resulting in the development of all-female seeds.

However, the culled males don’t need to go to waste! One option is to chop up the male plant and use it to mulch other plants – much like we do with borage, fava bean greens, yarrow, and comfrey. You could also juice the leaves, which are full of nutrients. Heck, you could even steep the plant material in water to create a natural fertilizer as we do with stinging nettle. Finally, I’m sure your compost pile will welcome the male plant with open arms. Or would that be… with open worms?

Aside from the clear-cut flower differences, there are a few (potential) trending characteristics between male and female cannabis plants. In many cases, male cannabis plants tend to be more gangly. They may be tall, narrow, have fewer fan leaves, and longer spacing between branches – also referred to as greater inter-nodal spacing. On the flip side, female cannabis plants are usually more compact and bushy than males.

Feminized seeds are actually bred to have a 99.9% chance of being female. It is possible still for these feminized seeds to hermaphrodite if the plant experiences high stress during its growth cycles. Feminized seeds remove the need to check the sex of your plant, no need to worry about fertilization!

The weed that we consume is produced by the female plant only. If there are seeds in your bud, that means there may have been some interference from a male plant nearby.

With cannabis plants, breeding two different strains together will have the same result. For example, the strain “Blue Dream” is a mix of the strains “Blueberry” and “Haze”. It can be fun experimenting with breeding different strains together because you will get a genetically different plant each time!

Want to Make a New Strain?

The male plant start to produce a pollen sac at their nodes while the female plants start to produce stigmas, which spreads out and catches the pollen. You may be familiar with the orange/ amber hairs on a cannabis nug.. Those are the stigmas!

Most plants will show their sex during this pre-flowering time period, others are a little more stubborn. If you have planted a regular seed (not feminized) you could start noticing male/female genetics as early as 4-6 weeks of age.

We do not recommend auto-flowering seeds for Grobo – feminized is your best bet. This is because auto-flowering seeds can be unpredictable, and may start to flower when the plant is too small, or too large and outgrowing the Grobo.

Plants have several different ways to reproduce. The most common method is sexual reproduction. Plants that reproduce sexually with seeds are called angiosperms. Approximately 80% of green plants identified on earth are angiosperms, including cannabis.