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How do I determine whether a plant is male or female?

Article Number: 331 | Rating: 4.6/5 from 30 votes | Last Updated: Tue, Jan 11, 2011 5:14 PM

Q: How can I tell the difference between a male and a female plant? Any tips or tricks I should know about?
Q: How does sexing work? What are the characteristics of male and female plants?
Q: When should I / can I determine the sex of my plants?

A: Mature cannabis plants are unmistakably male or female: male plants bear male flowers that resemble little ’bananas’, females bear the trichome-encrusted female flowers we all know and love. Of course, at this stage it’s far too late to separate the males from the females and prevent cross-fertilisation.

So how do you identify male plants at an early stage?

Method 1
Before you start the flowering period, plants will usually show pre-flowers. These generally appear around the fourth week of the vegetative period. Preflowers are very small indeed, so we recommend using a magnifying glass to improve the accuracy of your judgement.
The well-known image below clearly shows the different appearance of male and female preflowers:

It is very important to keep in mind though, that female preflowers do not always show clear pistil development. So don’t be too quick to ditch a plant without pistils! Determining sex on the basis of preflowering is definitely not 100% accurate and requires the right tools (magnifier) as well as some expertise.

Luckily, there are other methods to find out a plant’s sex.

Method 2
As soon as your seedlings have grown strong and big enough, you can take clones to determine the sex of the main plant. Make sure that cuttings are 1 1/2 inches in length or over, and have at least one node. Here’s how sexing with clones (ooh err) works:

Simple:
1. Label each of your plants (e.g. label your three plants A, B, and C).
2. Take a cutting of each plant and give each one the name of its parent plant (e.g. A, B, C)
3. Take the clones into a separate area, away from the vegetative plants, and force them to flower by starting a 12/12 light/dark circle.
4. As soon as the clones start flowering, you can determine the original plants’ sex (e.g. A=male, B=female, C= female)
5. Throw out the male plants and the cuttings.

Advanced:
1. Label each of your plants (e.g. label your three plants A, B, and C).
2. Take two cuttings of each plant, and give the cuttings the same label as the plant they came from (e.g. A1, A2, B1, B2, C1, C2).
3. Leave clones A1, B1 and C1 in your main growing area. If you want, put them under grow lights.
4. In a seperate area, away from your vegetative plants, force clones A2, B2 and C2 to flower by starting a 12/12 light/dark circle.
5. As soon as the clones start flowering, you can determine the original plants’ sex (e.g. A=male, B=female, C= female)
6. Throw out A2, B2 and C2, as well as the male plants and cuttings in your main grow area. You can then induce flowering in your female original plants and their clones as soon as you think they are ready.

Method 3
This method is a little fiddly, but very practical for growers who don’t clone and are not sure about determining sex based on preflowers.

1. Take a sturdy paper bag, or spray-paint a plastic bag completely black. Select a branch near the base of the plant you wish to sex. Make sure the branch is well away from your lamps to prevent heat build-up.

2. Take a plastic twist tie or elastic band, put the prepared bag over the branch, and tie it closed quite tightly. Make sure you don’t pinch off the branch.

3. Remove the bag after twelve hours, then put it back on after another twelve. Keep repeating this improvised light/dark cycle until the branch starts to flower. Determine whether the flowers are male or female and act accordingly. If the plant is male, be very careful when removing it and make sure you do not spread the pollen through your clothing or hands.

Method 4
Some growers will try to determine sex by force-flowering young plants in the vegetative stage, then forcing them to revert to the vegetative state again by returning to a 24/0 cycle. We do not recommend this method!
It will unduly stress the plants, causing them to stretch and take longer before they are harvest-ready.

One final note: if you grow feminised seeds, you will not have to determine the sex at all, which makes these seeds a great alternative for people who are unsure about sexing plants. Bear in mind, though, that stressing feminized plants may lead to hermaphroditism. Keep the temperature constant and optimal, prevent light leaks at all cost and do not transplant unless absolutely necessary.

Comments (1)

Comment By Anonymous - Fri, Apr 30th, 2010 2:34 AM

That was very interestingand helpfull thanks ; jim

I bought feminized seeds, but I found a male plant! What gives?

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