Sexing Mother Plants

M

Moosehead

Active member
I started a few plants from seed and want to keep the females for mothers. I have a few AK47, three Mighty freeze and 4 strawberry kush x blue dream, the latter is supposedly feminized but I want to make sure. I keep them under T5s and T8s 19 hours light and 5 dark. I heard that you can keep them in complete darkness for 2 or 3 days, turn the lights back on and the males will show sex very quickly.
I would be grateful if anyone familiar with this method can give me more info on timing, light intensity, etc.
 
Hey Moose, when did you start them? I find it's usually six to eight weeks after germination before they will show sex. Depends on the plant. If you're not in a hurry, relax, they will show soon. If you're in a hurry... relax, they will show soon!

I have never heard of forcing seedlings to show sex by leaving them in the dark for a few days, but it wouldn't surprise me, if they were close to maturity already. But that's the key: they have to be close already. You're not going to get tiny, new seedlings to show early imho.
 
Moosehead. I haven't tried that method for sexing, but I've heard it works. I'm interested to see how you do with it. That's a good one to know if it works well.
 
Sorry to take so long to get back. Anyway, experiment was inconclusive. I had taken out a few tall plants and several showed up as males early. After three days in the dark I turned lights back on and in four or five days they showed sex all right, all female. I since talked to a grower who plants seeds in January to get mother plants for cloning for an outdoor grow. He keeps them under 24 hour light until they are nearly mature and then leaves them in the dark for three days. After he turns the light back on the males show sex very quickly (in about 3 or 4 days I think) and are removed. He says he has been doing this for a number of years and it works good.
 
Moosehead said:
I heard that you can keep them in complete darkness for 2 or 3 days, turn the lights back on and the males will show sex very quickly.
Click to expand...

mmm, never heard that one but it is easy enough to test.

I've read several times that a 60-100x lope and a discerning eye can determine sex early.

Here is a bit of info you may find useful:

Male vs. female cannabis: How to determine the sex of your plant
Trevor Hennings February 11, 2020

In the world of plants, reproduction can happen in a variety of ways. Monoecious plants produce two different types of flowers on the same plant, and hermaphrodite plants grow single flowers that have both male and female reproductive organs.

Cannabis is a dioecious plant, meaning male or female reproductive organs appear on different plants.

With cannabis, females are usually isolated away from males—introducing males into a garden will result in pollination, causing females to create seeds.

This is important for a breeder to achieve new genetics, but most growers remove the males to allow females to produce seedless buds, also called sinsemilla. These are the resinous buds that appear on the store shelf; they all come from female plants.

Female cannabis pre-flowers grow as tiny bracts with hair-like stigma peeking out. Male plants produce small, round balls at the nodes.

Cannabis plants show their sex by what grows in between their nodes (where leaves and branches extend from the stalk). Pollen sacs will develop on a male plant to spread seeds and stigma will develop on a female to catch pollen. You can see these differences weeks before they actually start serving their purposes in the reproduction cycle. These are known as “pre-flowers.”

Pre-flowers begin to develop four weeks into growth, but they may take a little longer depending on how quickly the sprouting phase occurs. By the sixth week, you should be able to find the pre-flowers and confidently determine the sex of your plant.

Pre-flowers can initially be extremely small and hard to identify with the naked eye, but you can use a magnifying glass to get a better look. Examine the nodes of the plant and look for either the early growth of small sacs on a male, or two bracts on a female, which will eventually produce the hair-like stigma.

Though there are other methods to determine what sex the plant is, examining pre-flower formation is the most reliable.

https://www.leafly.com/news/growing/sexing-marijuana-plants
 
I have always been under the impression that they have to be sexually mature to determine sex. mj plants become sexually mature when the plant starts alternating nodes. That being said I know peeps have claimed that taking cloned seedlings and putting them into 12/12 to force them into showing is another method, although I have not done this myself nor have I seen it done:D

2b2s
 
Done it lots, a small plant at about 5 internodes can be sexed and show male or female before it alternates branches.

However, pure or almost pure sativas probably have to be mature to show sex. That's what I have seen and heard.
 
I like to let the plants mature and naturally show sex. I totally believe that this is where most hermi come from in seed stock. I think if you force a plant to sex it’s a major stress.
-ct-
 
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