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Hydroponic Marijuana Sexing

How to sex marijuana

Marijuana sexing simply means determining the gender of your marijuana. While cannabis occasionally may be hermaphroditic (having both pistils and stamens), generally, plants are wholly male or female.

After four or five weeks you will start to have a chance at sexing the plants. Although generally considered one of the trickiest parts of growing your own marijuana. Marijuana sexing is quite straightforward and will become easier as you gain more experience. The reason for sexing your plants is so that you can remove male plants before they have a chance to pollinate the females. If this occurs the females will start to develop seeds and this will divert their energy from THC production. Which if course is not cool.

Left to their own devices plants will develop pre-flowers after around 4 – 6 weeks. This is the right time to remove the males and commence the flowering stage.

Marijuana is a dioecious plant which simply means that the males will produce pollen and the females will produce seeds. Although, as in other forms of life, hermaphrodites do occur.

Why is this important?

Unless you are a breeder or otherwise growing for seed stock, it is preferential to have all female plants as it is the unfertilized calyx or buds  which are the most psychoactive and potent part of the plant, the THC, CBN and CBD. So your seedless buds (sinsemilla) are the most preferred harvest for smoking as no energy or weight has gone into making seeds. Therefore, to use energy, time and space on male plants is wasteful of limited resources; thus they should be identified as early as possible and either segregated (for breeding) or destroyed before they release their pollen.

Occasionally marijuana will show pre-flowers (immature indicators of the sex of the plant) while still in the vegetative state, but generally require the shift to the flowering phase (shortening the light regimen to 12/12 – 12 hours of light and 12 hours of total dark).

Male preflower

Flowering is the only true way to sex your plants

Although you may get a clue from their growth patterns before flowering. Male cannabis plants tend to be leggier than female plants with a longer internodal length. Female plants are squatter with more leaves and a bushier aspect.

Male pre-flowers should be clearly visible to the eye, although a magnifying glass will make your job easier. Male flowers form at the junctions of the branches and stem and the pollen sacs form little balls.

Male preflower

Female pre-flowers will also form at the junction of branches and stem but will normally start to form at the fourth or fifth branches up from the base. They are easily distinguished by the appearance of pairs of tiny white hairs, known as pistils.

Female preflower

Some growers force flowering by changing the light cycle before the appearance of pre-flowers. They then watch their plants closely for the appearance of flowers and remove the males. However, others believe that this can stress the plants and is not a proven way of speeding up the process as plants forced in this way may spend longer in the flowering phase, cancelling out the advantage.

Identifying gender

A magnifying glass is helpful though not necessary. Look near the top branches right where they fork from the stalk. The male sex organ will look like a small playing card-type club. The female sex organ will display a calyx with two small white hairs protruding from the top. If you are unsure or unable to determining the sex, then simply wait a few more days until the organs are more mature and easier to identify. The males are still way too young to create pollen so there is no danger in waiting.

Male and Female Marijuana

Early sexing

There are two ways to tell the sex of a plant earlier than the plant would normally reveal its gender.

  1. Force flowering by putting the plant under 12/12 light cycle. The drawbacks of this are that two separate rooms or grow spaces are required. More importantly the plant gets hormonally confused being switched between vegging to flowering, then back to vegging and finally flowering once again. This method allows you to cull your males early, but most likely will delay your harvest for a few weeks.
  2. Cover a lower branch with black plastic cut from a garbage bag. Do not use a thin bag that allows light to pass through. This must be put on every 12 hours and removed every 12 hours at the same time. The branch will show its sex long before the rest of the plant while still allowing it to ‘veg’ otherwise normally.

Female preflower


Occasionally a plant will exhibit both sexes. This usually occurs when a female plant is late into flower and remains unpollenated. In a last ditch effort to create seeds, marijuana plants have an emergency back-up plan: they sometimes create a small number of male flowers in an attempt to pollinate themselves. Some growers pinch off the few visible ‘bananas’; others may remove and/or destroy the plant so as not to pollenate a whole crop.

Marijuana sexing is not difficult once you familiarize yourself with some basic plant physiology.


Cloning marijuana is a great method to use as all shoots are genetically identical to the parent. Thus if you find a donor parent  plant that you like (one with desirable genetic traits) and is large and healthy enough to remove branches for cuttings, you may skip the whole sexing ritual as they are 100% the same sex as the parent.

Feminized marijuana seeds

These are a relatively new phenomenon on the cannabis culture scene, and while looked down upon by some old-timers, purists and large-scale growers, are a great boon to the small grower with limited space and time.

It is currently not possible to tell the sex of a cannabis seed by examining it (though many untested myths abound), but the mix of males and females is roughly half and half. The larger the amount of seed purchased and/or planted, the closer the ratio will be to 50%. However, if you purchase a small quantity such as five seeds, it is possible to get all males, all females or any mix in between.

Feminized marijuana seeds are not foolproof nor 100% guaranteed, but ratios of 90%+ female are quite common.

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22 thoughts on “Hydroponic Marijuana Sexing

  1. Luftwaffe65 says:

    I bought some good bud. Smells very citrusy and its nice full, thick buds. Def a good buy. I found 6 seeds in the buds. This score is from a hermaphrodite yes? I am starting a hydroponic grow. Tent, led lights, bubbleponics. Seeds from a plant like this will grow and if female, will turn out (if I do it right)like the stuff I am smoking that I bought? I love it, its great smoke. thick, sweet smoke and helps me sleep. Any advice? Thanks

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  2. Holland Grower says:

    The most direct observable & important traits of male cannabis best to breed with are as follows:

    1. Resistance to hermaphrodism
    2. Vigor
    3. Stature
    4. Maturation rate

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  3. smokeman says:

    Grow my on plant need help. Have a 23 day plant

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  4. jayrok says:

    thanks for the info my Question is how long after u see the signs of it being a female due the buds start to come

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  5. Pat says:

    Which sex of the plant gives you the THC?

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    Rating: -2 (from 2 votes)
  6. dobie says:

    Which sex of the plant will generate THC?

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  7. Badger says:

    Hi First timer
    Sounds about right. 8 weeks might be quite long in the veg stage, depends on the strain, a lot of plants really stretch during flowering so if space is an issue at all I would think about switching to 12/12 sooner. If you’ve got lots of room then let them go the 8 weeks and count on somewhere around 7-10 weeks for the flowering stage to finish.
    Don’t forget to change your feed to a bloom formula.

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  8. Don says:

    Where do i get the seeds to start up? and how do you know the diference of male and female seeds?????

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  9. firstimer says:

    i have planted seeds i got from my stash n the are flourishing, 4 weeks from seed now, I have no idea what type of plant or length of growth cycle. I was planning to have atleast a 8 week vegetative stage, then reduce lighting to 12 n 12 to begin the flowering stage, does this sound right and about how long is the flowering stage.

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  10. roachman4/20 says:

    some 1 help me i stated 3 weed plants and 1 of the stems broke and i took the step and put the stem that was still on it back in the dirt and its still growing and im just germanated the seeds about 2 weeks ago and i just water it and try to keep it under light and 1 of the plants that grew about 1 inch up from the 2 leaves the plants stem is abot 3 inchs long and it keeps slumpin over and i put a pencle next to it to keep it up but it acts like its dieing please help i cant get mericle gro or plant food what els can i do to help it grow

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