Sexing Marijuana Plants – How to see if your cannabis plant is male or female

Sexing cannabis plants is vital for maximising your harvest. In this article, you’ll learn how to sex your marijuana plants (even before they flower), when flowering occurs, and how to induce flowering.

Sexing marijuana plants helps separating male from female plants. It only becomes possible to tell whether cannabis plants are male or female once the flowering cycle has begun. 

Cannabis begins to flower when it receives 12 hours of light and 12 hours of uninterrupted darkness in each 24-hour cycle.

Once this light cycle (or photoperiod) is initiated, plants enter the pre-flowering stage, when they increase in size as the branch structure prepares to bear and support flowers.

How to tell if your plant is male or female before flowering?

During pre-flowering, which usually lasts about 10 days, it is still not possible to identify the sex of the plant. The first flowers should be visible within two weeks.

Female cannabis plant

Male cannabis plant

Using feminized seeds or automatic seeds should eliminate this process as they are bred to produce plants that will flower as females.

Inducing flowering for sexing marijuana plants

Indoors, it is the grower who decides when to alter the photo period and induce flowering. This is achieved by simply adjusting the timers on the lights.

Outdoors, the grower must wait until the natural daylight hours have decreased to approximately 12 per day. Exactly when this occurs will of course vary depending on the locality. In Northern Europe it happens around mid-to-late July.

It is possible to induce flowering outside by allowing the plants 12 hours of daylight each day, then covering them or taking them inside.

This must however be done every day without fail. If the periods of darkness are interrupted by light, this can adversely affect the plants, setting it back to a vegetative state.

  • Disclaimer:
    Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.


5 thoughts on “Sexing Marijuana Plants – How to see if your cannabis plant is male or female”

  1. Hi! I starts one little seed the last week of January2021.. I live in Phoenix, Az. I planted the seedling in a small pot in my kitchen window on Jan. 30th and have not moved it. It does get 12 hrs of sun and so far it is only about 3 inches tall, but it is flowering. I can already tell that it’s a female. Am I doing everything ok? First time I’ve tried growing. Thank you and stay safe, healthy, calm and peaceful!

    1. Mark - Sensi Seeds

      Good afternoon Sonya,

      Unfortunately, legal restrictions mean we can’t answer grow-related questions or give grow advice on this blog. However, other readers of this blog will often answer questions like yours.

      Please check out the following articles on our blog which I think you may find of use, and I hope you continue to enjoy the blog!

      What are the best conditions for seedlings

      When can seedlings be put under lights or in the sun

      With best wishes,


  2. poi pakeha tipene

    Hi mine are all outdoors I’m in NZ I started from seed in October now they are about 4/5 meters tall now and I can’t tell if they male or female they get sun from about 8.30am till about 4.00pm how will I tell if they will show gender or should I wait till about April or May

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    Sensi Seeds

    The Sensi Seeds Editorial team has been built throughout our more than 30 years of existence. Our writers and editors include botanists, medical and legal experts as well as renown activists the world over including Lester Grinspoon, Micha Knodt, Robert Connell Clarke, Maurice Veldman, Sebastian Maríncolo, James Burton and Seshata.
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