How to Tell When Cannabis Plant is Flowering

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Added 19 August 2020

How to Tell When Cannabis Plant is Flowering

How Do I Tell if My Cannabis Plant is Flowering?

As you switch your plant's light schedule and it begins to flower, you will likely be waiting eagerly for those first buds to appear. It is an amazing process to watch a plant develop its flowers but we must also be monitoring it carefully through its life to make sure we finish with a tasty smoke. You could end up with results like this:

NuggetPawn's recent harvest on GrowDiaries of Royal Gorilla (Royal Queen Seeds)

The main reason we check cannabis plants for their flowers is to avoid problems with male flowers. For some growers it is intentional to grow them as a way to create new strains or produce seeds, but for most it can be a real pain. A male genetic in your garden will pollinate the females fast if it is not sorted out. This is why so many growers love feminized seeds.

You may be asking yourself, 'But how do I tell if my cannabis plant is flowering?' Look no further, as we are here to go through all the things to watch out for when checking your plants for flowers. With just a few precautions you can save yourself a lot of time and hassle. To make the process easier for you, we have created this simple guide.

Female Cannabis Flower Growing Pistils

Buds by BodyByVio from GrowDiaries at around 6 weeks of flower. Check those pistils.

The Difference Between Male and Female Flowers

Male cannabis flowers look very different to female cannabis flowers. The key is to spot them early so you can act quickly.

Whether you are growing regular seeds, autos or feminized seeds, a plant will show its sex after about 3 weeks of being in vegetation, although some strains may take a bit longer. During this stage we can check the preflowers for any early signs of sex. This grower noticed his plants were male after flipping them into flower, so be careful.

Check it out here:

The preflowers are a sign that the plants are nearly ready to enter their flowering stage. Until now the plant will have grown branches and leaves opposite each other from the main stem, however at this point they will start to alternate.

Female Cannabis Flower

Female flowers developing pistils.

We can identify a cannabis plant's flower by checking for these characteristics:

  • A male preflower is a very small closed ball or sac that is full of pollen. This will eventually bloom during the flowering phase and spread it's pollen over far distances to try to mate with a female.
  • Female flowers show their sex a week or two after males, at around 4-6 weeks from seed. They look like tiny, tear drop shaped buds (calyxes) with white pistil hairs. These pistil hairs are called stigma. If a plant is female, these will grow in large numbers around the internode areas as the plant flowers, to eventually form what we normally call 'bud'.

Difference between male and female flower.

The difference between a male and female flower.

Both male and female flowers grow near the leaf internodes on the branches. This is the best place to check because between the leaves they are not easy to see.

Note: The tiny, pointy leaves which also grow near the internodes are not to be mistaken for preflowers. These are called stipules and are related to the leaf structure of the plant, not the flowers.


Growers can expect different results depending on the kinds of seeds they are growing. Regular seeds usually produce approximately half male plants and half female plants. If you received feminized seeds then it is very unlikely you will end up with male flowers but it can still happen if a plant becomes stressed. A female plant that produces male flowers is what is called a hermaphrodite or 'hermie'.

Hermaphrodite Preflower

A hermaphrodite plant.

Light leaks, sudden temperature changes, deficiencies and other stresses can cause female cannabis plants to turn hermaphrodite. This means that they will produce both male and female flowers. Your buds will have seeds in them and this is not favourable if you are looking for a smokable product. Preflowers of a 'hermie' look like a small yellow banana and are often found growing near bud sites.

Hermaphrodite 'Banana' Flower

Early Signs of Flowering

Your plants will start their flowering cycle after you change your light cycle from 18/6 to 12/12. Within the first week the plants should start to show their pistils in larger numbers. If you are growing feminized seeds, this is the best time to check for hermaphrodites.

As the plant grows and buds develop, it becomes harder to spot male flowers. After the first few days of flowering you should be checking for male flowers. If you notice them early you will avoid ruining your hard work later on.

Male Sacs Spreading Pollen

To tell if you have male flowers growing on your plants, you will need to check them one by one. If you have found signs of male flowers on a single plant in a crop, remove it from the grow space immediately. It is recommended you discard it as soon as possible so that it cannot spread it's pollen. You must then check the other plants daily to make sure the pollen has not spread and that male flowers have not started developing on other plants.

  Male Female Hermaphrodite
Pollen Sacs X    
Calyxes with Pistils   X  
Pollen Sacs and Calyxes with Pistils     X

Catching males early so that you can remove them before the 'buds' open is essential. If you don't, you could likely end up with seeds across your whole garden.

Male Cannabis Preflower

Here is a checklist of 5 things you should be doing when checking your plants for flowers:

  • Remove a plant from the grow space. If this is not possible then check them in a logical order (e.g. left to right).
  • Start to work your way down each branch, checking every internode. Male flowers will normally start to grow first on the upper leaf internodes of a branch. 
  • Throw away any plants showing signs of male flowers, unless you want to keep them for other purposes.
  • Do not try to stop pollination by removing the male flowers or 'bananas'.
  • Monitor plants and check daily for signs of new male flowers in your garden.

Bud with Seeds


After reading this you have learnt how to identify the gender of a plant as it reaches it's flowering phase. It can be a bit of a daunting task especially if you have a lot of plants, but we highly recommend spending time making sure your garden is producing as you want it to. If you do find male flowers in your garden, don't panic. Come back to this guide, and if you have any questions, leave us a comment below.

External references

  1. New Insights on Flowering of Cannabis Sativa. - S. Duchin, N. Bernstein, R. Kamenetsky, B. Spitzer-Rimon
  2. Chemical Characterization of Leaves, Male and Female Flowers from Spontaneous Cannabis (Cannabis sativa L.) Growing in Hungary. - David U. Nagy, K. Cianfaglione, F. Maggi. (2018)

This article was updated August 2020.


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