Plant Gender

Male and female cannabis flowers

Cannabis males flower producing small bell-shaped clusters, that hang down and open releasing the pollen, while females produce tear-shaped calyxes with two pistils – usually white – that group together forming what we call buds.

When to determine the sex of cannabis plants?

Male and female cannabis plants

Generally, cannabis plants start flowering when nights – dark periods – are longer, which is a sign to show their sex and start blooming. Actually, marijuana plants reach their sexual maturity between 6-8 weeks after seed germination , regardless of the photoperiod.

It is this fact what can help us to determine the sex of our marijuana plants without the need to make cuttings or change the photoperiod, what could strees our young plants.

As we mentioned before, when plants are about 2 months old – when they have 5 or 6 internodes – they are sexually mature, which is to say, they have set their sex. In some cases – most of them produced by stress – plants will show both sexes, being what we call hermaphrodites, but generally at this moment plants show their true sex, that will mantain for their entire life cycle.

This technique of premature detection of the sex needs a little practice, but once mastered it will allow us to determine the sex of our cannabis plants at a very early stage.

Early flowering of a female cannabis plant

Sexing cannabis from cuttings

If we can’t sex our plants with this technique, we can take a cutting from each of our marijuana plants and flower it in a growing tent – 12 hours of light/darkness photoperiod – what will force it to flower and show its sex, that will be exactly the same as its mother plant.

What we don’t recommend at all is forcing the flowering of mother plants for a few days/weeks and once they show their sex placing them again with a growing photoperiod (18 hours of light/6 hours of darkness), since this will produce major hormonal changes inside the plants, being an easy way to stress them – what will improve the chances to get hermaphrodite plants.

Male cannabis plant

What is a hermaphrodite cannabis plant?

Hermaphrodite cannabis plant

Hermaphrodite cannabis plants develop both male and female flowers. While it is a natural feature of the cannabis plant, it is an undesired trait when growing cannabis for consumption, since there is a great chance to obtain a plant full of seeds, what seriously reduces the quantity and quality of the final product.

Hermaphroditism can have 2 origins: genetic and environmental.

Genetically, some cannabis strains are more sensitive to hermaphroditism than others. This can be explained by the genetic origins of the strain – Thai sativas, for example, usually reach a high percentage of hermaphrodite plants – or also by the technique used when producing seeds (GA3,…).

Regardless its genetic sensitivity, a cannabis plant can also become hermaphrodite by the influence of stress. When it feels that the flowering conditions are too hard, hermaphroditism is an effective and natural way to shorten this period, pollinating its female flowers with the pollen of a few male clusters (usually called “bananas”).

Stress, that highly increases the risk of hermaphroditism, may have several causes, such as:

Changes in the photoperiod, specially interruptions of the dark period during flowering

Too much heat (>27°C aproximately), wrong environmental conditions

Harvesting too late, when the grower misses the deadline for harvesting his/her plants

Mechanical stress: broken branches, damaged roots, pruning during flowering,…

Irrigation issues (lack or excess)

Over-fertilisation

Insects, mites, diseases…

Thermal stress (irrigating plants with cold water…)

Use of phytotoxic products (pesticides, fungicides…)

To avoid hermaphrodite cannabis plants, the main rule is avoiding any kind of stress during their flowering period, so we limit the risks as far as possible. Pruning and staking of the plants should be performed during their growth and/or pre-flowering stage (stretch), before the buds start developing.

In order to lower the chances to get hermaphrodite plants, you should: maintain good environmental conditions in your growing space, a perfect hygiene, regularly monitor your timers , check your plants for insects and mites, water them regularly with a balanced nutrient solution. At the end of flowering, carefully check the trichomes so you don’t miss the harvest deadline.

When you have to decide which cannabis strains to grow on your next crops, carefully read any comments from other growers on the chosen strains, as well as seedbank advices and recommendations on them, so you have all the information about these seeds and can better avoid those strains with hermaphrodite traits in their gene pool. Actually, if there are too many comments about the hermaphroditism of a specific strain, the breeder him/herself often withdraws it from the market.

Regular cannabis seeds are known for being less sensitive to hermaphroditism than feminized seeds, although this is not an axiom, we must carefully chech our plants for male flowers whatever the type of seed we are growing.

What to do when we find hermaphrodite cannabis plants?

Cannabis hermaphroditism

As we mentioned before, it is very important to carefully check our plants for male flowers from the beginning of flowering. During the flowering period, these male flowers are easily observed due to their yellow colour and banana shape. We will also check for mites or insects, as well as molds, so we avoid the most common cannabis pests .

If a plant shows male and female flowers from the beginning of flowering, unfortunately we will have to eliminate it immediately from the growing space. Otherwise, it could pollinate the entire crop, transmitting the hermaphrodite trait to the offspring.

When the plant becomes hermaphrodite at full flowering, we have 2 options:

If the plant only produces few male flowers, we can remove them with a pair of tweezers (sterilized with alcohol), spraying water on them – water sterilizes pollen – and then watching for new bananas.

If the plant produces numerous male flowers, we should eliminate it from the growing space.

Finally, if a cannabis plant becomes hermaphrodite at the end of flowering, we should harvest it as soon as possible, before the male flowers release their pollen.

Detecting a hermaphrodite cannabis plant

Did you find seeds in your cannabis harvest?

Cannabis seeds developing

If you find seeds in your harvested buds and there is not any male plant near your growing spot, it is because there was at least one hermaphrodite plant in your crop. Those male flowers that were not removed released their pollen next to the female plants. Unfortunately, once pollinated the plant focuses its energy on producing seeds, instead of producing new flowers.

As we already mentioned, these seeds coming from hermaphrodite pollen will maintain this undesirable trait, so it is recommended not to grow them.