Cannabis Sex: What Determines It?

A male and female cannabis plant next to each other

Both genetics and environment play a role in the determination of the sex of a cannabis plant. Many growers focus on the growing conditions to ensure that hermaphroditism does not take place, but genetics play just as important a role.

A male cannabis plant
Male cannabis plant

Cannabis sativa L. is a dioecious plant – in other words, the male and female sexes are expressed in separate plants. With that being said, some cases of hermaphroditism are known to occur. The most desirable and psychoactive component of the plant is formed in the female flowers. Thus, knowing how to differentiate between male and female plants is integral to any grow operation, whether commercial or at home.

Male cannabis plants have their purpose, too. Even if the buds are not harvested for sale or consumption, male plants are imperative to a breeding program. For this reason, growers and breeders must know the differences between male and female plants and what determines this, especially to avoid hermaphroditism.

Which factors influence the sex of a cannabis plant?

How and why the sex of cannabis plants is determined is a subject frequently discussed by cannabis growers all over the world.

A pink female figure and a blue male figure

The determination of gender in human beings is simple: the male, who possesses both X and Y chromosomes, either gives or does not give a Y chromosome to the embryo. If it does, the child is born a male. If it does not, the child is born female. However, recent studies have shown that under stressful conditions, the male is more likely to produce spermatozoa containing X chromosomes.

In human embryos, a single X chromosome and a single Y chromosome denote a male (XY). Two X chromosomes denote a female (XX). The combination of genetics from egg and sperm create a diploid cell, containing two chromosomes.

Haploid cell, diploid cell, triploid cell and tetraploid cell

In the case of cannabis, things are a little more complicated. While cannabis has been identified as having diploid cells, there are researchers producing tetraploid plants of cannabis for the purpose of improving its medical qualities. Tetraploid cells contain four chromosomes of either X or Y (XXXX, XXXY, XXYY, XYYY or YYYY). However, it is unlikely that tetraploidy occurs in cannabis in nature.

Generally speaking, in mammals, sex is determined at birth, with no interference on physical sex by developmental conditions. For example, even under stressful circumstances, a female reproductive organ won’t turn into a male reproductive organ. However, this does occur in cannabis. Therefore, the genetic make-up of the seed cannot be the sole factor involved in determining the sex of marijuana plants.

It is for this reason that some cannabis growers place more importance on growing conditions. Under extreme or poor growing conditions, there is a predominance of male plants. This is not so farfetched, as the main objective of a cannabis plant is to procreate.

Essentially, for a male plant to grow under adverse conditions is a defense mechanism of the cannabis plant, as one male can pollinate hundreds of female plants. The effect of growing conditions on both male and female plants will be discussed later in the article.

So as the understanding of cannabis cultivation has it, both nature (genetics) and nurture (growing conditions) influence the sex of the cannabis plant. But how exactly does this work?

1. Nature: The role of seed genetics

As much as growing conditions play a vital role in determining the sex of cannabis plants, there is also plenty of genetic information stored in seeds. In the presence of optimum growing conditions, it is the seed genetics which will determine the sex of the plant.

Botanists and researchers of this 2004 study identify fragments of gene sequencing that determine the sex for both male and female plants. They also identified certain gene fragments which may play a role in the development of hermaphrodite plants. In any case, the results of this study show that the genetics of a plant play a role in determining the sex. The commitment to a specific sex takes place as soon as the leaves of the fourth node emerge.

Remember, this is different to determining the sex of a plant as a grower. Cultivators do not need genetic identification material to understand if their plants are male or female. Rather, certain signs in early plant life can be used by a grower to help them determine the sex of their plant.

2. Nurture: Growing conditions and feminisation

A female cannabis plant
Female cannabis plant

The feminisation of cannabis seeds is a perfect example of how cultivation conditions are also intrinsically linked to a plant’s final sex. Feminisation consists of taking a female plant and turning into a hermaphrodite by creating environmental stressors. At this point, certain female flowers will begin to produce pollen, which can then be used to pollinate the same plant. The final product is a feminized seed.

Which external factors can affect which sex the cannabis plant manifests?

  • Stress

In general, plants that are subjected to stress around 3 weeks into vegetation are more likely to manifest male genetics. If stress takes place later on in vegetation or during flowering, a plant may be forced into hermaphroditism.

  • High humidity

When humidity exceeds the optimum amount for cannabis, it is more likely that male plants will develop. In conditions with less relative humidity, it is more likely that female plants will develop.

  • Soil moisture

Interestingly, the moisture of the soil is another environmental condition that can affect the sex of a cannabis plant. In soil that contains too little moisture, it is more likely that a male plant will develop.

  • Temperature

The warmer the environment, the more likely it is that a male plant will develop. However, with that being said, it is possible that this stressor is linked with the photoperiod. In warmer climates, there are generally longer days and shorter nights, and the effect of temperature is inextricably linked with photoperiod.

  • Light spectrum

In indoor cultivation programs, the grower may choose the colour of the light spectrum. The more blue light appears in the spectrum, the more likely that female plants will develop.

  • Photoperiod

Finally, photoperiod is an important environmental condition that can affect sex. Shorter light hours per day usually results in more female plants, while longer exposure to light usually results in more male plants.

Ultimately, any grower can force a developed female plant into being a hermaphrodite by adjusting the environment. Changes in photoperiod, increasing the temperature, harvesting too late or over-fertilizing may all result in a female plant turning into a hermaphrodite. With that said, hermaphroditism may also occur as a result of genetics, as some strains are more prone to hermaphroditism than others.

When plants are kept in the correct optimum environment for their genetics, there is generally a small likelihood of hermaphroditism unless the seed is genetically prone. This is why growers must pay close attention to the cultivation environment to avoid hermaphroditism.

Long story short: As almost always, it’s not nature and nurture. A combination of both genetics and environment play a role in the determination of the sex of a cannabis plant.

  • 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.

Comments

11 thoughts on “Cannabis Sex: What Determines It?”

  1. Johhny Appleseed

    well lets be truthfull here. I have not heard one person talk about dominant, recessive or co dominant traits. There are roughly 38 000 Genes from what I have read, this may not be accurate. So if the male holds a recessive trait on the X chromosome and the mother also holds one what happens then. What happens if the trait you are looking for is on the Y chromosome. Then that trait can never be able to pass on that trait to a female offspring. In Reality the Y chromosome of the offsprings son has the same DNA as his fathers DNA and his fathers and so on. Only a male plant can be traced back to his father as each son can only get his MALE characteristics from his fathers Y. Untill we know exactly what traits are dominant, recessive, co dominant we will never really be able to stabilize a poly hybrid. Sure we may stabilize a few traits but never we will be able to have the same true breeding strains as the land races we all started from. Those were inbred for thousands of years. Now we a mix match of plants much like humans. 7 Billion people on planet Earth and maybe you have 5 dopplegangers.

  2. Anne Westrup

    i am no scientist so this observation may be way off base, but it seems in stressful situations, the females would HAVE to survive at higher rates in order for the species to survive. Given that ONE male can pollinate hundreds of females that would make more sense. that is, a higher survival rate of female plants. the male plays a very small role really (yes, it’s important, but….) – kinda like humans. The only thing the man does is ejaculate, then he is of no further use – in terms of reproduction, the biology of it. If every man on earth died today, life would continue – we have frozen sperm and uteruses (sp?). If all females died today, humans would be extinct within one generation. (i guess that didn’t need to be said, but i get a kick out of it – i’m no man hater, it’s just fun to watch their faces as they absorb that little tidbit, totallly emasculated in under 10 seconds.
    Anyway, is there anything to my theory that female plants would have to survive in higher numbers in order for the species to survive? plus their role is much more important in terms of the end product. That’s only a bonus for pot users. The plant’s motivation is survival. The species’ survival doesn’t REQUIRE many males – in fact might survive without any males at all. or rather “original” or “born” males. The grower could perform a sex change on one or two females – at least from what i read in the article it seems possible, plausible. One human male could get 20,30,40, 50 women pregnant within a week,(at the same time basically) can you imagine having 40 women pregnant AT you? That scenario is also humorous. just having fun.

    1. Mark - Sensi Seeds

      Good afternoon Anne,

      Thank you for your comment.

      In the wild, if there are male plants in close proximity, pollen will travel through the air pollenating the female. If the female plant isn’t pollinized, seedless flowers, often referred to as “sinsemilla” will continue to develop .

      Strains that reproduce through pollination out in the open, where males get mixed with many females often leads to hermaphroditism. If the female is pollinized by a different pollen grain, which does not necessarily have to be of the same male, genetic variability can be very high and unstable. As a result of inbreeding, the majority of off-spring will be hermaphrodite or hermaphrodite monoecious

      Ultimately, any grower can force a developed female plant into being a hermaphrodite by adjusting the environment. It may also occur as a result of genetics, as some strains are more prone to hermaphroditism than others.

      In terms of whether the female plant is stronger than the male. It completely depends on the genetic background, and the environment.

      Male cannabis plants pass genes on to their offspring. These traits may include resistance to pests and mould, adaptation to different climates, successful growth rates, and general health. As such, males are essential pollen producers that play an integral role in cannabis breeding.

      This article on Male Cannabis Plants: 7 Things to do With Males might also be of interest to you.

      Thanks again, and have a great day!

      Mark

  3. I was told I bought a clone of a female plant, however my sister who grows saiid it looks male.
    If I take a picture would anyone be able to identify its gender?
    First time grower!

  4. question? when breeding for environmental condition, ie crossing sativa with indica in order to favour a northern environment, does the potency of the offspring depend upon the male, or female contributor?

    1. Scarlet Palmer - Sensi Seeds

      Hi Ken,

      Thanks for your question. From my knowledge of breeding, it is usually the mother that passes on the dominant characteristics. I’m not sure if you mean potency as in strength of effect, or potency as in resistance to cold climates, but either way the resulting offspring will inherit more of their mother’s traits.

      With best wishes,

      Scarlet

  5. Interesting discussion Stephanie, a few observations made over twenty years experience in agriculture has led me to add to your conclusions. Hermaphrodism is rare in cultivated and conscientious growers gardens, who’s prime goal is quality of bud. However the growers that prime goal is resin production the resultant genetic and seed quality control is sadly lacking. An example of volume versus quality. The contentious part comes when bud growers gardens are compromised by hash growers pollen. I have seen strains which are 90% hermaphrodite, strains which are 90% female and thanks Sensi last year 75% male.

    In conclusion the greatest influence is the seed producers knowledge, experience and conscientiousness. Stress as we all know forces survival and there will always be exceptions to the rule.

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    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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