How to distinguish male and female marijuana: Differences and Similarities

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Learn how to identify male and female marijuana

Marijuana is a captivating plant for many reasons, but today we will focus on its reproductive strategy. Cannabis sativa is one of a small group of flowering plants that has both male and female individuals, that is, it is a dioecious plant. This dioecious characteristic of marijuana allows the generation of seedless buds with the potential to produce high concentrations of terpenes and cannabinoids such as CBD and THC.

Differentiating female plants from males and varieties that can produce one, the other or both sexes has been essential for growers and breeders to increase the yield of their grass crops and improve their varieties. In this post I explain the differences and how to distinguish male, female and monoecious (commonly known as hermaphrodite) marijuana plants.

Marijuana sexual reproduction: Why are there males and females?

Isn’t it curious that there are male and female cannabis plants?

Well, I’m going to start by telling you that the fact that the plant Cannabis sativa presents males, females and monoecious individuals was what most caught my attention to study it during the time of marijuana legalization in Colorado, in 2013. My background as an evolutionary biologist and my PhD thesis is based on understanding why sexual reproduction exists in natural populations.

Marijuana: a dioecious and monoecious plant

Marijuana is a dioecious plant, which means that it has specimens with male flowers and other specimens with female flowers. Only 6% of flowering plants, called angiosperms, show this type of sexual expression, including cannabis(Cannabis sativa L.) [1,2]. The fact that marijuana is part of this minority of dioecious plants makes it even more intriguing.

Marijuana has male and female individuals, which in biology is called a dioecious plant. Only a minority (6%) of flowering plants (angiosperms) are dioecious.

Now, marijuana plants (and hemp plants) also have monoecious individuals, which are those that produce both male and female flowers on the same plant. Although colloquially they are called hermaphrodites, this denomination is not correct, because hermaphrodite plants are those that have male and female reproductive organs in the same flower, while monoecious plants have male and female flowers in the same plant, but not necessarily in the same flower.

Differences between male and female marijuana: How to distinguish them?

What is male marijuana?

Male marijuana plants are those whose flower produces pollen, and these are characterized by the presence of stamens and anthers (called male or staminate flowers). Cannabis pollen is dispersed by the wind to pollinate female plants (anemophilous pollination).

Male marijuana flowers (illustration)
Male marijuana flowers, with botanical illustration. Credit: Dr. Vergara

How is female marijuana different?

On the other hand, female marijuana plants are those that produce flowers with female organs, such as the pistil, where the stigmas are, which in marijuana can vary in color (female or pistillate flowers).

Flowers marijuana female botanical illustration
Female marijuana flowers with botanical illustration. Credit: Dr. Vergara

What is monoic marijuana?

Monoecious cannabis plants produce both male and female flowers on the same plant, i.e. they produce both pollen and pistils with stigmas. These plants can self-fertilize and produce buds with seeds, as well as pollinate other female plants around them. In a marijuana crop, monoecious plants are eliminated as if they were male plants.

Apparently, according to anecdotes, these plants can also produce hermaphrodite flowers, called “platanitos“, “bananas” or “nanners“. Instead of producing male flowers, they only develop a stamen without sepals inside the female flower. This exposed stamen deposits pollen directly on the buds, allowing self-fertilization and ensuring successful pollination.

The monoecious phenotype, like all phenotypes, has a genetic basis and some hemp plants are always monoecious, but this phenotype can also be caused by environmental influences, such as photoperiods and hormones among other environmental conditions.

Monoecious marijuana
Monoecious marijuana. Credit: Dr. Daniela Vergara

Marijuana pollination: buds with seeds!

The flower of the female marijuana plant contains the largest amount of trichomes. trichomes (Greek for “hair”), small structures where cannabinoids such as CBD and THC are produced and concentrated. This is why, when we consume cannabis, the flower of the female plant is used, also known as the flower of the female plant. marijuana buds .

When a female plant is pollinated, it produces a type of dry fruit called achene, which contains a single seed inside: this is what we know as a hemp seed .

Hemp seeds
Hemp seeds

In marijuana crops, pollination of flowers is not desirable because buds with seeds would come out. Therefore, work is being done to detect and eliminate male and monoecious plants.

Although hemp seeds have many nutritional properties, no one likes to find them in their joint. Therefore, in smoking herb crops it is a common task to detect male and monoecious specimens in order to eliminate them and thus prevent pollination.

In reality, although marijuana can produce seeds, it is not grown for seeds or hemp oil, because its yield is low. For such uses, cannabis varieties with high seed production (grain hemp) are used. For more information, see the post on the differences between hemp and marijuana .

Utility of male and monoecious marijuana plants

In a marijuana crop, it is always tried to avoid male and monoecious plants, since it is sought that the flowers of the female plant are not fertilized and thus produce more compounds, such as cannabinoids and terpenes (these apparently decrease when there is pollination). But also, because nobody wants seeds in their joints, a commercial reason why the pollination of female marijuana is avoided by removing the male plants from the crops.

Something very different happens in industrial hemp plantations (of the same species Cannabis sativa), where pollination is sought in order to obtain seeds that are then used for the production of food and oil.

Male marijuana plants are required to generate new crosses with different characteristics.

But be careful, when you are looking to improve or produce new varieties, males are necessary, and suddenly also monoecious marijuana plants, in order to obtain pollen for new crosses. It is necessary to be very cautious when working with pollen, to only pollinate the required plants and not others.

How to distinguish male from female marijuana

Male and female cannabis plants appear identical during the seedling and early vegetative growth phases, but begin to distinguish themselves as they progress through the flowering phase.

The differences between male and female marijuana are in their flowers. Both the female and the male develop at the nodes of the plant (where the branches join the main stem), and to distinguish them, they must be carefully observed. Thus, we can differentiate between male and female flower structures:

  • Female marijuana plants show their sexual characteristics in the form of thin, elongated, white or purple stigmas.
  • Male marijuana plants have no stigmas and instead grow small, often clustered pollen sacs. When these sacs open, they spill their contents and pollinate the female plants, which could apparently decrease cannabinoid production due to pollination. If you have a marijuana crop, you should not let these plants get to that point. Fortunately, it is possible to differentiate male from female plants when the flowers are still immature and by genetic testing before they flower.

When is it possible to differentiate between male and female marijuana?

Some people can tell the difference between female and male plants in early flowering. Pre-flowers are the initial stage of flower development. Their differentiation does not occur until after a few weeks, when they show their male or female features and can be clearly differentiated.

The male preflowers can be distinguished by their shape, similar to small eggs, more spherical than the female flowers, and which, observed with a magnifying glass, are completely smooth, without hairs or trichomes.

There are also some who say that the distance between the stem nodes of the males is wider than in the females, and that for this reason they can be differentiated even before flowering, but these are anecdotes without scientific support.

Why are there male, female and monoecious marijuana plants?

The reason why some plants such as marijuana have male, female and monoecious specimens is still unknown, but there are many scientific hypotheses that try to explain it. But what we do know is that, like humans, male marijuana plants have a Y chromosome, i.e., they are XY. Also, like humans, female cannabis plants have two X chromosomes, i.e. XX.

Monoecious plants appear to have very similar chromosomes to females, XX, and the regions of the genome (of plant DNA) that allow monoecious plants to produce both male and female flowers are not yet known.

Does marijuana change sex?

Now, to make matters more complex, you may have heard of, or practiced it yourself,sex reversal. This is when chemical compounds such as silver nitrate or colloidal silver are used on females to produce male flowers and pollen, or ethephon is used on males to produce female flowers. These compounds modulate ethylene, an important hormone in plant growth and development [3], by inhibiting it [4] or stimulating it [5].

Cannabis plants can produce flowers of the other sex, and this can be induced by using feminizing or masculinizing agents.

The sex-reversal technique has been used by cannabis breeders and breeders to self-fertilize plants with desirable characteristics. This is why Cannabis sativa could be considered as a plant exhibiting plastic or inconsistent sexual expression. (plastic sex expression “leaky” or “inconsistent”.The reason for this is the possibility of reversing the sex with feminizing or masculinizing agents [6, 7] and also because males and females sometimes produce flowers of the opposite sex [8].

Feminized seeds: trying to ensure female cannabis plants

As I told you above, the sex of Cannabis sativa plants can be reversed, using chemical agents or even some varieties express flowers of the opposite sex when under stress, or due to light or water changes. When a female plant is fertilized with its own pollen, or with pollen from a female that was subjected to sexual reversion and produced pollen, the seeds do not have a Y chromosome (the chromosome of male plants). These seeds are commercially known as feminized seeds.

Feminized seeds lack the Y chromosome, so the plants have a minimal chance of producing pollen.

Feminized seeds have a high probability of growing as female marijuana plants. Most feminized marijuana seed banks offer a 99.9% guarantee of producing buds.

Two things: First, these feminized seeds usually produce only females, but occasionally males and monoecious are found. Second, these feminized plants can also be sex-reversed with chemical agents or when under stress, and produce male flowers and pollen.

Unknowns to be investigated on the sexual expression of cannabis

Many questions arise from the possibility of sexual reversion: For example, where are these genes that are “turned on” or “turned off” when there is sexual reversion? Will these genes be on the sex chromosomes, or in other parts of the genome? Why are some marijuana strains more prone to sexual reversion than others? Do they differ in the type of genes, or do they have the same genes and differ in their expression? How much do genes control sexual expression, and how much does the environment play a role? Why is there this possibility of sexual reversal or this plastic or inconsistent expression? Will it have any adaptive advantage? … And well, I could fill this paper with more and more questions!

I hope you found the sexual determination and expression of Cannabis sativa as interesting as I did. Understanding how the various factors interact may allow growers to take advantage of the flexibility of this species to modify its sexual expression. And by using these techniques, provide more efficient methods for farmers to obtain a good harvest.

Referencias

Charlesworth, D., What maintains male-sterility factors in plant populations? Heredity, 2002. 89(6).

Renner, S.S. and R.E. Ricklefs, Dioecy and its correlates in the flowering plants. American journal of botany, 1995. 82(5): p. 596-606.

3. Ecker, J.R., The ethylene signal transduction pathway in plants. Science, 1995: p. 667-675.

Kumar, V., G. Parvatam, and G.A. Ravishankar, AgNO3: a potential regulator of ethylene activity and plant growth modulator. Electronic Journal of Biotechnology, 2009. 12(2): p. 8-9.

Yamasaki, S., N. Fujii, and H. Takahashi, Characterization of ethylene effects on sex determination in cucumber plants. Sexual Plant Reproduction, 2003. 16(3): p. 103-111.

6. Moliterni, V.M.C., et al., The sexual differentiation of Cannabis sativa L.: a morphological and molecular study. Euphytica, 2004. 140(1-2): p. 95-106.

7. Truta, E., et al., Some aspects of sex determinism in hemp. Analele Stiintifice ale Universitatii” Alexandru Ioan Cuza” din Iasi Sec. II a. Genetica si Biologie Moleculara, 2007. 8(2).

8. Pannell, J.R., Plant sex determination. Current Biology, 2017. 27(5): p. R191-R197.

9. Mandolino, G., et al., Identification of DNA markers linked to the male sex in dioecious hemp (Cannabis sativa L.). Theoretical and applied genetics, 1999. 98(1): p. 86-92.

10. Törjék, O., et al., Novel male-specific molecular markers (MADC5, MADC6) in hemp. Euphytica, 2002. 127(2): p. 209-218.

Information about male marijuana (frequently asked questions)

What is male marijuana used for?

Why do males exist is a question that Charles Darwin himself asked in his book “The Origin of Species”, and it is one of the most beautiful questions in evolutionary biology. The short explanation is that males serve to provide genetic variation in populations. Thus, male marijuana serves to fertilize females to produce diverse progeny.

What is female marijuana used for?

It is from the female marijuana that the cannabis flower is obtained, the part of the plant that contains the trichomes, which are organs where cannabinoid compounds such as THC or CBD are produced. It is what we popularly call marijuana buds. What we smoke, or what is processed to produce CBD candy, cookies, brownies etc. is the flower of the female plant.

When can the sex of marijuana be detected?

Determining the sex of marijuana with the naked eye occurs during the flowering of the plant. The detection of male plants at an early stage, when they are still seedlings, is possible by means of genetic testing. Currently there are several DNA tests to know if the plant is going to be male from an early age. These tests consist of determining the presence of the Y (male) chromosome. There are several companies that provide this service, using genetic markers [9, 10]. Now, these markers do not give information about monoecious plants, or about the possibility that the plant can produce male flowers under stress or under sexual reversion.

Is it possible to buy female marijuana seeds?

Of course! What’s more, there are many breeding companies that have made these feminized seeds their flagship brand.

Can you tell if a marijuana is male by the seeds?

Technically yes, but it is quite complex. You would be able to tell if the marijuana plant is male with a DNA extraction, and this is very difficult to do with seeds. There are other plants, such as corn, for example, from which it is easier to extract DNA from their seeds, but in Cannabis sativa it is quite difficult. Therefore, it is most common to detect male marijuana plants when they begin to develop their flowers.

What happens if a marijuana plant is male?

If you discover that you have a male marijuana plant in your crop and you do not plan to breed, it is best to remove it from the crop to prevent it from pollinating the females. As with monoecious plants, they should be culled.

What is smoked from male marijuana?

Male marijuana plants are not usually smoked because they contain hardly any cannabinoids. However, if the plant has a good size or characteristics that interest us, we could use them to make crosses with the best specimens of female marijuana and thus try to get varieties with the desired characteristics.

What happens if you smoke a male plant?

Male marijuana plants may look intriguing, but they are best left alone. If you smoke male marijuana you will probably not feel any effect due to the low cannabinoid content. In addition, compared to female marijuana buds, male marijuana plants contain very low levels of terpenes, so their odor and aroma will be lower. Male plants produce a lot of pollen when mature, and many people are allergic to it.

What is the difference between male and female marijuana?

Male marijuana plants are discovered through small balls that are born in the axils of the leaves or branches, which are the male flowers and produce pollen at maturity. In contrast, female plants have pistils with stigmas that can vary in color, resembling small hairs.

What is male marijuana called?

I call them Pedro or Juan, but I have also heard of Camilo and Sebastián.

How to avoid crossing male and female marijuana plants?

Outcrossing can be avoided by detecting male plants in time and eliminating them from the crop so that they do not pollinate female plants.

What is hermaphrodite marijuana?

Actually, there are no hermaphrodite marijuana plants, at least that I know of, where the same flower has both male and female organs. There are monoecious Cannabis sativa plants, where the plant has both male and female flowers.

How does monoecious marijuana come out?

In some varieties, monoecious traits can appear at any time, even in feminized seeds, and is caused by environmental stressors such as lack of water, nutrients or light changes.

How do you know if marijuana has been pollinated?

Look at the marijuana flower and see if the bracts have enlarged: these small leaf-shaped structures protect the reproductive organs of female marijuana plants. If you suspect pollination, use tweezers to open the bracts. If a seed is found inside, it is a sign that pollination has taken place.

How do seeds form in marijuana buds?

If you discover seeds in your weed bud, what has happened is that the crop where the weed came from had a male plant around it, or a female plant that, under stress (or other factors), has started to produce pollen. Marijuana pollen can travel by wind and pollinate female flowers, which then produce buds with seeds. The marijuana plant reproduces by seeds, which are the product of fertilization by pollination of female plants. The male flowers produce the pollen necessary for sexual reproduction, which travels by wind to the pistil of the females, fertilizing them. This produces the achene, a single-seeded nut, which is what we know as hemp seed.

Are there self-fertile cannabis plants?

Yes, apparently the Cannabis sativa plant can self-fertilize, when it is monoecious or when there is sexual reversion. Now, apparently, these self-fertilized plants in some generations degrade, which is called in biology as inbreeding depression.

Dra. Daniela Vergara
Investigadora y catedrática | Especialista en cultivos emergentes y consultora de cannabis

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