By Dr. Daniela Vergara
Cannabis sativa is a fascinating plant for many reasons, but here we’ll continue focusing on how it reproduces. Cannabis sativa is part of a small group of flowering plants that have separate male and female individuals which are called dioecious.
This allows growers to produce seedless buds in unpollinated female plants, which tend to have higher levels of cannabinoids like THC and CBD, as well as more terpenes which are some of the compounds responsible for cannabis’s aroma and flavor. We’ve discussed this in previous posts.
Knowing how to tell male and female plants apart—and recognizing which varieties can produce one, the other, or both—is very important for growers. It helps them get better harvests and improve their plants over time.
In this article, I’ll explain the differences between male, female, and monoecious C. sativa plants (commonly called “hermaphrodites”).
Reproduction in Cannabis
Isn’t it interesting that plants can be male or female?
That’s one of the reasons I became interested in studying C. sativa back in 2013 when legalization began in Colorado. As an evolutionary biologist, I wanted to understand why sexual reproduction exists in natural plant populations, and we’ve been talking about this in previous blog posts where we discuss one of my latest publications (Baek and Vergara 2025).
Dioecious and Monoecious Cannabis
Most C. sativa plants are dioecious, meaning there are separate male and female plants. Only about 6% of all flowering plants (called angiosperms) are dioecious, which makes cannabis even more unique.
Some C. sativa are monoecious, which means one plant can produce both male and female flowers. People often call these “hermaphrodites,” but that’s not totally accurate:
- Hermaphrodite plants have both male and female parts in the same flower.
- Monoecious plants have separate male and female flowers on the same plant, but not in the same flower.
Male, Female, and Monoecious Cannabis Plants
As we mentioned in our previous post, male plants have XY chromosomes, just like human males and female plants have XX chromosomes, also like human females. Monoecious plants usually also have XX chromosomes, but we don’t yet know what parts of their DNA allow them to grow both kinds of flowers.
Male C. sativa Plants
Male plants make pollen, which they use to pollinate female plants. Their flowers have stamens and anthers, which are the male parts (called “staminate flowers”).
In C. sativa, pollen is spread by the wind, which is known as wind pollination or anemophily.
Female C. sativa Plants
Female C. sativa plants are the ones that produce buds—the part most used when cultivating marijuana-type varieties. These buds contain pistils, which are the female reproductive parts. Pistils can have multiple colors, such as white or orange or pink as in the picture, and stick out from the flower.
If a female plant is not pollinated by a male, it will grow seedless buds. These are known as sinsemilla (which means “without seeds” in Spanish) and are often higher in THC and CBD.
If the plant is pollinated, it will put its energy into making seeds instead of cannabinoids, which lowers the quality of the buds for most users.
We focus on female flowers because they have the highest concentration of trichomes—the tiny, hair-like organs where cannabinoids and terpenes are produced. While trichomes (from the Greek word for hair) are also present on leaves and male flowers, they are far more abundant on female flowers.
How to Tell if a Cannabis Plant Is Male or Female
Male and female C. sativa plants look the same when they’re seedlings or just starting to grow. You can usually tell them apart during the pre-flowering stage, a few weeks after growth begins.
- Female plants grow pistils with hair-like stigmas that stick out. These are usually white, pink, or purple.
- Male plants form small, round pollen sacs, often in clusters (resembling a tiny bunch of bananas) . These sacs are smooth, egg-shaped, or banana shaped. When they open, they release pollen that fertilizes female plants.
Flowers grow at the nodes, where branches meet the main stem.
Growers try to remove male plants early to prevent pollination, which can reduce the THC and CBD levels in female buds. Genetic testing you can often identify the plant’s sex before it fully flowers, as we discussed in our previous post.
Pollination Means Buds With Seeds
When a female plant gets pollinated, it produces a small dry fruit called an achene, which holds a single seed.
In marijuana farming, pollination is not wanted because it causes buds to form seeds, which lowers their quality. That’s why growers try to remove male and monoecious plants from their fields early.
Even though seeds are nutritious, no one wants to find them in a joint.
Can Marijuana Change Its Sex?
Yes. This is called sex reversal. Some growers use chemicals like colloidal silver or silver nitrate on female plants to make them grow male flowers and pollen. Or they use a chemical called ethephon on male plants to make them grow female flowers (check our previous post).
These chemicals affect ethylene, a plant hormone that controls growth and flowering.
Cannabis sativa can naturally grow flowers of the opposite sex, especially under stress (like changes in light or water). Because of this, cannabis is considered to have “plastic” or flexible sex expression.
A Quick Note on Feminized Seeds
As we mentioned in a previous post, feminized seeds come from female plants that were reversed to produce pollen. These seeds don’t have a Y chromosome, so they almost always grow into female plants.
- Most seed companies guarantee a 99.9% chance of producing female plants.
- Still, monoecious plants can sometimes appear.
- Feminized plants can also switch back and make male flowers if exposed to chemicals or stress.
Are Male and Monoecious Plants Ever Useful?
As we’ve mentioned, marijuana farming, the goal is to keep female flowers unpollinated. But in industrial hemp, pollination is wanted to produce hemp seeds for food and oil.
Male plants are important for breeding. They help develop new strains with unique traits. Monoecious plants can also be used in breeding since they make pollen too.
As mentioned earlier, pollen from genetic males is usually stronger and more vigorous than pollen from reversed females, which is often misshapen. Also, seeds made with male pollen tend to have higher germination rates than seeds from reversed females.
So, it’s possible that something in the Y chromosome of male plants helps produce better-quality pollen and stronger seeds. This makes genetic males especially valuable in breeding programs.
Because pollen spreads easily, growers must be very careful during breeding to avoid accidental pollination.
I hope you found the topic of sex in C. sativa as interesting as I do. Learning how genetics and the environment work together helps growers take advantage of the plant’s flexibility—and use these tools to improve their harvests.
References
Baek, Y. and D. Vergara. 2025. A review of sexual strategies in Cannabis sativa L. under genomic and environmental controls. Agrosystems, Geosciences & Environment 8:e70050.
