Plant reproduction is an interesting and surprisingly complex field. Some plants are dioecious, meaning they produce one of two different types of flowers (male or female). Others are monoecious, meaning they grow single flowers with male and female reproductive organs (also known as hermaphrodites).
Cannabis plants are generally dioecious. Each plant usually features either male or female organs. They don’t usually have both. There are some circumstances that can lead to female plants becoming hermaphrodites, but more about that later. For now, growers just need to know that cannabis plants can be either male or female, and it’s important to know the difference.
Those who are completely new to growing cannabis may be asking themselves why they need to concern themselves with the reproductive organs of their plants. There’s a simple and very compelling reason for it: only female plants produce good marijuana buds, and female plants can only grow in the absence of males and hermaphrodites in order to produce the seedless, resinous buds that marijuana connoisseurs across the world have come to know and love.
The only circumstance under which it’s a good idea to have male plants interspersed in a marijuana crop is if growers plan to save seeds for the next year’s crop. Only experienced growers with a background in plant propagation and identifying desirable traits should go this route. Most are better off purchasing new seeds each year. Buying only feminized seeds will also help guarantee the success of your crop, but again more about this later.
The best way to identify the gender of a naturally grown cannabis plant is to take a look at what is growing between its nodes. The growth nodes can be found between the stalk and stems. At first, they develop similarly in male and female plants, but by the end of the vegetative stage, the difference between them makes itself clear.
Female plants develop reproductive organs known as stigmas, designed to catch pollen. Male plants, on the other hand, develop pollen sacs. These organs should be developed enough to identify at between four and six weeks into the vegetative phase.
Female plants first develop two bracts. They look a little like the pollen sacs on male plants, so don’t be too quick to pull them out as soon as they develop. Female pre-flowers will develop long, translucent hairs, known as pistols. They may not be visible to the naked eye early on in the pre-flowering stage, so feel free to use a magnifying glass to get a closer look.
Male pollen sacs don’t have stigmas, the translucent hairs found on female plants. Instead, their pollen sacs just look like tiny balls of plant matter. They may be round or slightly ovular.
The most reliable method for sexing plants is waiting until the pre-flowering stage and checking for pollen sacs or stigma. However, there are a few other noteworthy differences between male and female cannabis plants. Male plants have thicker, sturdier stalks, which is what makes them so useful in producing textiles.
The biological reason that male plants have sturdier stalks is that they also grow taller than their female counterparts. They need sturdy stalks to support their own weight. Female plants also have more leaves than male plants. The leaves may also have a slightly different shape with a fuller body, but every strain of marijuana has slightly different leaves, so this isn’t a reliable way to tell the sex of the plant.
Some plants grow both male and female reproductive organs. These are known as hermaphrodite plants. Since they produce pollen sacs, which can pollinate other female plants, it’s important to treat them like males and remove them as soon as they appear.
There are two main origins of hermaphroditism in cannabis plants: genetics and the growing environment. Some strains are more prone to hermaphroditism than others, but even strains that are not prone to this natural phenomenon can still become hermaphrodites under the wrong growing conditions.
The primary environmental factor that causes hermaphroditism in cannabis plants is stress. While some forms of stress are good for female plants, such as those used to induce heavier flowering, too much stress is never a good thing. Avoid excessive heat, sudden interruptions in the photoperiod during the flowering stages, irrigation issues, overfertilization, and excessive mechanical stress (i.e. repotting) during flowering, as these can all contribute to hermaphroditism.
The fact that female plants can develop male reproductive organs even during the flowering stage when exposed to severe stress means that growers should check their plants periodically for pollen sac growth, even if they’re sure they’ve already pulled out all the male plants. Just one hermaphrodite plant can pollinate not just itself, but also the other female plants around it, effectively ruining an entire crop.
Without male plants, female plants are unable to produce seeds. That’s a problem for growers who want to save seeds for the next year’s crops, but it’s good news for those who want to produce high-quality marijuana. Seeded buds are less potent, less tasty, and harsher on the throat than the high-quality, unseeded marijuana produced by commercial growers.
Those who want to save seeds for the next harvest period should still remove the male and hermaphrodite plants from their commercial crops. They can set up separate grow rooms or gardens for plant propagation. Just make sure to locate the seed-producing plants as far away as possible from the marijuana crop to avoid unwanted pollination. Distance alone will not keep your females safe, as pollen has been known to travel up to 10-30 miles. To be safe use a separate grow tent or sealed room to prevent cross-pollination.
Unless they want seeds for the next season and have already created dedicated space for pollinated plants, growers should remove and destroy their male and hermaphrodite plants immediately after sexing them. Remove the entire plant, roots and all, instead of trying to remove each bud by hand. Just one missed pollen sac can pollinate an entire crop of female plants.
After removing the plants, take care to dispose of them far from the crop. Growers who live in cities or suburban areas can simply toss them in the garbage or yard waste. Those who live in the woods may want to compost their male plants, but they should only do so if they are certain that the compost pile is far enough away from the female plants to avoid the risk of pollination.
Modern growers who only want to produce high-quality marijuana can avoid the hassle and risks associated with growing male plants completely. They have two primary options: cloning and feminized seeds. While cloning takes specialized horticultural skills, purchasing feminized seeds is easy and just requires finding a reputable seed bank that carries them. Almost all of today’s most popular strains, including both full-season plants and auto-flowers, are available in feminized varieties.
Experienced growers can substantially increase their yields and keep their favorite plants growing for years by keeping a dedicated mother plant and taking cuttings, known as clones. Cloning isn’t an exact science, so growers should note that not all their cuttings will grow into successful weed-bearing cannabis plants.
To clone a female plant, just choose healthy looking branches from the bottom of the plant and use a sterilized knife or pair of scissors to cut the stem at a diagonal. Make sure to keep everything clean and avoid exposing the cut stem to potential contaminants by placing it in clean water until it’s ready to be rooted.
Before transplanting the clone into potting soil, apply rooting solution in a thin layer across the cut end. Make sure not to overdo it, because fresh clones need some air to facilitate root formation. Keep the cloned plants moist and monitor them closely until their root systems begin to form.
As noted above, the process of cloning female plants requires some skill. Novice growers should only expect around one out of every ten clones they produce to take root and thrive. Cloning plants also requires separating the mother plant, especially in indoor grows, to keep it in a vegetative state instead of inducing flowering with the rest of the crop.
Buying feminized seeds requires no additional skill and little preparation. Feminized seeds are just as easy to germinate and grow as ordinary marijuana seeds, so they’re a better bet for those who are just getting started learning about marijuana propagation.
In places where marijuana cultivation is subject to strict regulations, planting female seeds offers a better solution than either taking clones or identifying and pulling out male plants. Around 50% of any handful of ordinary seeds will be male. If growers can only have six plants at a time, having to throw away half of their potential crop every season can be devastating.
Learning how to sex cannabis plants accurately and early is an essential skill for any grower who plans to grow marijuana from seed. Although the chances of a feminized seed turning into a hermaphrodite are extremely slim, mistakes do happen, so even growers who use exclusively feminized seeds should check their plants periodically throughout the pre-flowering and flowering stages. Remember that just one male plant can ruin an entire crop, so put in the extra effort and check each plant as thoroughly as possible.