Understanding the sexual characteristics of cannabis plants is crucial for anyone serious about cultivation. While some species of plants have both male and female parts, cannabis is a dioecious plant, meaning each individual plant is distinctly male or female. Males are obviously necessary for breeding and creating more seeds, but many home grow hobbyists are looking to grow high-producing females for their potent buds.
Most cannabis growers who start their plants from seed are likely using feminized seeds from seed dealers. These are seeds from plants that have been treated with chemicals such as colloidal silver or gibberellic acid to induce male flowers on female plants, resulting in seeds that are almost always female. While this is somewhat unlikely if you are getting your seeds from a reputable dealer, there is still the possibility that a plant turns out male.
As female cannabis plants develop, the buds grow larger and more resinous, hoping to increase their chances of becoming pollinated. When they are pollinated, the production of buds, trichomes, and terpenes will decrease and seeds will form in the flowers. When there are no males present, the plant will continue to go through its life cycle, developing full-sized colas with THC-packed trichomes until they are ready to harvest.
If you are growing cannabis plants from seed, it can be difficult to tell the sex in the vegetative stage without genetic testing. However, there are several ways to recognize a male during the pre-flowering stage. In general, male plants tend to be longer and stretch higher than female plants, which tend to be shorter, wider, and have a greater number of fan leaves. While the differences in mature plants are strikingly obvious, growers will want to remove male as soon as possible to diminish the impact on their female plants.
Male plants may be desirable if you are planning on breeding cannabis plants; however most home growers are hoping to grow unpollinated female plants with large buds. In this case, identifying males early on is crucial, and they must be removed as soon as they are spotted before they spread pollen.
While in the vegetative stage, early flowering sites in female plants will begin to pop up between the branches of the leaves just behind the stipule, a structure on plants which protects young leaves and flowers. Depending on your grow setup, plants may show signs of pre-flowering as early as four to six weeks, during which there may be early signs of sexual characteristics.
Males usually show signs of pre-flowering about one to two weeks before female plants, sometimes as early as three weeks after germination, so this may be an early indication of sex. In female plants, you will notice early pistils emerging from the calyx just behind this structure. This is the easiest way to identify females; eventually this is where colas will form as the plant matures.
In male plants, pollen sacs will begin to form behind the stipule in a more dense, spade-shaped structure. As the plant matures, this structure will change shape and become a ball which looks similar to a preflower. This structure will eventually break open and look like a tiny bunch of bananas that spread pollen.
While clearing out male plants will generally encourage female plants to develop greater bud sizes and more bud sites, the growing environment still needs to be optimally stress-free in order for plants to remain female. Hermaphrodite plants typically occur when no males are present and environmental conditions are stressful, causing the female plants to go into stress mode and start to develop male reproductive structures in order to pollinate themselves. Light leaks, pests, and sudden dips or peaks in temperature can cause a stress response in plants.
Unless you are monitoring all of your bud sites super closely, pollen sacs may appear to pop up suddenly. When examining your plants during the later flowering stage, keep an eye out for the banana-shaped pollen sacs that may pop up on colas. If they are removed soon enough, it can prevent further hermaphroditism, though there is a good chance of pollen sacs continuing to pop up.
Finding just a few pollen sacs doesn’t mean you should expect to see buds full of seeds, but growers will have to remain vigilant and pull off pollen sacs as they appear. Genetics also play a part in this of course, and some varieties are more likely to produce hermaphrodites than others.
While there are plenty of commercial labs in legal states that test for cannabis sex with same-day results, sending off samples may not always be practical or cost-effective. Becoming familiar enough with cannabis development and anatomy to identify plant sex through observation is a skill that all cannabis growers can benefit from.