Growers identify plant sex by identifying pre-flowers, which are small structures that form at the nodes during late vegetation.
Within a matter of weeks, these small pre-flowers swell into dense nuggets and begin churning out cannabinoid and terpene-rich resin. Since you the removed males and prevented pollination, your flowers will continuously produce resin until the end of the growing cycle.
The ability to determine plant sex as early as possible is a critical skill for cannabis growers. As you develop this eye for identifying plant sex, you will be able to prevent any accidental pollination.
IDENTIFYING FEMALE CANNABIS PLANTS
Male pre-flowers look like tiny green eggs or “balls”. These young pollen sacs will look smooth and won’t possess any fine hairs, or any distinct point. Later into the flowering stage, pollen sacs begin to form larger and denser clusters. They’ll become easy to identify with the naked eye by this point. However, pollen sacs usually begin to disperse their contents around 2–3 weeks after forming. Be sure to remove them from your space with haste if you don’t plan on crossing your plants.
Cannabis growers and breeders use this trait to their advantage, since it allows them to separate male and female plants. This enables them to prevent the flowers from becoming fertilised and going to seed, which results in better quality flowers, known as sinsemilla.
Female cannabis plants are the main focus of casual growers looking to harvest a personal stash. But, depending on their genetics, female plants can look drastically different from one another. Some remain small, producing dense canopies and significant lateral growth. Others grow in excess of 3m, produce massive harvests, and look more like trees than regular garden plants.
These protruding structures are designed to capture pollen, which leads to fertilisation. They stick out away from the flower to capture pollen from the air, and to await being brushed up against by pollen-covered insects.
Getting clones of female marijuana plants or buying feminized seeds online from a seed bank are other ways you can ensure that all your marijuana plants are female.
Only a female marijuana plant makes flowers/buds that contain a usable amount of THC. Male marijuana plants only make pollen to fertilize the females with. Most growers will throw away any male plants that they encounter to keep them from fertilizing the female plants. If your female plants do get fertilized, they will use all their energy to produce seeds instead of making buds. This is good if you want seeds, but you will run into the same problem since half of the seeds will also be male.
If you would like to start a breeding program to make your own hybrids, I recommend using a method that creates all-female (feminized) seeds so that you don't waste time having to identify and throw out male plants.
If you don't have a choice of seeds, and some of your seeds may be male (like if you just found seeds) than you will want to get your plants to reveal their gender right away so you don't have to waste time and energy on male plants.