Home cultivation represents a sure-fire way to become intimately familiar with cannabis. Many novice growers are surprised to learn that cannabis is a dioecious species, which means that it produces gendered flowers. In times of stress, cannabis can also become hermaphroditic, displaying both female and male sex organs.
Young cannabis plants first begin to demonstrate signs of gender, or pre-flowers, a month after germination while the plant is still in the vegetative stage. These pre-flowers can appear as soon as four weeks after germination. However, it can take up to six weeks before the male pre-flowers are distinguishable from the female pre-flowers. While the signs for gender can be subtle, with practice, a dedicated grower can pick them out. A magnifying glass may be helpful as pre-flowers are often challenging to distinguish with the naked eye.
We'll cover the signs that indicate gender in the pre-flowering stage, but first let's look at why plant gender matters.
Why do growers desire female plants?
Sex matters when it comes to cannabis. Female cannabis plants are prized because they grow cannabinoid-rich buds. Male cannabis plants, in contrast, have less THC content than females. Though some growers do choose to keep male plants for breeding purposes in order to introduce greater genetic diversity into their crops.
Maintaining a crop of exclusively female plants prevents the possibility of male plants fertilizing female plants, leading to seed production. Fertilized female plants don't create as much cannabinoid content as unfertilized females. When a female bud is fertilized, the plant's energy and nutrients are directed to creating seeds, rather than forming THC-rich buds. Seedless female buds are known as sinsemilla and are celebrated for their longer bud-producing life and higher THC levels.
If you're growing cannabis from feminized seeds, or seeds that have been cultivated to produce only female plants, the plants should grow to be exclusively female. With non-feminized or regular seeds, approximately half the plants will turn out to be male.
Do male plants produce buds?
Male plants don't produce buds. The male sex organs of the cannabis plant instead produce pollen sacs that are designed to fertilize the female bud and form seeds. Seedy female buds are undesirable as they provide lower-quality cannabis. It's essential to remove the male and hermaphroditic plants from a crop as soon as possible to protect the quality of the female buds.
How can you tell if a plant is a female before it flowers?
In the pre-flowering phase, the main giveaway of a female plant is the appearance of fine, white hairs known as stigmas protruding from tiny tear-drop shaped buds. Stigmas form part of the pistil, or the female reproductive organs, that are located at the nodes where the branches meet the central stalk.
The wispy, white hairs of the female stigma become visible approximately four to six weeks after germination and progressively darken over time. Pistils and stigmas are more likely to appear closer to the top of the plant near the light source, but they can also form in the lower regions.
How can you tell if a plant is a male?
Like the female plant, the male cannabis plant also has sex organs. Male plants often, but not always, reveal their sex a week or two before female plants. Male plants produce pollen sacs, which also grow at the junction between the node and the stalk. When they first form, the male pollen sacs can initially look similar to the tiny buds that appear on female plants, but they do not have stigmas protruding from them. The male pre-flowers also take on more of a spade-like shape than the tear-drop shape of the young female bud.
There are other morphological differences that distinguish males from females. The male plant frequently grows taller than its female counterpart and has thicker, sturdier stalks to support its weight. Male plants also have fewer leaves than female plants, which tend to be shorter and bushier.
How can you tell if a plant is a hermaphrodite?
Hermaphrodite plants, or “hermies” as they are sometimes known, grow both male and female sex organs. Some cannabis cultivars such as Thai Sativa are true hermaphrodites with the tendency to express hermaphroditism in their genes. However, hermaphrodite plants generally occur as an outcome of stress, such as photoperiod disruptions, nutrient deficiencies, or disease. It's vital to check female plants carefully to ensure the buds are female, and there are no male flowers that could result in the plant fertilizing itself.
Two signs indicate a plant is hermaphroditic. The first and most obvious sign is if the plant grows both male pollen sacs and female buds. The second sign is the appearance of anthers, known colloquially by growers as bananas or “nanners.” Anthers have a curved shape, are typically yellow or lime-green, and appear among buds. Unlike regular male pollen sacs, these anthers can fertilize the female plants as soon as they emerge, so they must be immediately trimmed or removed to protect a female crop.
How can you tell the gender of a seed?
There is no way to determine the gender of a cannabis seed unless you've purchased feminized seeds from a reputable grower. Feminized seeds almost exclusively produce female plants; however, you should still check your crop to ensure no rogue male plants have snuck in. Feminized seeds can also become hermaphrodite plants in times of stress, particularly if they come from dubious genetic lines.
Chemical leaf testing to determine cannabis plant gender
Another method of checking gender is to perform a chemical test of the plant's leaves. This method can be used on a plant as soon as one week after germination. Chemical testing requires a small amount of plant tissue, such as a punch-out from a leaf. While it is a more expensive option than a visual inspection, it is becoming more common among breeders who want to know the gender of their plants definitively.