Distinguishing male from female cannabis plants is a fundamental skill for cultivators. This process, known as sexing, is performed early to ensure a successful harvest. Only female plants produce the cannabinoid-rich flowers, or buds, sought after for their potency and yield. Male plants produce pollen sacs, and if left with females, they will cause the flowers to produce seeds. Removing males immediately maximizes flower production and prevents the crop from becoming seeded.
When to Begin Sexing Your Plants
The earliest signs of a plant’s sex appear during the pre-flowering stage, as the plant transitions from the vegetative growth phase. This transition is naturally triggered by a change in the light cycle, specifically when the plant receives about 12 hours of uninterrupted darkness each day. For plants grown from seed, pre-flowers usually become visible between the fourth and sixth week of growth. Male plants often reveal their sex sooner, sometimes as early as three to four weeks from germination.
The most reliable visual identification occurs when the plant has fully entered the transition phase after the light schedule has been adjusted. Pre-flowers emerge at the nodes, which are the junctions where the leaf stems meet the main stalk. Growers must carefully inspect the nodes during this window to identify and remove any unwanted males before their pollen sacs mature and open.
Identifying Male Pre-Flowers
Male pre-flowers are distinct in shape, appearing as small, smooth, ball-like structures at the nodes of the plant. These growths are immature pollen sacs that will eventually mature and release pollen. They are often compared to tiny spheres or miniature bunches of grapes clustered at the intersection of the stem and branch. They lack any protruding hairs or features that would suggest a female plant.
Upon close inspection, a male pre-flower may appear on a short stalk, hanging slightly away from the main stem. As the plant matures, these sacs multiply and swell, indicating the plant is rapidly approaching the point of pollen release. Early identification is imperative, as even a single open pollen sac can compromise the quality of an entire female crop. Growers should remove any plant displaying these smooth, round sacs immediately to prevent accidental pollination.
Identifying Female Pre-Flowers
Female pre-flowers are characterized by a tear-drop or pointed shape, known as a calyx, which emerges at the plant’s nodes. The definitive indicator of female sex is the presence of one or two fine, white hairs, called pistils, that emerge from the tip of this calyx. These delicate pistils are the plant’s stigmas, designed to capture airborne pollen. The female pre-flower is generally longer and narrower than the male’s round sac.
The appearance of these hair-like structures confirms the plant’s sex, even when the calyx is very small. The female calyx is the protective casing for the ovule and is the precursor to the larger, resin-producing flower. Distinguishing the female’s pointed calyx with its wispy white hairs from the male’s smooth, round ball is the primary focus of early sexing.
Recognizing Hermaphroditic Plants
A hermaphroditic plant, often called a “hermie,” develops both male pollen sacs and female pistils on the same plant or on different parts of the same plant. This biological occurrence can happen due to genetic predisposition or as a stress response to adverse environmental conditions, such as light leaks during the dark cycle or extreme temperature fluctuations. The presence of both sexes poses a significant threat because the plant can self-pollinate, leading to seeded flowers and a reduction in overall potency.
Two types of hermaphroditism are commonly observed: a true hermaphrodite with distinct male and female reproductive structures, and a plant that develops “bananas.” These “bananas” are stamens, the male parts that hold the pollen, emerging directly from the female flower tissue without the protective sac. Any plant displaying both sexes should be removed from the grow space immediately, as its viable pollen can quickly ruin a harvest.