Identifying the sex of a cannabis plant is essential for any grower seeking a usable harvest. Only female plants produce the resinous, cannabinoid-rich flowers, or buds, desired for consumption. Male plants produce pollen that, if allowed to reach a female, will fertilize the flowers. This causes the female plant to focus energy on creating seeds instead of developing potent, seedless buds. Recognizing the visual differences early in the plant’s life cycle ensures the quality and potency of the final crop.
When Plants Begin to Show Sex
Plants reveal their sex during pre-flowering, which occurs a few weeks after the vegetative growth phase. This stage marks the transition to sexual maturity, showing small, immature flower structures along the stem. For most strains, this begins roughly four to six weeks from germination, though timing varies by genetics.
Photoperiod strains initiate pre-flowering only when daylight hours are reduced, typically requiring 12 hours of uninterrupted darkness. Autoflowering strains transition automatically based on age, often showing sex much earlier, sometimes three to four weeks after sprouting. Regardless of the strain type, the structures indicating sex first appear at the nodes, the junctions where leaf stems and side branches meet the main stalk.
Key Visual Markers of Female Plants
The most definitive early indicator of a female plant is the appearance of the female pre-flower structure at the nodes. This structure is a small, teardrop or pear-shaped swelling known as a calyx. These tiny growths are the precursors to the dense, mature flowers.
The distinguishing feature confirming a female is the emergence of one or two wispy, white, hair-like strands from the tip of this calyx. These strands are stigmas, often called pistils by growers. The presence of these white hairs is a certain sign of a female plant, as male plants do not produce them. Growers should use a magnifying glass to examine the nodes closely, as these markers are small when they first appear.
Identifying and Removing Male Plants
Male pre-flowers are structurally distinct and must be identified quickly to prevent female pollination. The male structures appear at the nodes as small, smooth, ball-like sacs, often in clusters. Unlike the female calyx, the male sac is rounded or slightly spade-shaped and never has white, wispy hairs emerging from it.
These are pollen sacs, designed to mature and burst open to release pollen into the air. Released pollen can easily travel and fertilize nearby female plants, ruining the seedless harvest. Identifying and removing male plants, often called “roguing,” should be done immediately upon confirmation of their sex. Carefully remove confirmed male plants from the grow space entirely, taking care not to shake them and prematurely release pollen onto the remaining female plants.
Recognizing Hermaphrodite Plants
A complication in sexing plants is the appearance of hermaphrodite or intersex plants, which display both male and female organs. This occurs due to genetic predisposition or, more commonly, as a survival response to environmental stressors. Stressors like light leaks during the dark cycle, temperature fluctuations, or nutrient imbalances can trigger a female plant to develop male organs in an effort to self-pollinate and produce seeds.
There are two primary visual forms of hermaphroditism. The plant may develop traditional, round male pollen sacs alongside female flowers. Alternatively, it may develop exposed stamens, often called “nanners” because they resemble tiny, pale yellow or lime-green bananas growing among the female flowers. Since nanners are exposed male organs, they can release pollen immediately without needing to open like a sac. Any plant displaying both male and female structures should be isolated or removed entirely to protect the rest of the crop from accidental pollination.