Cannabis plants are naturally dioecious, meaning they develop as either male or female individuals. Distinguishing between the two is necessary for a successful harvest. Female plants develop the cannabinoid-rich flowers, or buds, sought after for consumption. Male plants produce pollen sacs, and if left in the same space, they will fertilize the females. This fertilization causes females to divert energy away from flower production to create seeds instead. Early and accurate sex identification protects potency and maximizes crop yield.
When Plants Begin to Show Sex
A cannabis plant typically reveals its sex during pre-flowering, which occurs when the plant reaches maturity, usually three to eight weeks after germination. The signs are visible at the nodes, the points where leaves and branches extend from the main stem. For photoperiod strains grown indoors, growers trigger flowering by changing the light schedule to twelve hours of light and twelve hours of darkness. This signals the plant to form reproductive structures.
The pre-flowering structures become visible within one to two weeks after the light cycle change. Male plants often exhibit these pre-flowers about a week or two earlier than females. This earlier display provides a window to identify and remove males before they release pollen. Growers must closely inspect the nodes during this transitional phase.
Visual Identification of Male Pre-Flowers
Identifying a male plant requires inspecting the nodes for pollen sacs. These structures appear as small, smooth, ball-like formations that lack protruding hairs. They are the plant’s anthers, containing the pollen necessary for reproduction. Initially, a male pre-flower may appear as a single, tiny sphere on a short stalk where the branch meets the main stem.
As the male plant matures, these individual sacs cluster together, eventually resembling tiny bunches of grapes or small bananas before they open. These clusters are a definitive sign of a male plant. If not removed promptly, the sacs will burst open, releasing pollen that travels through the air to pollinate nearby females. Immediate removal of any plant displaying these structures is necessary to safeguard the grow space.
Visual Identification of Female Pre-Flowers
The presence of a female plant is confirmed by a different type of pre-flower structure at the nodes. The female pre-flower is a calyx, a small, tear-drop, or pear-shaped structure. This protective casing is where the female reproductive organs develop. The most distinct identifier of a female plant is the emergence of fine, hair-like strands from this calyx.
These strands are known as pistils or stigmas and are typically white or clear in color. They emerge in pairs from the pointed tip of the calyx and are designed to catch airborne pollen. When these white pistils are visible, the plant is confirmed female and will proceed to develop the large, resinous flowers. These structures will multiply and swell during the full flowering phase, eventually forming dense buds. Observation with a magnifying glass can help distinguish the subtle shape differences between the male’s round sac and the female’s pear-shaped calyx, even before the white hairs appear.
Recognizing Hermaphroditic Plants
While cannabis is typically either male or female, some plants may exhibit both reproductive organs on the same individual, a condition known as hermaphroditism. These plants can self-pollinate, making them detrimental to a seedless crop. One form involves fully developed male pollen sacs on one part of the plant and female flowers on another. Growers must inspect the entire plant, as both smooth balls and pistil-bearing calyxes can be found at different nodes.
A second form of hermaphroditism is the development of “nanners,” which are exposed male stamens. These look like small, yellow or lime-green banana-shaped protrusions growing directly among the female flowers. These stamens do not need to open like traditional pollen sacs; they are already exposed and can shed pollen immediately. Hermaphroditism is often triggered by genetic predisposition or environmental stressors, such as light leaks during the dark period or extreme temperature fluctuations. Identifying and removing these mixed-sex plants or carefully pruning the affected branches is necessary to prevent accidental pollination.