How to identify male & female cannabis plants

Updated: May 19, 2018

If you want high-quality seedless cannabis, you don’t want male plants in your garden! In fact, one small male plant can pollinate dozens of females. Pollination makes the female plant produce seeds instead of medicinal compounds like THC and CBD. Seeded cannabis is less potent, less effective and lower quality than unseeded cannabis flowers. Roughly 50% of germinated cannabis seeds are male, so it is important to identify and remove them as soon as possible.


Early Sexual Development


Young seedlings have no discernable sex for the first 12-16 weeks of growth. The earliest clue about seedling sex is vegetative growth form. Juvenile male plants tend to be taller, lankier and faster to mature than their female counterpart. After a few months, tiny premature flowers appear at the growth nodes (bud site) on the main stem. These form where the petiole (leaf stem) and stipule (leaf spur) attach to the main stem. The earliest pre-flowers emerge about three nodes below the top shoot.


Flower Development


At first, the tiny male and female pre-flowers, called calyx, are difficult to tell apart. Both look like small green knobs that are about the size of a grain of rice. You might want a magnifying glass to get a better look.


After a few days it is easier to identify the gender of immature flowers. A tiny stalk emerges extending the male calyx away from the main stem. The male emergence is round and bulbous as it forms green petals that interlock together in a closed fist. Mature flowers hang together like tiny bunches of stubby bananas. Finally, the petals open to release pollen into the wind.





The female calyx attaches tight to the stem. It has a more pinched tip, like a tulip. The eventual emergence of two white “hairs”, called pistils, are a sure sign that the plant is not a male. The pistils that emerge from the tip of the calyx attract pollen from the air. The white hairs are about 5mm long and form a v-shape emerging from the female calyx. When the plant matures, the calyx and pistils cluster together and form a dense cola.


Hermaphrodites


Occasionally cannabis will produce plants with both male and female flowers. This trait, called hermaphroditism, is both genetically and environmentally induced. Many female plants have a latent ability to self-pollinate; however, they will only become “hermie” if there is a major stress, such as an irregular light cycle. Hermaphroditic pollen is just as potent as any other spore, so cull them as ruthlessly as males to prevent a seeded harvest.