Normally it shows the sex about 2-3 weeks before it actually starts flowering. Clusters of flowers known as buds or colas only occur on female or hermaphrodite plants. Hermaphrodites are plants that are part male, part female. If you want sinsemilla buds, make sure you only have pure females.
Early female marijuana flowers look like little furry hairs, usually white, but they can be other colors. Early male flowers look a bit like small bunches of mini green bananas. Hermie plants will have both! Look near the leaf joins on your plants to see them emerging. ALWAYS seperate the males from the females as soon as possible or your baby girls will be pollinated and will cause all them juicy buds to be filled with seeds instead. Plants in constant light can sometimes start to show some pre-flowers after only a few weeks of growth. Usually though it takes a change in light cycle to trigger the plants into full reproductive mode.
Most varieties of marijuana require 12 hours of darkness per day to induce their flowering cycles. Sativa varieties sometimes need more. Indica varieties can sometimes take less. Hope this helps! Good luck buddy!
