Pre-flowers on cannabis will begin to show around the fourth (4th) week into vegetative growth, depending on the strain. It is around this time that you will usually be able to determine the sex of your cannabis plants.
Between the fourth (4th) and sixth (6th) node, you will usually be able to find the pre-flowers of the plant. The male cannabis plant will develop tiny, smooth, egg-shaped pollen sacks. While the female cannabis plant will develop small V-shaped white or pink hairs called pistils.
Sometimes it may be hard to tell which are male and which ones are female if you are starting from seed. If you are unsure, you can let them grow for a longer period of time to be sure that you know which ones are which.
If you want to ensure a seedless crop (sinsemilla), you will want to be sure to remove all males from your crop. Male cannabis plants have much lower levels of THC, CBD, CBN, etc than does female cannabis.
Female cannabis plants are cultivated for medical use, due to their higher contents of cannabinoids. If you want to breed crops, you can keep the males to harvest their pollen for future breeding use and you will want to be sure to contain them from the female population so they don’t get pollinated.
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