How old does the weed plant have to be to tell the sex of it?

Cannabis plants typically show their sex around 4 to 6 weeks into the vegetative stage, when they are about 6 to 12 inches tall. At this point, pre-flowers develop at the nodes, revealing whether the plant is male, female, or hermaphrodite. Early identification is crucial for growers to manage their crops effectively, especially when breeding or preventing pollination.