Signs of Female Plant

Can anyone tell is there a way to tell if a plant is female before it would grow the white hair like pistil things??

some say you can tell if its male or female early by the shape and angle of the stipules

There is a way that i kno of and have used before. What u do is stick a black plastic bag over one branch of ur plant for 24hrs. This tricks the plannt into thinking its dyying, after the 245 hrs, take the bag off and see if there is any pistols or not. If that dont work try using the searcch box on this site to find another technique.

which would begin to prebud first a male or a female or would it be bout the same timing??