If you have plants that are already starting to form seeds you've got a choice either keep them and separate the seeds (keep in mind they'll still have SOME THC in them, remember what we used to get in the 70's) or trash them. As I've said before I've never had the issue but I recall, the first indicator is the formation of balls at the branch/stem nodes, if you wait for them to reach a banana "nanners" shape it may be too late to stop pollination. This sexing tutorial with pics might help. How to Tell Sex of Cannabis Plants (with Pictures) | Grow Weed Easy
