Unless they autoflower. You can't tell till you go to 12/12 light and see the first signs of preflower. If you are growing mothers too clone from then you take a clone. Root it and put it into 12/12 to see what it is. Mark them good so you know witch mother or father it came from. Then you know you have all females in flower and don't lose space or time. It's the way to go if you don't have a big room.