I have always thought that you should just remove all male plants so that the female are not pollenated, though I think I may be wrong. My friend reminded me of something we heard back in high school biology about the plarts of flowers. He asked me why we couldnt just remove the stamens (the part that produces the pollen). Im not really sure what weed plants are considered to be, whether theyre flowers, weeds or something else. Up until now Ive never really questioned it. Im not familiar with the anatomy of a weed plant but I think the stamens are either the little things (cant think of the word) that you look for instead of the pistils when sexing. This might be completly bogus but if it sound plausible then please say something.