How does this work in practice? Do other trees from the same species produce male flowers first, and then female? Logically, if all trees produce female flowers in spring and male flowers in the summer then the species can only survive if the seeds can remain viable unfertilized for months (which is probably not that exceptional for plants, I wouldn't know). But if the female seeds are still viable by the time the plant sprouts its male flowers, exactly how does this prevent self-pollination?