@Aoitenshi
It depends on the tree species, some are self fertile but others are not. For sure example cities only allow you to plant male ginkgo trees because the female ones bear fruit, it’s more of a nut, but it’s a danger to damaging cars and the outer shell is smelly and stains things. The nut itself is supposed to be yummy and nutritious though. I’ve never had one before. Lots of common fruit trees like apples also need two trees or more to make fruit.