They are chiefly dioecious, which means that there are both male trees and female trees, but individual trees can be polygamous (having both hermaphroditic and unisexual flowers) so both male and female flowers can reside on the same tree, but the most common condition is for trees to have only all male or all female
Simply so, do you need two orange trees to produce fruit?
Most citrus trees grown indoors or outdoors are self-fruitful, including oranges, grapefruit, kumquats, lemons and limes. However, some mandarin orange varieties produce more fruit with cross-pollination, but those fruits may have more seeds than those that self-pollinate.
Are there male and female fruit trees?
Without sufficient pollination, they may blossom abundantly but will not bear fruit. Many varieties, though, are “self-unfruitful” and cannot produce fruit from their own pollen; instead, they require pollen from another variety. Some trees, like pecans, have separate male and female flowers on the same tree.
Do trees have a gender?
Most plants are hermaphrodite, but not all – and an interesting situation arises when only one sex is imported into the UK. Most plants are hermaphrodite, even if some of them (hazel, for example) keep their male and female flowers apart. But some plants are dioecious, i.e. they have separate sexes.