Cross pollination necessary?
Avocado trees come in two types of flowering groups know as type A and type B. You do not necassarily need one of each but it will make the pollination process easier and faster for the plants. There is a lot to it but, simply put. Type A is functionally female while B is functional male then vice versa so they work in harmony to pollinate each other. One plant will pollinate itself but to get more fruit it's better to have at least 1 A and 1 B.