Click here to learn about the importance of A and B pollinator types.
About avocado trees:
Nearly all varieties of avocado trees can be successfully grown in areas with mild winters. If your area is susceptible to freezing temperatures, it is important to select one of the more cold hardy avocado varieties for the best results. All avocado trees need to be protected from heavy frosts and strong winds. They prefer to be planted in sunny locations with well drained soil. Most avocado trees can reach a height of 25'+ feet when fully grown. Selecting the proper location to plant your avocado tree is important for successful growing.
Cultivars of avocados have two different kinds of flowers, "A flowers" and "B flowers". Some cultivars have only "A flowers" and some have only "B flowers". Production is best with cross-pollination between two cultivars, one with A flowers and one with B flowers. "A flowers" are receptive to pollen in the morning and shed pollen the following afternoon while "B flowers" are receptive to pollen in the afternoon, and shed pollen the following morning. Consequently from a technical standpoint, production is best with cross-pollination between two cultivars, one with A flowers and one with B flowers.
But the reality is, most cultivars of avocado seem to get better and better at producing fruits as they get older, another pollinator or not. And if you live in a good avocado growing climate, there's almost invariably another avocado tree in the neighborhood that will be your avocado tree's buddy in the next many years.