The pollination of the Avocado Tree is fascinating. This video shows with a time lapse video exactly how it all works.
The basics are that each flower will open for about 3-6 hours as a female flower on one day. Then the next day it will open for 3-6 hours as a Male flower.
For pollination to occur we need to have both a male flower and a female flower open at the same time.
This is where A- Type Avocados and B- Type Avocados come into play.
The difference between the 2 types is when the female flowers open. A type they open in the morning and B Type they open in the afternoon. ( Visa Versa for Male )
So if you have an A type and a B type you are going to have your Male and Female flowers opening both in the morning and in the afternoon. Giving you cross pollination.
However as this video shows it is possible for both the male and female on the same tree to be open on the same Avocado Tree at the same time. It shows how self pollination can occur.
Watch the video here: https://www.youtube.com/watch?v=Aahzspd1Yzk