Avocado blossoms bloom in two stages. In the first stage, flowers open as a female. In other words they do not produce pollen, but receive pollen. In the second stage, which takes place about three to four hours later (or the next day) the flower opens as a male. The stigma of the male flower releases pollen. Some tree varieties have flowers that start the day as a female, and other varieties have those that start the day as a male. In both cases, the flowers switch over mid-day. On cloudy or overcast days, however, neither type of flower will open in the morning, delaying the start of pollination. When the sun finally does appear, some trees may have both male and female flowers blooming at the same time!
A mature avocado tree may bear a million flowers in a single season. It is no secret that good pollination improves both the yield and quality of avocados. Although avocados are partially self-pollinating, visits by honeybees have been proven beneficial because honeybees transfer large amounts of pollen from flower to flower, tree to tree. It has been estimated that up to 90% of an avocado crop would be lost in the event there were no honeybees. Many commercial avocado growers in California contract to rent thousands of beehives for improved pollination and yield. An estimated 105,000 colonies per year are rented in the United States specifically to improve avocado pollination.