As mentioned, there are three races of avocado trees. Of the three, Mexican varieties are the most cold-tolerant, while the West Indies varieties are the least.
Most of today’s popular varieties are hybrids, like the Hass. In addition to the Hass in the U.S., there is another Mexican-Guatemalan hybrid known as Sharwil, which aficionados claim is the tastiest of all avocados. It is grown almost entirely in Hawaii, and is of limited availability elsewhere, because of strict import regulations aimed at keeping pests and diseases from the islands from arriving on the mainland.
Synchronous dichogamy is a fancy term to explain the unusual pollination behavior of avocado trees. Trees can self-pollinate, as noted, but deliver more yields when there are other trees present.
Here’s how the avocado tree does it. The tree’s flowers have both male and female parts, but only one gender is active at a time. Trees known as Type A have flowers that open as female in the morning of one day, open as male in the afternoon of the second day, and then close forever.
Meanwhile, trees known as Type B have flowers that open as female in the afternoon of one day, and as male in the morning of a second day. This means Types A and B together increase the amount of pollen available, and can pollinate each other if planted close enough together for pollinating insects to flit from tree to tree. (All of this only happens when temperatures are just right—above 70 degrees F day and night.)
The different types of avocados ripen at different times of year in the southern climates where they grow. The popular Hass, for instance, ripens April to October, while there are other varieties that ripen between November and June.
That’s just another reason to plant more than one avocado tree: With different types, you can have a year-round harvest of avocados in your garden.
Did you know about the Type A and B flowers of avocados? Please tell us if you’ve grown both together, or tell us how your crop turned out from a single tree.