The type A vs type B avocado sort is set by genetics, not by leaf shape or bark or fruit color. You can not eyeball it from across the yard. The only sure way to tell is the variety name or a careful watch of when the flowers open. Both types share the same odd two day bloom dance.
I tracked this myself with a Hass and a Bacon in my own yard for one full week. The Hass flowers opened up female right after sunrise. They closed up by noon. The next day those same flowers swung open as male in the late afternoon. The Bacon ran the clock in reverse. Avocado pollination clicked into place after I saw it once.
UC Riverside lays out the science behind this odd habit. Type A trees open as female in the morning and as male the next afternoon. Type B trees open as female in the afternoon and as male the next morning. The pollen of one type lines up with the open female flowers of the other type. The two types fill in for each other across the day.
This split is called avocado flower type and it covers every avocado on earth. The cool part is the same tree never has both flower sexes open at the same time. That dance keeps the tree from self pollinating most of the year. A second tree of the matched type really helps the fruit set in cool spring weather.
Here is a quick Hass avocado type list you can save right now. Type A trees: Hass, Reed, Pinkerton, Lila, Mexicola Grande, Lamb Hass, Gwen. Type B trees: Bacon, Fuerte, Zutano, Sir Prize, Sharwil. The Bacon avocado type is a top pick because it tolerates cold down to 25°F (-4°C). Most home growers I know plant a Hass with a Bacon or a Fuerte. Both pairings work well in southern California and similar climates.
What if you bought a tree with a lost tag from a swap meet? You have two real options on the table. Watch the flowers for a week in spring. Open in the morning means type A. Open in the afternoon means type B. The second option is to drop a leaf or fruit photo at your local extension office. A trained eye can often name the variety from fruit shape and skin.
I learned the hard way that nursery tags get swapped. A friend planted what the tag called a Reed. The tree turned out to be a Zutano. The fruit shape gave it away two years in. Now I write the variety name on a metal tag and wire it to the trunk on planting day. You save yourself years of guessing with this one small habit.
Does cross-pollination avocado work really matter for a backyard with one tree? Some growers swear they get full crops with one Hass and no partner near by. Honest answer is yes and no. A single tree can set fruit thanks to bees and warm weather and overlap with neighbors' trees a block away. Yields jump 30 to 50% when a matched A and B pair grow side by side.
Build your list before you head out to shop. Pick one tree for your yard from each column. Plant them within 30 feet (9 m) of each other so bees can hop between your flowers. A Hass with a Bacon covers most home yards. A Pinkerton with a Fuerte adds a longer harvest window for your kitchen. The only reliable test is the variety name on your tag, so make sure your nursery confirms it for you in writing before you pay.
Read the full article: Avocado Tree Care: Water, Soil, Feed
