Type A and Type B Avocados: How Hass, Fuerte and Bacon Share the Pollen

Avocados can self-pollinate and they can cross-pollinate. The catch is timing. A Hass flower opens as female in the morning, closes, and opens again as male in the afternoon of the following day, so its pollen and its receptive stage do not always overlap. That is why growers plant Type A and Type B trees together.

In our grove, the Hass trees are Type A. Our Fuerte and Bacon trees are Type B, and they run on the opposite clock. When the timing does not line up either way, the bees carry the day.

What does it mean for a flower to be female, then male?

Every avocado flower has both female and male parts. What makes the avocado unusual is that those parts are not active at the same time. Each flower opens twice. On its first opening it is functionally female: it can receive pollen but does not release any, and that stage lasts only two or three hours. It closes, and on its second opening it is functionally male, shedding pollen but no longer receptive.

Botanists call this synchronous dichogamy. It is the tree’s way of encouraging pollen to move between different trees rather than stay on the same flower.

Type A versus Type B

Avocado varieties fall into two groups based on when their flowers open in each stage:

• Type A (such as Hass, Reed, Gwen and Lamb Hass): female on the morning of day one, male on the afternoon of day two.
• Type B (such as Fuerte, Bacon and Zutano): female on the afternoon of day one, male on the morning of day two.

Put them side by side and the schedules fit together. In the morning, Type B flowers are shedding pollen just as Type A flowers are open and receptive. In the afternoon, it flips. There is pollen available at nearly every point in the day when a flower is ready for it. That neat clockwork holds in warm weather, when the average of the day’s high and the night’s low is above about 70°F.

Planting both is common practice in California groves, and Fuerte and Bacon are two of the classic partners for Hass. Distance matters: bees mostly work within one to three trees, and in one study Hass trees right next to a Type B averaged 205 fruit a tree, against 54 for trees fifteen rows away. We have written more about how those varieties differ at harvest time in why bloom dates do not predict harvest.

So can a Hass pollinate itself?

More often than people expect. The flowering schedule is not perfectly rigid. In cool spring weather the openings are delayed and irregular, so a single tree carries female-stage and male-stage flowers at the same time — which is how large solid blocks of one variety still set heavy crops. University of California research found that self-fertilization accounts for a substantial share of fruit set in California groves, and a lone Hass in a backyard can set fruit. What does not work well is a single flower pollinating itself; caged trees kept away from bees set very poorly. So it is not guaranteed, which is why the video says self-pollination is not always possible.

The bees do the heavy lifting

Flower timing only matters if something moves the pollen, and avocado pollen does not travel far on the wind. That job falls to insects, bees above all. When the Type A and Type B timing does not line up, the bees are still out there working every tree and making up the difference.

Anything that brings more pollinators into the grove during bloom helps. One simple trick we like is covered in how planting sunflowers boosts avocado pollination. And when pollination goes a little sideways, you can end up with oddities like the seedless avocado cuke.

Every avocado we ship started as one of those flowers, pollinated with help from a bee. Taste the Type A side in our 4lb Hass box and the Type B side in our 4lb Fuerte box — each ships when its trees are bearing, with a waitlist on the page in between. Until the trees are picking again, the avocado scoop, the Hawaiian shirt and our hats ship year-round.

This post is part of our guide to growing avocado trees.