Synchronous Dichogamy: How Avocado Trees Flower and Set Fruit
If you've ever looked closely at an avocado tree in bloom, you've seen thousands of tiny yellow-green flowers clustered along the branch tips. A mature Hass tree can produce over a million flowers in a single season. But here's the surprising part: fewer than one in a thousand of those flowers will ever become an avocado. The reason comes down to one of the most unusual reproductive strategies in the plant kingdom — synchronous dichogamy.
What Is Synchronous Dichogamy?
Dichogamy means a flower's male and female parts mature at different times. In avocados, this is taken to an extreme. Each flower actually opens twice — once as female and once as male — on a precise schedule. During the female phase, the flower's stigma is receptive to pollen, but the stamens stay closed. The flower then closes for the night. When it reopens the next day, the roles reverse: the stamens shed pollen, but the stigma is no longer receptive.
The "synchronous" part means that all the flowers on a given tree follow the same schedule at the same time. So when every flower on a tree is in its female phase, there's no pollen available from that tree — and when they're all shedding pollen, there's no receptive stigma to receive it. The tree essentially prevents self-pollination by design.
Type A and Type B: A Botanical Dance
Avocado cultivars are divided into two flowering types — Type A and Type B — based on the timing of their opening cycle.
Type A flowers (like Hass, Lamb Hass, and Reed) open as female on the morning of day one, close that afternoon, then reopen as male the afternoon of day two.
Type B flowers (like Fuerte, Bacon, and Zutano) follow the opposite schedule. They open as female on the afternoon of day one, close overnight, then reopen as male the morning of day two.
When you plant Type A and Type B trees near each other, their schedules overlap beautifully. One tree's male phase coincides with the other's female phase, allowing cross-pollination. This is why many avocado growers — including us here at Patel Ranch — interplant different cultivars throughout the grove.
Our own grove is a great example. The trees were originally planted in 1974, and whoever designed the layout understood dichogamy well. Across roughly 15 acres, we have about 11.4 acres of Hass (Type A) and 3.6 acres of pollinizers — mostly Fuerte (Type B) at 3.25 acres, with a small planting of Zutano (also Type B) at just over a third of an acre. That roughly 22% pollinizer ratio ensures there's always Type B pollen available when our Hass flowers are in their female phase.
The Role of Bees and Other Pollinators
Avocado flowers don't rely on wind — they need insect pollinators to move pollen from one flower to another. Honeybees are the primary pollinators in most California avocado groves. During bloom season, you'll see our trees buzzing with activity as bees work through the flowers collecting nectar and inadvertently transferring pollen between trees.
The timing is critical. Bees are most active during the warmest part of the day, which conveniently overlaps with when avocado flowers tend to be open. Cool or overcast mornings can delay flower opening and reduce bee activity, which is one reason that temperature during bloom has such a big impact on the season's crop.
From Flower to Fruit: The Long Road
Once a flower is successfully pollinated, the real work begins. The tiny fruitlet starts to develop, but most will drop off the tree in the first few weeks — a natural process called fruitlet abscission. The tree simply can't support a million fruits, so it sheds the majority and channels its energy into the survivors.
The avocados that hang on enter a long growing period. Unlike most fruits, Hass avocados don't ripen on the tree. They can stay on the branch for months, slowly building oil content and growing larger. This is actually an advantage for farmers — the tree acts as natural cold storage, and we can pick fruit over an extended harvest window rather than rushing to get everything off at once.
In De Luz, our harvest season typically runs from spring through fall. The long hang time in our favorable microclimate allows the fruit to develop the high oil content and creamy texture that California Hass avocados are known for.
Why This Matters for Our Grove
Understanding dichogamy isn't just academic — it directly shapes how an avocado grove is designed. When our grove was originally planted in 1974, the grower who laid it out clearly understood this science. They deliberately interplanted Fuerte and Zutano (Type B) among the Hass (Type A) so that cross-pollination would happen naturally every bloom season. More than fifty years later, that thoughtful design still pays off — and it's something we're careful to preserve as we care for these trees. We time our irrigation and nutrition programs to support the trees through the energy-intensive bloom period, and we pay close attention to weather forecasts during flowering, because a few cold days at the wrong time can significantly affect the year's yield.
It's one of the things we find most fascinating about growing avocados. Every piece of fruit that makes it to your table started as one flower among a million — pollinated at just the right moment, on just the right day, by a bee that happened to visit a neighboring tree first. There's a lot of nature's precision behind every avocado.
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