Given that a tree is healthy and making lots of flowers, there are three main external conditions that create ideal avocado pollination potential: warm weather, lots of bees, and different varieties blooming near each other.
While I’ve seen these elements work together for good avocado fruitset in my yard and elsewhere, below I note snippets of more robust evidence from others. Click the reference links for the full stories.
High mean temperature (average of daily high and nightly low): “Ordinarily, the higher the temperature mean, the more favorable the set prognosis. This explains why most of our set is usually toward the end of the blooming period.” Bob Bergh in 1967
How high? “Daily means above 60° are necessary before much fruit will set; and means above 65° give the best fruit set.” Len Francis in 1974
B types need it warmer than A types: Shepherd (B) needs five degrees F higher than Hass (A) for “potentially favourable fruit-set.” Birdie Carr of Australia in 2019
What to do? “We have no control over the weather!” you say. True, but by growing the most suitable varieties for our location we can achieve results as if we had some control. For example, since B type avocado varieties require warmer weather than A types, if you live right on the beach where spring days don’t warm up or at the bottom of an inland valley where spring nights dip down low you can grow an A instead of a B to increase your pollination chances. Now that’s a crop!
Need for bees: “The evidence from our caging experiments indicates the following. Practically every avocado fruit set means that a honey bee transferred pollen to that flower, from some other flower.” Bob Bergh in 1967
More bees the better: ” . . . an average count of 40 bees per medium size tree is a good number.” This is research from Gad Ish-Am as presented by Reuben Hofshi.
Not only honeybees: Other effective pollinators observed include bumblebees, numerous species of stingless bees, and even wasps and flies. Pollinators of Avocado by Ish-Am et al.
What to do? To bring in more bees you can install a bee hive or simply provide food for them, as I explain how I’ve done in my post, “Growing a Bee Garden” A honeybee on an avocado flower in my yard.
Different varieties: “The data from the various groves observed show that trees of a given variety frequently set more fruit when located proximate to a second variety than when located farther removed from the other variety.” Bob Bergh in 1964
Varieties of different flower types even better: “Interplanting an A and a B variety, provided that their blooming season overlaps adequately, thus provides maximum opportunity for cross-pollination. We have thereby obtained yield increases up to 150% in individual years, with 50% increases frequent.” Bob Bergh in 1967
Closer together the better: “Close watching showed that bees have a strong preference for sticking to one avocado tree at a time . . . But as can be observed bees do cross freely when the foliage of two varieties interlace, with no open space between.” Orange Clark in 1922
Here’s a two-minute video version of the ideas in this post, showing trees in my yard:
Having warm weather during bloom, seeing lots of bees visiting female flowers, and different varieties of avocado trees growing near each other don’t guarantee fruit. And cooler weather, few bees, and a lone avocado tree can still end up with a decent crop. But the presence of these three ingredients is almost always correlated with higher pollination and fruitset in avocado trees.
“The Avocado Flower and the Pollination-Fruitset Process: Ideas from a California Perspective” by Mary Lu Arpaia and Reuben Hofshi
Avocados are one of my favorite fruits to grow in my garden. Their rich, creamy texture and healthy fats make them a nutritional powerhouse. However getting good yields from avocado trees can be tricky due to their unusual flowering habits. In this comprehensive guide I’ll walk you through everything you need to know to successfully hand pollinate your avocado plant and maximize fruit production.
Avocado trees have both male and female flowers. The male flowers have pollen-producing anthers while the female flowers have a stigma to receive pollen.
Here’s the tricky part – avocado varieties are classified as either Type A or Type B. Type A varieties open as female in the morning and male in the afternoon. Type B varieties open as male in the morning and female in the afternoon.
This means in order to get good pollination, Type A and B trees need to be planted together or pollen needs to be manually transferred between flowers. Even self-pollinating varieties will benefit from cross-pollination with another type of avocado.
Common Type A varieties: Hass, Reed, Pinkerton
Common Type B varieties: Fuerte, Bacon, Zutano
When to Hand Pollinate
The best time for hand pollination is mid-morning when the temperatures are cooler. You’ll need to observe your tree to find the 1-2 hour overlap period when both male and female flowers are open. This typically occurs around mid-day.
Ideally, choose a calm, sunny day without rain or wind for pollinating. Wind and rain can damage delicate flowers.
Collecting Pollen
To collect pollen, you’ll need to identify newly opened male flowers that have started releasing pollen. Look for flowers where the tips of the anthers appear dry, cracked or fuzzy – this means they are dehiscent and releasing pollen.
Gently pluck a male flower and remove its petals to access the anthers inside. Use a small paintbrush, cotton swab or stick wrapped in cobwebs to collect the pollen. Store collected pollen in a sealed container in the refrigerator if you won’t be using it right away. Pollen remains viable for up to a day when properly stored.
Transferring Pollen
Once you’ve collected fresh pollen, it’s time to pollinate the female flowers. Identify newly opened female flowers by their large, bulbous base and single stigma protruding from the center.
Use your pollen-coated tool to gently dust pollen onto the stigma. Repeat this process across multiple female flowers on different parts of the tree. I like to hit flowers on all sides of the canopy to improve chances of pollination success.
Alternative Pollination Methods
If you don’t want to pluck male flowers from your tree, you can try gently brushing pollen directly from male flowers onto female flowers during the overlap period when both are open. This takes a bit more finesse but preserves all the tree’s flowers.
Another option is to plant two compatible avocado varieties within 20 feet of each other. This allows cross-pollination via wind or pollinating insects like bees. But even closely planted trees will benefit from supplemental hand pollination.
Improving Pollination Success
Here are a few tips to increase the likelihood your hand pollination efforts will result in viable fruit:
- Pollinate female flowers across the entire canopy – top, bottom, sides, inside.
- Use fresh pollen collected the same day whenever possible.
- Pollinate every few days throughout the bloom period to hit all new flowers.
- Provide optimal care like consistent watering and good drainage.
- Consider adding a bee garden to attract more pollinators.
Welcome . . .
Im Greg. My goal is to help you grow food at home, with a focus on vegetables and fruits — especially avocados — in Southern California. I write a new “Yard Post” every Friday.
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How To FERTILIZE AVOCADO TREES For INSANE Fruit Set [COMPLETE GUIDE]
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