In July it becomes evident whether your avocado tree will have a crop to eat next year. Do you see small avocados on the tree now? Do you see many?
If your answer to either question is no, then this post should give you a clue as to why not. If you have an avocado tree that has never made fruit, or that has never made much fruit, or that has no fruit this year, I’ll help you understand why. And of course, I’ll share ideas on how to improve the situation.
Did the tree flower?
First, during the spring, did your avocado tree make flowers? If it did not, then there was no hope for fruit this year. In general, avocado trees flower once per year, and this mostly happens in the spring. So if your tree didn’t make flowers this past spring, then you must wait with hope for next spring. If your tree did flower, then it had a chance to make avocados, as the fruit comes from the flowers.
Let’s start by looking into trees that make flowers but don’t end up with avocados, or at least don’t end up with many avocados. Later we’ll look into trees that don’t make flowers.
YES, THE TREE FLOWERED
There are seven main reasons that an avocado tree will make flowers and yet not make avocados.
The first one is that the tree is a Fuerte. Alas, the Fuerte variety is well known to include individual trees that are barren. I have experienced this firsthand: I have an eight year-old Fuerte that flowers abundantly every year and yet has never produced a single full-sized avocado. I have also seen numerous other Fuertes in varied locations throughout Southern California that are drones as well. (More on this in my profile of Fuerte.)
What’s wrong with these Fuertes? In short, they have defective flowers. (Details in my post on avocado cukes.)
Fuerte is a B-type avocado, and that means its flowers become female in the second half of the day. There are lots of other B-type avocado varieties, such as Zutano, Sharwil, Bacon, Ettinger, and Edranol. On the whole, B-type avocado varieties are not as productive as A types, especially in locations that have chilly nights or low average temperatures overall. (See this paper by Peter Peterson.)
I’m in such a location (chilly nights), and my B-type avocado trees don’t produce as well as my A types. Nevertheless, some B types are consistently more productive than others. I’ve found that Edranol produces well in my yard, for instance.
As another example, Ellen Baker and Freddy Menge of Epicenter Avocado Nursery near Santa Cruz are in a cool coastal location and they have also found that A types produce better than B types, in general. Yet Zutano is a good producer on their property. (Read more about their results with Zutano and other B types here.)
Some other B types might produce well in years when the spring weather is warmer than normal, but have no crop in cool springs. Sharwil is a variety that has frustrated many with such a fickle fruiting habit, which is at least partly related to temperatures during bloom. Sharwil is particularly frustrating in this respect because its avocados are among the finest in eating quality.
If you have a B-type avocado tree that isn’t producing fruit in your yard after more than about five years, I would cut your losses and remove the tree and replant with an A type or graft it over to an A type.
Help of a pollenizer
Every avocado variety that I know will produce fruit as a lone tree. In other words, you do not need two avocado trees to get fruit. That said, every avocado variety that I know will produce more fruit if there is another avocado variety in bloom at the same time near it.
So this is something to consider if your avocado tree is flowering and making a little fruit but not as much as you think it could. Although adding a pollenizer tree can increase fruit production, do note that it won’t make a barren tree fruitful (as far as I’ve ever seen or read).
Not enough flowers
Your avocado tree flowered in the spring, but did it flower a lot? Avocado trees are unskilled at turning their flowers into fruit compared to most other fruit trees. Peaches can turn almost every flower they make into a peach, but in contrast, avocado trees end up shedding most of the flowers they make.
Back in 1960, the University of California’s avocado breeding program was located in Los Angeles, and there they found that through hand pollination they usually had about a one percent success rate. That is, for every hundred flowers pollinated, they usually got a single avocado. Sometimes they only got one avocado out of one thousand flowers. (See this report by Shroeder in the 1960 California Avocado Society Yearbook.)
Therefore, if your tree made only a few hundred flowers this spring, which might seem like a lot, you still ought not expect a bunch of avocados.
One reason an avocado tree flowers only mildly — and then sets few fruit — is if it isn’t getting enough sun. More sun equals more flowers equals more avocados.
Heat or water stress during or soon after flowering
It is said that avocado pollen loses viability at temperatures of around 95 degrees. And it is said that newly set avocado fruit (the size of BBs or peas) are vulnerable to dropping at about the same temperature. (See here and here.)
So if there’s a heatwave during flowering, an avocado tree can fail to set fruit. And if there’s a heatwave soon after flowering, an avocado tree that set fruit can lose it.
I lost entire, newly set, crops on two trees during a heatwave in early July 2018, when the temperatures got up above 110 degrees.
Some avocado farmers in Israel and Australia and California have erected sprinklers over the tops of their trees in order to cool the trees during high heat during these seasons of vulnerability, and they’ve seen improved crops as a result. (See the California Avocado Society’s June 2022 seminar video on “Heat Mitigation around the World.”)
In addition to heat, mere thirst can stress an avocado tree enough such that it drops some tiny fruitlets too. So if a tree is not being watered enough while its fruit are young (think May, June, and July mostly), then it will drop more of that fruit than it otherwise would.
I had a good number of avocados set on a young Hass tree this spring, and then the irrigation was accidentally turned off on the tree for a few weeks. My fault. The leaves started to brown and every little avocado dropped.
There’s always some fruit drop, but we can do things to help keep it to a minimum, such as making sure the irrigation system is working!
Few bees and flies
The only way avocado flowers become fruit in California is through a visit from an insect, usually a bee and sometimes a fly. If there are few bees and flies around when your avocado tree is in bloom, you can expect few, if any, fruit.
(See the earliest experiments with netting avocado trees to keep in or keep out bees and flies done in Point Loma, San Diego back in the 1920s.)
How many bees might be enough for good fruitset? Gad Ish-Am, a researcher in Israel, concluded that seeing about 40 bees at a given time on a medium-sized tree (which I would guess means about 15 feet tall) while the tree is in full bloom on a warm day is enough. (See details here.)
Why might there be few bees and flies around your tree? Pesticides sprayed in the area can kill them. And they won’t live near your tree if there isn’t food there throughout most of the year; for bees, food means flowers so there must be flowers around for them to feed on.
(See my posts, “Growing a bee garden” and “What are the best avocado pollination conditions?” for ideas on increasing populations of bees and flies.)
Avocado trees bought at a nursery are usually grafted and therefore made of two parts: a rootstock and a scion. I’m not aware of any rootstock that has been found to totally prevent fruit production in the scion (the top part that makes the fruit), but it has been well documented that rootstocks influence the amount of fruit production.
A famous case concerns the rootstock variety Martin Grande, which researchers at U.C. Riverside were very excited about for a time because it was highly resistant to the disease called root rot, only to be abandoned after Hass scions grafted onto Martin Grande (and its seedlings called G755) ended up making only about half as much fruit as those grafted onto other rootstocks. Who cares if the trees don’t decline from root rot if they make few avocados in the meantime, right?
Blaming the rootstock for a tree that barely makes fruit would be my last excuse, but it is a factor.
(More on Martin Grande at 1:10 in this video of June 2020 California Avocado Society seminar and in this paper from J.S. Kohne in South Africa.)
(More on avocado rootstocks in general in my post, “Avocado rootstocks: what do they matter?”)
NO, THE TREE DID NOT FLOWER
Now to look into a tree that does not make avocados because it does not make flowers. I see six main reasons.
One is that the tree was grown from a seed and has not been grafted. Most avocado trees grown from seed and never grafted take at least five years before flowering. A few rare seedlings flower after only a couple years (seedlings of Pinkerton have been said to do this) while others don’t flower after more than a decade.
In the case of a seedling, you must be patient and wait for your seedling avocado tree to grow through juvenility and be mature enough to reproduce (for that is what making avocado fruit is). Such seedling trees can reach twenty feet tall before they make any flowers.
Young but not precocious
Another reason an avocado tree doesn’t bloom is that it simply is not a precocious variety. Some avocado varieties flower and make fruit earlier in their lives than others. Gwen is a variety that is well known for its early fruiting; it will flower the year after it is grafted. So if you buy a small, grafted Gwen tree, you can expect it to bloom the spring after you put it into the ground. (See such a tree in my video profile of Gwen.)
On the other hand, Sir-Prize is a variety that is slower to come into flowering and fruit production. It might take a couple years before a Sir-Prize tree flowers and makes fruit.
All individual trees are different, but on the whole, varieties are more and less precocious. Don’t expect your Sir-Prize to start flowering and making avocados as soon as your friend’s Gwen did.
Varieties also differ in their tendency to produce some fruit every year, although the quantity fluctuates somewhat, or to have years with lots of fruit followed by years with none.
I’ll just use my own Lamb tree as an example. It had zero flowers on it this past spring. Why? Because it was carrying a huge crop of fruit. I’ll harvest that fruit this summer, and then next spring it will most likely flower well and set a crop of avocados that I’ll harvest two summers from now. In other words, it alternates years. It gives flowers and fruit every other year. That’s what Lamb trees around the world tend to do.
You can just be aware of this habit in your avocado tree or you can see my post on alternate bearing for some ways of counteracting it.
Bad leaf burn
After a year when an avocado tree did not receive as much water as it needed, it will show brown tips on its leaves and leaf edges. Sometimes this starts as early as summer, more often it starts in the fall, and it usually worsens into winter. Then in the spring the tree will spend its energy on growing new leaves to replace the burned, damaged ones rather than make flowers.
The solution to this is to water sufficiently such that the tree goes through a full year of growth with little to no brown on its leaf tips and margins. Then it will make lots of flowers in the following spring, provided there are no other obstacles.
Summer heat damage
Extremely high temperatures during summer can cause an avocado tree to not flower, or to flower much less, the following spring. This happened to some avocado trees in Southern California after a nasty heatwave in early September of 2020, when temperatures reached 115 in many inland locations.
Such high temperatures burn the tips of branches on a tree; the heat essentially fries the outside of the tree’s canopy. Unfortunately, this is the flowering wood that has been fried. It is at and near the tips of branches on the outside of an avocado tree’s canopy where it makes most of its flowers.
So trees that were badly burned in September 2020 had almost no flowering in the spring of 2021. They had to grow new flowering wood through the summer of 2021 and could then be ready for flowering in the spring of 2022.
(There are numerous ways to protect avocado trees from high heat, as explained in my post, “Protecting avocado trees from heat.”)
Winter cold damage
Freeze damage in winter is similar to heat damage in summer in that it prunes off the tips of branches that would be flowering the following spring. Like with summer heat damage, the tree needs a year of growing to make new flowering wood. So after a winter with bad cold damage, you can expect flowering in the second spring.
I’ve thrown a lot of ideas at you in this post. My hope is that if you’ve got an avocado tree that is not fruiting or not fruiting much, some of these ideas will strike you as plausible explanations for your tree’s poor performance. And remember that it’s possible for multiple causes to be colluding in order to keep your tree from fruiting well.
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