Alternate Bearing as Survival: Why a Fuerte Tree Floods the Forest With Fruit
Our favorite Fuerte tree is absolutely loaded this year. There is fruit just about everywhere you look. Next year, if she behaves like a Fuerte, she may carry something like 80% less.
That swing is called alternate bearing, and Fuerte is famous for it. There are a few reasons it happens, but one of them is genuinely fascinating: in the wild, a boom year is a survival strategy.
What is alternate bearing?
An alternate bearing tree sets a heavy crop one year and a light one the next, back and forth. Plenty of fruit trees do it to some degree, and avocados are well known for it. Fuerte is one of the most pronounced: the UC Cooperative Extension growers’ handbook, Avocado Production in California, notes that Fuerte groves usually swing even more than Hass groves, and that Fuerte fruit set is erratic. Those uneven crops are part of why California’s growers moved from Fuerte to Hass, which passed Fuerte in volume in 1972. We tell that story in why Fuerte lost California to Hass.
For a grower, the practical effect is simple: you cannot look at this year’s crop and assume next year’s will match.
Why would a tree do that on purpose?
Imagine this Fuerte was not being managed by us at all. It is just a tree growing wild somewhere in the avocado’s native range, which runs from southern Mexico through Central America and the West Indies. (Fuerte itself traces back to a backyard seedling in Atlixco, in the Mexican state of Puebla, found in 1911.)
Animals eat avocados. If the tree set a modest crop every year, the local wildlife could reasonably eat most of it, year after year, and very few seeds would ever get the chance to sprout. But if the tree puts out an enormous crop in one year, there is simply more fruit than the local animals can possibly eat. Some of it drops to the ground, and some of those seeds grow into new trees.
Biologists call this kind of strategy predator satiation, and it is one idea about why the habit exists rather than a settled fact about avocados: overwhelm the eaters, and the leftovers survive. It is a way for the tree to protect itself and make sure its line carries on.
The other reasons
Survival is not the only explanation, and in the grove the mechanics matter more. The handbook explains it through the way avocado shoots grow: spring shoots that come out of flowering shoots which set fruit do not produce flowers the following spring. So a tree carrying a heavy crop has far fewer shoots able to bloom next year, and that is the cause of the light crop that follows. Whether the tree’s stored energy also plays a part is, by the handbook’s account, still not well understood.
Weather can start the cycle in either direction. A spring that is bad for fruit set can cause a poor year, and a spring that is perfect for set can produce a bumper crop that sets up a bust. Cold bloom weather is especially hard on set; the handbook notes that below about 60°F there may be no fruit set at all. In a managed grove all of this matters, because a boom year can set up a bust year whether we like it or not.
Growers do have one lever. In a UC trial reported in the handbook’s second volume (Lovatt, 2001), trees that got an extra dose of nitrogen in April produced about 31% more fruit over four years than the standard program, and the April dose significantly reduced alternate bearing. It is one trial, and timing nitrogen is still debated, but it shows the swing is not entirely out of a grower’s hands.
A heavy crop also brings its own work in the meantime. Branches that are loaded with fruit can sag or break, which is why we stake avocado tree branches in a year like this one. Older Fuerte trees in particular need attention to their structure, which we wrote about in Fuerte tree care for aging trees.
What we do with a loaded year
We cook. With this much fruit, we have been creating a lot of new avocado recipes, and there is a new one coming out every week. If you want a sense of how Fuerte tastes next to Hass and the other varieties, our guide to avocado varieties and how they taste is a good place to start.
A boom year is the time to try a Fuerte. Our 4lb Fuerte box ships when the trees are bearing, picked the week it goes out — and in the lean stretches, you can join the waitlist on the page and we will let you know when fruit is back.
This post is part of our guide to growing avocado trees.
