Why are there so many acorns this year?

2021-12-29 06:44:13 By : Mr. Jacky Cai

More than a few inquiries to our Master Gardener Help Desk have asked why there appears to be so many acorns this year compared with last year. Turns out, this phenomenon is not limited to this year, and humans have been intrigued by this event for millennia.

Oaks and other forest tree species do occasionally produce enormous amounts of seeds. This is called “masting” or a “mast event.” In a mast year, trees will produce more fruit than normal. The term “mast” comes from the Old English word, mæst, which referred to forest tree nuts that accumulated on the ground, especially nuts that were used in fattening domestic pigs and were food resources for wildlife (like acorns). Mast events are periodic and in the case of many oak species, a large mast event may happen every two to five years, depending on the species of oak. These events may be preceded and followed by small or moderate acorn crops or no acorns at all.

So why does masting happen? Masting is not an individual tree phenomenon but instead happens at the group or population level where the group of trees are in sync on how much and when to produce fruit. How do they do this? Well, that’s where there is still some uncertainty. One explanation is that environmental conditions signal the trees on how they will distribute their energy resources year to year. The production of a huge volume of seed, like acorns, requires a lot of energy from the tree. When oak trees have favorable weather at the time of oak flowering (remember all that pollen in the spring?) and good growing conditions, this can be a cue that it is a good year for a masting event. Unfavorable weather, such as a late freeze, high temperatures, or drought during pollination and seed development, on the other hand, can prompt trees to limit resources to seed production. However, well-timed favorable environmental conditions are not the whole story.

The year following a mast event, regardless of environmental conditions, trees will often produce less fruit. Suggesting that the energy trees put into producing a large fruit set one year means forgoing production the next. Basically, there is a growth versus reproduction tradeoff, and trees that shift resources to flower and fruit production one year will not grow as much in that same year compared to other non-mast years. But what advantage is this to the tree? Why not split resources equally between growth and fruit production every year?

During a normal year, most acorns may be consumed by wildlife, and there may be few seeds that are left to germinate into oak seedlings. But during a mast event, seedeaters may not be able to eat all the acorns being produced and the surplus of acorns will become seedlings, guaranteeing another generation of oak trees. When you put it all together -- the environmental cues, tradeoffs, and seed predators – the picture that emerges is that mast events allow trees to provide a viable crop of seedlings every few years when environmental conditions are conducive for optimizing fruit production and seed germination.

Of course, the humble acorn doesn’t stop there. Since it is an important food for many animals, masting events will influence wildlife populations in years after an event. And more acorns, certainly means more squirrels.

To learn more about managing your Florida landscape, reach out to UF/IFAS Extension Alachua County’s office to speak with a Master Gardener Volunteer at (352) 955-2402 or mag@alachuacounty.us or visit Alachua County’s Florida-Friendly Landscaping Program webpage at https://bit.ly/AlachuaFFL.

 — Dr. Cynthia Nazario-Leary is the Environmental & Community Horticulture Extension Agent for UF/IFAS Extension Alachua County. Contact her at cnazarioleary@ufl.edu or 352-955-2402.