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Oak trees keep dropping acorns this fall. Here’s how a ‘mast’ year impacts North Texas

Scientists are still unsure what triggers a mast year, but there are a few theories as to why trees produce a big crop of acorns.

If acorns keep fallin’ on your head this fall, you’re likely one of many Texans getting struck by a natural phenomenon.

Oak trees in North Texas are producing an abundant amount of acorns this year due to an organic, cyclical occurrence known as “masting.” During a mast year, acorn-producing trees, or oak trees, can produce anywhere from hundreds to thousands of nuts.

Unlike pecan trees that reliably mast every other year, oak trees are a little more unpredictable, said Mike Arnold, professor of landscape horticulture at Texas A&M.


“Most oaks will have a few acorns every year, but they have prodigious quantities, only cyclically every few years,” Arnold said. “It depends on the species and environmental conditions. It may be kind of an every other year thing, or it may be several years in between.”

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While it’s unclear what exactly triggers a mast year, ecologists theorize environmental factors favor why trees produce a large crop some years.


“We’ve been hunting this down scientifically for years and have never been able to really nail it down,” said Karen Woodard, forester with the City of Dallas.

Rainfall and the favorable temperatures might contribute to the growth and maturity of acorns, Woodard said. But weather conditions don’t necessarily account for their production — it really comes down to the genetic code of each tree.

“Every tree has different genetics,” she said. “You don’t know what tree pollinated the seed on what tree.”


This season, local ecologists noted red oaks and live oaks in the region produced more acorns than usual, which can impact the ecosystem.

How does a mast year affect wildlife?

In general, masting oak trees are good for many animals, including squirrels, geese and deer who feast on the protein-packed nut before hibernating, Arnold said.

“Masting trees can be really important for wildlife because if they’re a hibernating species, they may engorge or eat a lot in the fall to gain fat reserves to get them through the winter,” he said.

In addition to gaining a layer of fat from feasting on acorns, squirrels also store the nuts in the ground for use in the winter.

Excessive acorns can also be somewhat problematic, especially with a large amount of white-tailed deer living in Texas. More deer can also mean more Lyme disease and other pest issues.

“There’s a number of things that could go wrong if we have too many deer,” said Kimberlee Peterson, woodland ecologist at Texas A&M Forest Service. “So there’s a good balance: Nature knows how to balance itself out.”

But why do acorns fall?

Premature acorns falling from trees are a separate phenomenon from masting. This can occur during an ‘on’ or ‘off’ production year.


Acorns drop maturely from masting trees in part due to extreme weather, Peterson said. In general, a lack of rain and sunlight can have an adverse effect on crops.

North Texas is no stranger to extreme weather conditions, with a drought plaguing the region for most of the summer and an early cold front settling over the region in late October. Such factors put a strain on a tree’s ability to produce fruit and result in green acorns littering the ground.

“Whenever trees go under severe stress, they do not produce their fruit all the way, so it won’t fully mature, and we’ll see premature ones drop,” she said.

In short, trees expend a considerable amount of energy to produce acorns, Peterson explained. They receive food through water and nutrients by opening their stomata, or small pores on their leaves, while producing fruit.


“Whenever they’re under severe stress, (trees) actually close their stomata,” she said. “They’re not bringing up the water and the nutrients like they should be, so they’re not getting the energy they need to really produce those acorns.”

What should you do if you see acorns?

Like most things in nature, try to leave them alone. Acorns are a food resource for animals, so it’s best to not pick up too many of them, Peterson said.

Some people will paint acorns and use them as holiday decor, which is fine so long as they’re still leaving some out for squirrels and other wildlife.


Others complain about the amount of acorns in their yard and will want to get rid of their oak trees, Peterson said. The best solution is to rake the acorns and leave your yard as is.

“A lot of people see acorns on their trees or in their yard, and they’re like, ‘oh, it’s all messy,’ and it’s just like, well, it’s a tree, and it’s nature.”

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