About Those Acorns

Fall is a time for nuts and no nut is more noticeable than the acorn, the fruit of oak trees and food of wildlife.

Some years are boom years for acorns. Hikers dodge falling acorns and balance on trails that seem to be covered in marbles.

Other years, we seem to have no nuts.


Like many trees, oaks have irregular cycles of boom and bust. Boom times, called “mast years,” occur every 2-5 years, with few acorns in between. But the why and how of these cycles are still one of the great mysteries of science.

Scientific research can tell us what a mast year is not. A mast year is not a predictor of a severe winter. Unfortunately, plants and animals are no better at predicting the future than we are.

Strangely, mast years are not simply resource-driven. Sure, a wet, cool spring can affect pollination and a hot, dry summer can affect acorn maturation. But annual rainfall and temperature fluctuations are much smaller in magnitude than acorn crop sizes. In other words, weather variables cannot account for the excessive, over-the-top, nutty production of acorns in a mast year.

So what does trigger a mast year? Scientists have proposed a range of explanations—from environmental triggers to chemical signaling to pollen availability—but our understanding is hazy and the fact is that we simply don’t know yet.

Boom and bust cycles of acorn production do have an evolutionary benefit for oak trees through “predator satiation.” The idea goes like this: in a mast year, predators (chipmunks, squirrels, turkeys, blue jays, deer, bear, etc.) can’t eat all the acorns, leaving some nuts for growing into future oak trees. Years of lean acorn production keep predator populations low, so there are fewer animals to eat all the seeds in a mast year. Ultimately, a higher proportion of nuts overall escape the jaws of hungry animals.

Whatever the reasons and mechanisms behind acorn cycles, mast years do have ecological consequences for years to come. More acorns, for example, may mean more deer and mice. Unhappily, more deer and mice may mean more ticks and, possibly, more incidences of Lyme disease.

Many animals depend upon the highly-nutritious acorn for survival. Oak trees, meanwhile, depend upon boom and bust cycles, and a few uneaten acorns, for theirs.

Amazing Acorn Facts

  • There are about 90 species of oaks in North America. All oaks have acorns.
  • There is no such thing as an Acorn Tree.
  • Acorns belonging to trees in the Red Oak group take two growing seasons to mature; acorns in the White Oak group mature in one season.
  • Oak trees have greenish, inconspicuous female flowers and are wind pollinated.
  • Oak trees of North American annually produce more nuts than all the region’s other nut trees together, wild and cultivated.
  • One huge oak can drop up to 10,000 acorns in a mast year!
  • Masting takes a lot of energy! Oak trees grow slowly in a mast year and grow well the year after.

Photo credit: beautifulcataya via photopin cc

36 thoughts on “About Those Acorns

  1. Mary

    I live in an oak forest in northern Virginia and have lived here for 36 years. Last fall there were very few acorns, but this fall is a banner year for acorn production. However this year there are almost no squirrels to harvest all these acorns. I first noticed the declining squirrel population this past summer.

    We have had plenty of these sorts of feast and famine acorn autumns in the past, but this is the first year the squirrels have abandoned fort.

    The birds are having a field day, but what gives with the squirrels?

  2. Kevin Jensen

    My summer home in Barry County Michigan has 4 very large oak trees and this year it must be having a mast year (2014) this is my firs year owing the home and my first time pulling up to the home after the acorns have fallen my son fell as soon as he stepped out of the car our entire yard was covered with acorns. Do I need to rake all of them up before spring? Will they produce more oak trees to grow if I don’t rake them? I would say that a minimum of 40,000 have fallen in my yard this year.

  3. Steve Simons

    I have a well groomed yard and hire an arborist to crown my trees. After five years of living in peace, my neighbor is demanding that I cut down a healthy mature oak tree. He wants me to sweep up any acorns that fall on his property, to sign a note that I will pay for his house if the tree falls on it (he says that exposed roots are a sign a a shallow tree that will topple; and says that I am responsible for the dents on the hood of his car that are a result of a mast year before I bought the house. Please advise. I live in Maine and purchased this house because of the beautiful oak trees.

    1. Vickie

      I live in Maine as well. Not sure where you are, but usually going to the town office and explaining your situation to a town manager or constable could be helpful. Unless your town has a specific ordinance prohibiting oaks and acorns I am pretty sure your neighbor has no leg to stand on. Now, if your tree did fall on his property you would probably have to saw it up and take it away (burn it in your woodstove) . If it damaged any of his property I am pretty sure he would have insurance to take care of it. I think it is considered an ‘act of god’. Good luck.
      I came to this site looking to find out what the time frame of normal is for acorns falling. I have this feeling that we are headed for an early fall since the acorns usually (as far as my memory serves me) they fall in Sept. and October. How long have you had your oak and when does it usually drop its acorns?

      1. LWos

        You better check with your Homeowners Insurance Agent. Your neighbor has ” put you on notice” so if a rotted limb overhanging his property did come down and cause damage to his home, his property etc, he could sue you for damages.

        As for acorns………. I’ve lived on my Mid Michigan property for 25 years and have only seen one other year that the Oaks have produced so many. Last year hardly any fell but we had a lot of Acorn Plum Galls drop.
        I am surrounded by massive old oaks, both the red and white variety, and they are dropping them by the thousands. My lawn is covered with them and it’s like walking on a bed of marbles. I also have a brand new Ford Flex that sits outdoors 24/7/365 and cringe ever time one of the acorn’s hit is. It sounds like someone firing a shot when they hit. So far, no damage but If I were you, I’d take photos of his car IN THE EVENT he already has damage on it and then tries to claim your trees are the cause and he warned you.

  4. She Granfield

    I was researching this subject and came upon the Mass Audobon website. I have no acorns this year and thought that was very strange. Last year we had alot of acorns. My yard if loaded with Oak trees and so are my neighbors. Others in my East Longmeadow, MA area are saying the same thing. No Acorns. but we had a tornado, hurricane and devastating winter storm in 2011. Could that be why?

  5. Russ Cohen

    Hi Everyone – yes, it is true that Native Americans (and many other indigenous peoples) ate (and still eat) acorns, typically leached, ground into a meal and then cooked. While I have been teaching people about acorns and other edible wild plants since 1974, I have recently observed an uptick in interest in people wanting to know about how to process and eat acorns. Maine-based forager and expert botanist Arthur Haines likes to (and teaches others how to) collect, process and use acorns from the “Red Oak” group, while I prefer gathering and using the (usually) less bitter acorns from the “White Oak” group.

    Here’s a link to a YouTube video where I (preceded by “Wildman” Steve Brill) describe how to process and eat acorns (http://www.youtube.com/watch?v=i7Vj4iU-taU&feature=channel&list=UL) ; and here’s a link to the recipe section of my web page, which has a yummy recipe for “Fall Harvest Muffins”, utilizing flour/nut meal made from White Oak acorns (http://users.rcn.com/eatwild/recipes.htm).

    — Russ Cohen

    P.S.: I would say this has been a “medium” year for acorns in southern New England – not as many as a true “mast year”, but way more than the scarcity of acorns last year.

    1. Kristin

      Thanks, Russ, for all this great information. Is any of this information — about acorns and/or milkweed — in your wonderful book “Wild Plants I Have Known . . . and Eaten?” (Unfortunately, I don’t have a copy with me to check.) Thanks!

      1. Russ Cohen

        Hi Kristin – thanks for the favorable mention of my foraging book (see, e.g., http://identifythatplant.com/foraging-resources/russ-cohen), which (in case anyone is interested) is available from (and all proceeds from its sale benefit) the Essex County Greenbelt Association (http://www.ecga.org/store).

        The book does have an entire chapter devoted to eating Milkweed, along with a yummy recipe for “Milkweed Egg Puff”, which tastes like a cross between a souffle and a casserole.

        While my book contains some info about eating acorns, I did a more extensive writeup about processing and eating acorns that appeared in Greenbelt’s newsletter back in the summer of 2004. While I don’t think an on-line version of that document exists, I can supply anyone interested with a photocopy of it – let me know at eatwild@rcn.com if you would like one.

        — Russ

  6. Kathleen Spaeth

    Our Red Oak Trees, here in Tyngsborough, MA have produced and dropped many acorns this year. I would say that they are much larger, and more of a plentiful amont, than any other year that we have lived here (we have been living here for 6 Falls now). Also, these Trees have attracted our two “resident” Porcupines that have climbed into them, high enough to stay away from the Fischer Cats (who are their known predators), and been eating the upper branches and then dropping them down onto our side yard (to my Husband’s chagrine).

  7. alice gabriel

    We have a 2nd home in Newfield ME, southwestern part, and two years ago our oak trees had lots and lots of acorns. Last year there were almost no acorns, but there were lots of pine cones. This year we again have lots and lots of acorns!! The yard is totally covered, altho by this time many of the actual nuts are gone and just empty caps. Lots of chipmunks and squirrels around!! It is interesting that nature has provided food for the animals acorns one year and pine cone seeds another.

  8. Stephen B.

    Here at the residential school in Walpole that I work at, we collected several hundred red oak acorns from several trees in our forest this past fall. I’m going to hold these acorns in cold storage this winter and then plant them in a garden transplant bed this coming spring and see if we can grow some seedlings for eventual transplant around other parts of the forest, and maybe the school buildings as well. I think nurseries such as New Hampshire’s state forest nursery give red oaks two years in a transplant bed and that is our plan too.

    I have read that red oak group acorns sprout the following spring after they fall from the trees and have to stratify in cold weather over the winter first, this as opposed to white oak family acorns that sprout shortly after falling in the fall.

    Anyhow, we didn’t have any trouble finding lots of acorns under the several trees we gathered from, but with regards as to whether this could be considered a mast year, in all honesty I haven’t myself collected acorns for replanting before and I cannot say whether the trees usually produce this many acorns, or they produce more or less in other years.

  9. Carolyn

    I’m in Mashpee on the Cape and it appears to be a mast year here….at least in my neighborhood. We have lots of squirrels (gray and black) and chipmunks. They are very busy.
    Standing still on our deck and you can listen to falling acorns.We have to sweep our driveway about twice a week due to the fallen and half-eaten acorns.
    Last year, we had next to none.

  10. Diane

    Here in Rockport the oaks in our yard have almost no acorns this year. Other years we have lots! Did have many small worms, hanging from webs in the Spring. Would they cause harm to the trees so they don’t produce as many nuts? The leaves were certainly eaten by them.

  11. Julie

    Is this a “mast year”? I’ve not seen many acorns at all here in Canton and I’m overrun w/oaks, but perhaps it’s early yet…

    1. Kristin

      We seem to be experiencing regional variation this year. The Cape is reporting a mast year. Here in central MA, I’m seeing some acorns but not large quantities. The only thing I can say with certainty is that last year was a “no acorn” year for just about everyone and this year we’re experiencing moderate acorn levels.

      Anyone else have other reports from around the state and beyond?

  12. Diane

    We have lots of oaks and we have a tar and gravel roof with a gentle slope. In the spring, there is one particularly industrious squirrel who runs up the dogwood and jumps to the roof to harvest the acorns that have wintered over on our roof. Mind you, there are tons of acorns on the ground. They must toast just right in the sun to be the most flavorful, because he brings one down, hides it and goes back up for another. The squirrel makes many trips each day!

  13. Amy Helling

    Is it a mast year only for a single tree, or for a single type of oak, or for all oaks in a geographic area? If not the last, I don’t see how satiation would work, since about half to one-fifth of all oaks would be having a mast year in any particular year, and the rest would not. Presumably this would mean that the animals that eat acorns would not have to deal with much variation from year to year. But if it affects all oaks in an area, what are the spatial boundaries to the effect?

    1. Kristin

      These are excellent questions and you are right: individual trees do not mast. It is a group effort and somehow trees manage to synchronize their seed production. It’s amazing and still something of a mystery; however, the best article I’ve seen on the subject is “The Mystery of Masting,” written way back in 2005 and available here:
      Hope it’s helpful in answering at least some of your questions.

  14. Valerie White

    a naturalist at Moose Hill told me acorn yield fluctuation was an adaptation of the trees to suppress populations of a weevil.

    1. Kristin

      The acorn weevil — a type of beetle — is one of my favorite creatures to observe in the fall. If you collect a handful of mature acorns and smash them open with a hammer, you may see a white, grub-like creature in some of them. That’s the larva of the acorn weevil. It will feed inside the acorn until mature and then, after the acorn falls, the acorn weevil larva will drill a hole in the acorn, emerge, and spend the winter in the soil. It does seem likely that the acorn weevil is one of the many acorn “predators” that drives the boom/bust cycle of oak trees.

    1. Kristin

      Yes, Native Americans of both East and West used acorn for flour and other foods. My neighbor, an Abenaki, still collects acorns in large sacks and suspends them in a local stream for several weeks to leach out the bitterness. After that, the acorns can be roasted or ground into meal for bread. Historically, acorns were a staple food for humans and an important source of fat and protein in winter.

      1. Kristin

        This is fun to read acorn observations from around the state and beyond. There seem to be some regional variations, but acorns are definitely more plentiful than last year everywhere.


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