About Those Acorns

Photo credit: beautifulcataya via photopin cc

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

66 thoughts on “About Those Acorns


    what kind of oak tree sheds loads of small uncapped acorns in the summer then large capped acorns in the fall

  2. Penny FIsh

    Why do the caps of the acorns sometimes remain attached on the oak trees after the acorn nut falls?

  3. Pam

    Last year was a mast year– thousands of acorns. This year none. Thanks for your article. We are no longer worried about the tree. Now we’re worried about the squirrels being hungry. We’ll put out something for them.

    1. b0bb0

      We have two enormous, healthy pin oaks, one in the front and one in the back. This year the front oak had fewer acorns than usual. The one in the back had the most we’ve ever had. I filled three 35 gallon garbage cans. I left a lot more behind since they were embedded in our muddier than normally muddy yard. They are now sprouting!
      It is obvious that the timing of a mast year can be different in different trees in the same environment.

  4. Jean

    I have been looking for info on sprouting acorns. Reds, whites, pins, and burrs. I have a huge white oak next to my house and it drops and sprouts nice acorns almost every fall. Hundreds send down tap roots about ten inches. In the spring about a dozen come up and most die by the end of the year even if watered occasionally. The rabbits? like to nip the tips off of them too. I have yet to have one make it thru the NE Iowa winter.
    I’ll put several questions out there.
    Are the parent trees preventing the sprouts from succeeding within 50ft or so radius of it?
    If trying to sprout in containers, which end of the acorn needs to be pushed how far down?
    What is required to hold over reds, etc. to sprout the next spring or fall?
    Do the acorns not dry out like whites do?
    What kind of containers to use for long tap root but conserve space? Paper towel rolls, pieces of pvc pipe, rolled up plastic sleeves, etc.?
    Any ideas, tips, and advice would be greatly appreciated.

    1. Robert Pogson

      White oak seedlings die in shade. Move them out from under the parent and they will thrive. Another thing that kills them is drought before they get that magnificent tap root down deep.

  5. robert bacjand

    Thanks for getting right to the point.

    In 2015, I gathered dozens of hearty looking acorns from beneath a grandson of the famous Charter Oak tree that stood in Hartford, CT until it fell in a storm in 1853 or so. This particular tree has documented lineage back to that time, and is now around ninety years old itself. It had been planted in a nearby cemetery in 1933.

    Unfortunately, I guess I put them outside (still in pots) too soon after sprouting because the squirrels came and devoured them.

    So I went back to the cemetery in 2016, and there wasn’t an acorn to be found. I just went again this weekend and still nothing…except for some tiny acorn-like looking caps with even tinier buds attached to the caps. Not sure if they are or aren’t; maybe a precursor to a better yield next year?

    As it stands now, I believe this cemetery descendant is the last documented still living of the Charter Oak line. I’ve got a great spot picked out on some protected land trust acreage managed by a local nature conservancy, and I’d really like to see two or three great-grandsons taking root there.

  6. Chrys

    Thank you for taking the time to post this. I came looking for info on why an oak which usually produces acorns in varying amounts every year for the last 12 years would suddenly not produce any. Last year was a major boom year with at easily twice the acorns it usually throws. This year absolutely none. Although this article didn’t answer my question outright – I did learn something. I remain a tad concerned about my big old pin oak… especially because of it’s proximity to the house. Other than the leaves having more gauls than usual this year there don’t seem to be any other visible symptoms of disease.

  7. Sealdoc

    Thanks for all your responses. I thought I had a rodent in my attic.
    But I realized don’t really have a attic. I live in a mobile home. Been
    Here 13 years, never had that kind of noise before. Some sound like
    22 riffle going off, and my roof is shingled.
    Didn’t even cross my mind about the huge oak behind my house.
    Probably less than 15 feet. I guess with what little rain we’ve had
    Caused them to fall premature. Thanks forum for making me fill
    So dumb. Lol.

  8. dave powell

    Hello we are in rural pei
    Canada we planted a red oak some 30 years ago and in spite of good growth there are no acorns!!!!! Does anyone know why??? Thanks

  9. Virginia

    I live in South Texas and one of my Oak tree has dropped thousands of acorns. I have ten trees about 38 years old. Others have not dropped any. Are some male or female trees?
    Whereas some do have acorns and others don’t. (Dumb question). Anyhow, I can’t keep up with either their acorns falling then all their leaves falling. Either one thing or another. I love my trees but I can no longer keep sweeping, raking, blowing or picking acorns or leaves from my drive way or carpet grass. If I don’t blow them from my drive way my car or other cars smash them and they stain my black drive way or concrete drive. What a mess! Next I’ll try the vac and see how that works. I will never recommend this tree for a yard.

    1. Trish

      Your problem sounds just like mine. Nuisance tree for sure. I moved from California to New Mexico. Wanted a small yard with no upkeep. I didnt look up an question that pretty tree in my front yard that requires constant cleanup.

  10. Jw

    Apparently the passenger pigeons used to follow the mast years of oaks around North America. People wouldn’t see them for years, the bam-blacked out skys of pigeons and acorns everywhere. People didn’t believe that they went extinct, just that they were in some other state following an acorn bumper. I guess the passenger pidgeons could predict them.

  11. Jon Miller

    I live in SE Louisiana and this year (Q3 2015) is a mast year for my 80+ yr old white oaks. I’m glad to read that its not a predictor of a cold winter. Our house has a metal roof which the oaks overhang. Sometimes its a cacophony!

  12. Marty

    Came across this posts while looking in my back yard and wondering where all the acorns are. Last year (2014) must have been a mast year for the oaks on my property. I have 2 100+ year old oaks and last year the amount of acorns that fell was baffling. Easily tens of thousands from the two trees. This year however, there were far less. On of the big problems that I have is the amount of squirrels that come to feast on and bury the acorns on my property. Last year, I was able to snap a picture (with my phone, not some wide angle lense) and capture 23 squirrels in one photo. They make such a terrible mess too, but I guess they are just benefitting from the abundance. I live in southern Quebec, Canada, just iutside of Montreal.

  13. Tony Costelloe

    Interesting article. I’m in Grand Rapids, Michigan and have 100 year old red and white oak trees close to my house. I’ve been here 15 years and I’ve never seen an acorn drop like this year. I’ve been raking up and taking away wheel barrow loads. Clearly a mast year. I’m curious about the this cycle so I’ll keep track of the drop in future years.

    1. Robert Pogson

      You are so lucky! I suggest drying or freezing white oak acorns to spread the bounty over several years. They are good food for people and critters. Grind them to feed smaller birds over winter. If not dried/frozen they will sprout and spoil.

  14. Brian Greca

    We’re in central Connecticut and this year’s acorn production is out of control! I think I’m going to try the Shop-Vac trick, as there’s no other reasonable way of collecting these things.

  15. Diane

    I have an oak that drops acorns on my roof. What I notice is that when the sun goes down they slowly stop dropping acorns till it gets dark. Why is that? I’m wondering if it’s the temperature drop. It’s kind of nice to be able to sleep without acorns hitting the roof all night. Thank you.

    1. Elmer fudd

      Shhh be very very quiet the squirrels are sleeping though when the sun comes up they will be acorn hunting.?

  16. Lisa Meyer

    23 years ago we planted a red oak in the front yard of our Columbus, Ohio home. Since that time we’ve had 2 incredibly crazy mast years, including last fall. I’m talking thousands and thousands of acorns. These years kill the grass, dent the cars, hurt your feet and are dangerous for anyone using the front door. The acorns are very difficult to pick up. I tried raking and used the neighbor’s leaf blower/sucker, but nothing was very effective. Finally I dragged our super heavy duty shop vac out of the basement and yes, I vacuumed the yard. It worked great! This spring and summer I can actually walk comfortably barefoot in the front yard after lasts fall’s super mast year.

  17. 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?

  18. 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.

  19. 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.

    2. Rosemary

      We have the same situation with our neighbors. They want us to cut the top of our three trees off. We trimmed them recently but this year is a bad year for acorns. Not sure how to resolve. Let me know of any ideas. We love our trees and Don’t want to cut !!!

    3. Jim

      I know this over a one + year old post, but I live in NW Indiana and own a two acre property with 17 mature red and white oak trees ( some are 200+ years old) in the expansive yard. I love my oak trees and do everything not to impede their health and existence. That includes trimming large overhanging and threatening branches, but am careful not to over trim them. Your reference to exposed roots doesn’t indicates they are shallow. Oak tree roots grow downward, but doesn’t mean there aren’t smaller off shoots from those big roots. Pine and deciduous trees have shallow root systems. They’re just seeking water. Don’t know what to tell you about your neighbor, except maybe he/they should move to the city, if he/they are not tree lovers. I would make sure you have sufficient liability insurance, in the event something does happen to your tree(s) one day to protect you and your oak tree hating neighbor. I consulted my local DNR forester to evaluate my trees and he did so at no charge.

      Feel free to reply, if you wish.

      1. Tina

        Topping trees is considered bad practice. It weakens the trees. Selective pruning of limbs is preferred. Jim is correct about the oak roots growing downward. Unfortunately, where I live in NJ, the roots can only grow down to about 18 inches. In addition, because of shading, most of the trees in our wooded yard have no lower limbs, making them top heavy. As a result , we have had several oaks uprooted by microbursts of wind, and the root balls are much smaller than expected for the size of the tree. We cut down one oak that was very close to and leaning over the house and had dropped a large limb that just missed our house. We also selectively trimmed another nearby oak. All the trees in our yard lean toward the house because that is where the open light is. That being said, I would not cut down a healthy oak unless it was necessary, and that would depend on your specific circumstances. Your local state extension office may be able to provide you with more guidance if you bring them pictures and information.

    4. Irene

      Steve, DO NOT SIGN ANYTHING! In MA, an abutter has the right to cut back branches of a neighbors tree, so long as it doesn’t kill the tree, if the neighbor doesn’t like the branches/leaves/acorns/roots on their property. (You would likely be trespassing and subject to paying for any damages if you lopped off a bunch of branches so that they fall in your neighbors yard, and would have to trespass to retrieve the cuttings). In MA long as you maintain your trees – which could be nothing more than regularly checking them, or having an arborist inspect them – if one falls on a neighbors property their homeowners insurance covers it. I suspect Maine’s laws are similar to MA laws. Just put “Maine” and “tree laws” in a good search engine and you will find the information on Maine’s laws. Of course, you may not want your neighbor hacking off limbs of your trees (they can only cut to the property line), but you could let the neighbor know that while it is not your responsibility, you would be happy to do that as a neighborly thing if the neighbor signs a release allowing you to do so and without recourse – in other words, the neighbor has to agree not to sue you for any damages while you are on the neighbor’s property performing this neighborly service. That way your arborist can make the cuts in a manner that will preserve your beautiful trees!

  20. 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?

  21. 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 [email protected] if you would like one.

        — Russ

  22. 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).

  23. 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.

    1. George Boettner

      East Orleans was hard hit by both winter moth and gypsy moth in some areas. Even partial defoliation can encourage a tree to abort its crop to put energy back into the roots and re-leafing. Black oaks on the Cape are also being hard hit by a new oak gall wasp, which can severely impact trees as well. I n addition a lot of the oaks on the Cape are white oaks, so the flowers in spring produce acorns this fall, whereas in the black oaks, the flowers in spring 2014 produced the fall 2015 crop. Often the Cape will heavily mast its white oaks in different years than western MA (which is more red/black oak). A big black oak crop this year could be related to the amount of water available in 2014, whereas white oaks are responding only to this years rainfall. So lots of things can impact a local tree.

  24. 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.

  25. 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.

  26. 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.

  27. 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?

  28. 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!

  29. 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.

  30. 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. Jan

      On Cape Cod the first ones were so tiny! Now bigger ones, but no huge harvest, unlike some years…


    2. 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. Fred Fellner

      It is certainly a mast year in Baton Rouge, Louisiana! The live oaks are unbelievable in production.

      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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