The acorn, or oak nut, is the nut of the oaks and their close
Quercus and Lithocarpus, in the family Fagaceae). It
usually contains a single seed (occasionally two seeds), enclosed in a
tough, leathery shell, and borne in a cup-shaped cupule. Acorns are
1–6 cm (0.39–2.36 in) long and 0.8–4 cm
(0.31–1.57 in) broad. Acorns take between 6 and 24 months
(depending on the species) to mature; see the list of
for details of oak classification, in which acorn morphology and
phenology are important factors.
1 Ecological role
1.1 Dispersal agents
2.1 As food
2.2 Use by Native Americans
2.3 In culture
2.3.2 Contemporary use as symbol
4 See also
6 External links and further reading
Acorns play an important role in forest ecology when oaks are the
dominant species or are plentiful. The volume of the acorn crop may
vary widely, creating great abundance or great stress on the many
animals dependent on acorns and the predators of those animals.
Acorns, along with other nuts, are termed mast.
Wildlife that consume acorns as an important part of their diets
include birds, such as jays, pigeons, some ducks, and several species
of woodpeckers. Small mammals that feed on acorns include mice,
squirrels and several other rodents.
Ponies eating acorns. Acorns can cause painful death in equines,
especially if eaten to excess.
Large mammals such as pigs, bears, and deer also consume large amounts
of acorns; they may constitute up to 25% of the diet of deer in the
autumn. In Spain, Portugal and the
New Forest region of southern
England, pigs are still turned loose in dehesas (large oak groves) in
the autumn, to fill and fatten themselves on acorns. Heavy consumption
of acorns can, on the other hand, be toxic to other animals that
cannot detoxify their tannins, such as horses and cattle.
The larvae of some moths and weevils also live in young acorns,
consuming the kernels as they develop.
Acorns are attractive to animals because they are large and thus
efficiently consumed or cached. Acorns are also rich in nutrients.
Percentages vary from species to species, but all acorns contain large
amounts of protein, carbohydrates and fats, as well as the minerals
calcium, phosphorus and potassium, and the vitamin niacin. Total food
energy in an acorn also varies by species, but all compare well with
other wild foods and with other nuts.
Acorns also contain bitter tannins, the amount varying with the
species. Since tannins, which are plant polyphenols, interfere with an
animal's ability to metabolize protein, creatures must adapt in
different ways to use the nutritional value acorns contain. Animals
may preferentially select acorns that contain fewer tannins. When the
tannins are metabolized in cattle, the tannic acid produced can cause
ulceration and kidney failure.
Animals that cache acorns, such as jays and squirrels, may wait to
consume some of these acorns until sufficient groundwater has
percolated through them to leach out the tannins. Other animals buffer
their acorn diet with other foods. Many insects, birds, and mammals
metabolize tannins with fewer ill effects than do humans.
Species of acorn that contain large amounts of tannins are very
bitter, astringent, and potentially irritating if eaten raw. This is
particularly true of the acorns of American red oaks and English oaks.
The acorns of white oaks, being much lower in tannins, are nutty in
flavor; this characteristic is enhanced if the acorns are given a
light roast before grinding.
Tannins can be removed by soaking chopped acorns in several changes of
water, until the water no longer turns brown. Cold water leaching can
take several days, but three to four changes of boiling water can
leach the tannins in under an hour. Hot water leaching (boiling)
cooks the starch of the acorn, which would otherwise act like gluten
in flour, helping it bind to itself. For this reason, if the acorns
will be used to make flour, then cold water leaching is preferred.
Being rich in fat, acorn flour can spoil or molder easily and must be
carefully stored. Acorns are also sometimes prepared as a massage oil.
Acorns of the white oak group, Leucobalanus, typically start rooting
as soon as they are in contact with the soil (in the fall), then send
up the leaf shoot in the spring.
Sprouting acorn of
Acorns are too heavy for wind dispersal, so they require other ways to
spread. Oaks therefore depend on biological seed dispersal agents to
move the acorns beyond the mother tree and into a suitable area for
germination (including access to adequate water, sunlight and soil
nutrients), ideally a minimum of 20–30 m (66–98 ft) from
the parent tree.
Many animals eat unripe acorns on the tree or ripe acorns from the
ground, with no reproductive benefit to the oak, but some animals,
such as squirrels and jays serve as seed dispersal agents.
squirrels that scatter-hoard acorns in caches for future use,
effectively plant acorns in a variety of locations in which it is
possible for them to germinate and thrive.
Even though jays and squirrels retain remarkably large mental maps of
cache locations and return to consume them, the odd acorn may be lost,
or a jay or squirrel may die before consuming all of its stores. A
small number of acorns manage to germinate and survive, producing the
next generation of oaks.
Scatter-hoarding behavior depends on jays and squirrels associating
with plants that provide good packets of food that are nutritionally
valuable, but not too big for the dispersal agent to handle. The beak
sizes of jays determine how large acorns may get before jays ignore
Acorns germinate on different schedules, depending on their place in
the oak family. Once acorns sprout, they are less nutritious, as the
seed tissue converts to the indigestible lignins that form the
In some cultures, acorns once constituted a dietary staple, though
they have largely been replaced by grains and are now typically
considered a relatively unimportant food, except in some Native
American and Korean communities.
Several cultures have devised traditional acorn-leaching methods,
sometimes involving specialized tools, that were traditionally passed
on to their children by word of mouth.
Acorns served an important role in early human history and were a
source of food for many cultures around the world. For instance,
the Ancient Greek lower classes and the Japanese (during the Jōmon
period) would eat acorns, especially in times of famine.[citation
needed] In ancient
Iberia they were a staple food, according to
Strabo. Despite this history, acorns rarely form a large part of
modern diets and are not currently cultivated on scales approaching
that of many other nuts. However, if properly prepared (by selecting
high-quality specimens and leaching out the bitter tannins in water),
acorn meal can be used in some recipes calling for grain flours. In
Pliny the Elder
Pliny the Elder noted that acorn flour could be used to
make bread. Varieties of oak differ in the amount of tannin in
their acorns. Varieties preferred by American Indians such as Quercus
kelloggii (California black oak) may be easier to prepare or more
In Korea, an edible jelly named dotorimuk is made from acorns, and
dotori guksu are Korean noodles made from acorn flour or starch. In
the 17th century, a juice extracted from acorns was administered to
habitual drunkards to cure them of their condition or else to give
them the strength to resist another bout of drinking.
Acorns have frequently been used as a coffee substitute, particularly
when coffee was unavailable or rationed. The Confederates in the
American Civil War
American Civil War and Germans during
World War II
World War II (when it was called
Ersatz coffee), which were cut off from coffee supplies by Union and
Allied blockades respectively, are particularly notable past instances
of this use of acorns.
Use by Native Americans
Mortar holes for pounding acorns into flour, Lost Lake, California
Acorns were a traditional food of many indigenous peoples of North
America, and served an especially important role for Californian
Native Americans, where the ranges of several species of oaks overlap,
increasing the reliability of the resource. One ecology researcher
of Yurok and Karuk heritage reports that "his traditional acorn
preparation is a simple soup, cooked with hot stones directly in a
basket," and says he enjoys acorns eaten with "grilled salmon,
huckleberries or seaweed." Unlike many other plant foods, acorns
do not need to be eaten or processed right away, but may be stored for
a long time, much as squirrels do. In years that oaks produced many
acorns, Native Americans sometimes collected enough acorns to store
for two years as insurance against poor acorn production years.
After drying them in the sun to discourage mold and germination, women
took acorns back to their villages and cached them in hollow trees or
structures on poles, to keep them safe from mice and squirrels. The
stored acorns could then be used when needed, particularly during the
winter when other resources were scarce. Those acorns that germinated
in the fall were shelled and pulverized before those that germinate in
spring. Because of their high fat content, stored acorns can become
rancid. Molds may also grow on them.
The lighting of ground fires killed the larvae of acorn moths and
acorn weevils by burning them during their dormancy period in the
soil. The pests can infest and consume more than 95% of an oak's
Fires also released the nutrients bound in dead leaves and other plant
debris into the soil, thus fertilizing oak trees while clearing the
ground to make acorn collection easier. Most North American oaks
tolerate light fires, especially when consistent burning has
eliminated woody fuel accumulation around their trunks. Consistent
burning encouraged oak growth at the expense of other trees less
tolerant of fire, thus keeping oaks dominant in the
Oaks produce more acorns when they are not too close to other oaks and
thus competing with them for sunlight, water and soil nutrients. The
fires tended to eliminate the more vulnerable young oaks and leave old
oaks which created open oak savannas with trees ideally spaced to
maximize acorn production.
A motif in Roman architecture, also popular in Celtic and Scandinavian
art, the acorn symbol is used as an ornament on cutlery, furniture,
and jewelry; it also appears on finials at Westminster Abbey.
Contemporary use as symbol
The acorn is the symbol for the
National Trails of England and Wales,
and is used for the waymarks on these paths. The acorn,
specifically that of the white oak, is also present in the symbol for
the University of Connecticut.
Acorns are also used as charges in heraldry.
The word acorn (earlier akerne, and acharn) is related to the Gothic
name akran, which had the sense of "fruit of the unenclosed land".
The word was applied to the most important forest produce, that of the
oak. Chaucer spoke of "achornes of okes" in the 14th century. By
degrees, popular etymology connected the word both with "corn" and
"oak-horn", and the spelling changed accordingly. The current
spelling (emerged 15c.-16c.), derives from association with ac (Old
English: "oak") + corn.
Acorn in heraldry
Acorn waymark for National Trails
Copper acorns at the Peace Palace, The Hague.
Chuckachancy women pause in their work preparing acorns for grinding,
California, ca. 1920
Oak tree in Danish is egetræ. The"g" in egetræ is silent. Acorn
comes from the Old Norse word Egekorn (with a silent "g").[citation
^ Plumb, Timothy R., ed. (1980). Proceedings of the symposium on the
ecology, management, and utilization of California oaks, June 26–28
(PDF). USDA Forest Service General Technical Report PSW-044.
pp. 1 to 368. ASIN B000PMY1P8.
^ King, Richie S. (2 December 2011). "After Lean
Acorn Crop in
Northeast, Even People May Feel the Effects". The New York Times.
Retrieved 4 December 2011. there is nothing unusual about large
fluctuations in the annual number of acorns.
^ "Acorns fatally poison 50 ponies in English forest".
Horsetalk.co.nz. 2013-11-27. Retrieved 2017-01-06.
^ "ACORN POISONING – Are Acorns Poisonous To Horses?".
Horse-advice.com. Retrieved 2017-01-06.
^ "Acorns, Oaks and Horses:
Tannin Poisoning". The Way of Horses.
2002-09-15. Retrieved 2017-01-06.
^ Barrett, Reginald H. (1980). "Mammals of California Oak
Habitats-Management Implications". In Plumb, Timothy R. Proceedings of
the symposium on the ecology, management, and utilization of
California oaks, June 26–28 (PDF). USDA Forest Service General
Technical Report PSW-044. pp. 276–291.
^ "A bumper crop of acorns causes concern for those with horses".
Countryfile.com. Immediate Media Company. 19 October 2011. Retrieved
27 January 2014.
^ a b Barringer, Sam. "Acorns Can be Deadly". West Virginia University
Extension Service. Archived from the original on 27 February 2014.
Retrieved 27 January 2014.
^ Brown, Leland R. (1979) Insects Feeding on California
Proceedings of the Symposium on Multiple-Use Management of
California's Hardwood Resources, Timothy Plum and Norman Pillsbury
^ "Nutrition Facts for
Acorn Flour". Nutritiondata.com. Retrieved
^ 1950-, Tull, Delena, (1987). A practical guide to edible &
useful plants : including recipes, harmful plants, natural dyes
& textile fibers. Austin, Tex.: Texas Monthly Press.
ISBN 9780877190226. OCLC 15015652.
^ "Two Ways to Make Cold Leached
Acorn Flour - Learn How with this
Guide". The Spruce. Retrieved 2017-12-24.
^ Janzen, Daniel H. (1971), Richard F. Johnson, Peter W. Frank and
Charles Michner, ed., "
Seed Predation by Animals", Annual Review of
Ecology and Systematics, 2: 465,
doi:10.1146/annurev.es.02.110171.002341, JSTOR 2096937
^ "Indigenous Food and Traditional Recipes". NativeTech. Retrieved
^ "Cooking With Acorns". Siouxme.com. Retrieved 2017-01-06.
^ Bainbridge, D. A. (12–14 November 1986), Use of acorns for food in
California: past, present and future, San Luis Obispo, CA.: Symposium
on Multiple-use Management of California's Hardwoods
^ Alphonso, Christina (5 November 2015). "Acres of Acorns". The
Metropolitan Museum of Art, i.e. The Met Museum. Retrieved 15 April
^ Derby, Jeanine A. (1980). "Acorns-Food for Modern Man". In Plumb,
Timothy R. Proceedings of the symposium on the ecology, management,
and utilization of California oaks, June 26–28 (PDF). USDA Forest
Service General Technical Report PSW-044. pp. 360–361.
^ Suttles, Wayne (1964), "(Review of) Ecological Determinants of
Aboriginal California Populations, by Martin A. Baumhoff", American
Anthropologist, 66 (3): 676, doi:10.1525/aa.1964.66.3.02a00360
^ Prichep, Deena (2014-11-02). "Nutritious Acorns Don't Have To Just
Be Snacks For Squirrels". The Salt : NPR. Retrieved
^ "National Trail Acorn". National Trails. Retrieved 9 October
^ "University of Connecticut". Archived from the original on 4
November 2010. Retrieved 5 November 2010.
^ Harper, Douglas. "acorn". Online
^ One or more of the preceding sentences incorporates text
from a publication now in the public domain: Chisholm, Hugh, ed.
(1911). "Acorn". Encyclopædia Britannica. 1 (11th ed.). Cambridge
University Press. pp. 152–153. This cites the New English
Dictionary, now the Oxford English Dictionary
Etymology Dictionary". www.etymonline.com. Retrieved 15
External links and further reading
Wikimedia Commons has media related to Acorns.
Acorn Soup (Miwokan recipe)
Cooking With Acorns: A Major North American Indian Food
Krautwurst, Terry (September–October 1988). "A Fall Field Guide
Nuts". Mother Earth News. Retrieved 20 October 2009.
Julia F. Parker and Beverly R. Ortiz, It Will Live Forever:
Traditional Yosemite Indian
Acorn Preparation, Heyday Books, 2nd
revised edition (1 September 1996), trade paperback, 160 pages,
ISBN 0-930588-45-2, ISBN 978-0-930588-45-8
Proceedings of the symposium on the ecology, management, and
utilization of California oaks, 26–28 June USDA Forest Service
General Technical Report PSW-044, Berkeley, California, 1980, edited
by Timothy R. Plumb, 368 pages
True, or botanical nuts
Johnstone River almond
Red bopple nut
Australian cashew nut
Borneo tallow nut
Queensland macadamia nut