Acorn
Categories: 1911 Britannica | Nuts and seeds
This article is about the seed; for other meanings of the word, see acorn (disambiguation).
The acorn is the fruit of the oak tree.
Contents |
Nutrition
Many creatures, including humans, eat acorns. In some human cultures, acorns once constituted a dietary staple. Other creatures that make acorns an important part of their diet include birds such as jays, band-tailed pigeons, wood ducks and several species of woodpeckers. Small mammals that prey on acorns include deer mice, ground squirrels, grey squirrels, woodrats and pocket gophers. Large mammals such as bear and deer also consume large amounts of acorns. (Janzen) Acorns may constitute up to 25% of deer diets in the autumn. The larvae of certain moths and weevils also live in young acorns, consuming the kernels as they develop. (Brown) Acorns are thus one of the most important wildlife foods in North America and in parts of Europe. In some of the large oak forests that remain in Spain, Portugal and southern France, pigs are still turned loose in oak groves in the fall, to fill and fatten themselves on acorns.
Acorns are attractive to humans and other animals because they are large and thus efficiently consumed or cached. Acorns are also packed with nutrients. Percentages vary from species to species, but all acorns contain large percentages of protein, carbohydrates and fats, as well as the minerals calcium, phosphorus, potassium and 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 utilize the nutritional bounty that acorns offer in oak territory. Animals may preferentially select acorns that contain fewer tannins. Creatures 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 the tannins out. Other animals buffer their acorn diet with other foods. And many insects, birds and mammals metabolize tannins with fewer ill-effects than humans. Humans, being cultural creatures, devised acorn-leaching methods that involved tools, and that could be passed on to their children.
However, some species of acorns contain large amounts of tannins, making them bitter, astringent, and potentially irritating if eaten raw. This is particularly true of the dark-colored acorns of red oaks. The light-colored acorns of white oaks, being much lower in tannins, are nutty in flavor which is enhanced if the acorns are given a light roast before grinding. Tannins can be removed by boiling chopped acorns in several changes of water (until water no longer turns brown). Being rich in fat, acorn flour can spoil or mold easily and must be carefully stored. Acorns are also sometimes prepared as a massage oil.
Acorns are also a favorite food for many animals, including deer, grouse, and squirrels. Squirrels have been observed eating white oak acorns preferentially and burying the much more bitter red oak acorns for later use, since ground moisture causes the tannins to leach out over time. However, acorns are toxic to other animals, such as horses.
Cultural aspects
Acorns take about 6 or 24 months (depending on the species) to mature and appear only on adult trees, and thus are often a symbol of patience and the fruition of long, hard labor. For example, an English proverb states that Great oaks from little acorns grow, urging the listener to wait for maturation of a project or idea. A German folktale has a farmer outwit Satan, to whom he has promised his soul, by asking for a reprieve until his first crop is harvested; he plants acorns and has many years to enjoy first. In Britain, one old tradition has it that if a woman carries an acorn on her person it will delay the ageing process and keep her forever young. In the United States, botanists joke that even the greatest oak was once a little nut.
The Norse legend that Thor sheltered from a thunderstorm under an oak tree has led to the belief that having an acorn on a windowsill will prevent a house from being struck by lightning, hence the popularity of window blind pulls decorated as acorns.
Young lovers may place two acorns, representing themselves and the object of their affection, in a bowl of water in order to predict whether they have a future together: if the acorns drift towards each other they are certain to marry. (They will, if placed closer to each other than to the edge of the bowl.)
In the 1600s, 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.
In ancient Japan (Jomon period) acorn was important food. They soaked harvested and peeled acorn in natural or artificial ponds for several days to remove tannins. Then they processed it to acorn cakes.
Acorns were a traditional food of many indigenous peoples of North America, but served an especially important role in Native California, where the ranges of several species of oaks overlap, increasing the reliability of the resource.
Acorn Dispersal Agents
The proverbial acorn does not fall far from the tree, and neither does the natural one. Because of this, an oak depends on certain seed dispersal agents to move its acorns beyond the canopy of the mother tree and into an environment in which they can germinate and find access to adequate water, sunlight and soil nutrients, ideally a minimum of 100 feet from the parent tree. Most acorn predators devour unripe acorns on the tree or ripe acorns from the ground, with no reproductive benefit to the oak. However, a few acorn predators also serve as seed dispersal agents. Jays and 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. Although 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 or abandon territory without consuming all of its stores. A small number of acorns manage to germinate and survive, and pass on their parents' genes.
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 them.
Germination
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 root.
Processing for Human Consumption
Native North Americans processed whole acorns most simply by burying them in mud or immersing them in a stream until the tannins leached out. But as intensification of this resource increased to supply acorn mush or acorn bread for one or two meals a day, the processing became more elaborate, and removal of tannins took place by repeated leaching in sand basins, after the acorns had been shelled, stripped of their black skins and pulverized into meal. California Indian women developed a suite of baskets for processing acorns. These included conical collection baskets worn over the back, bottomless hopper mortar baskets that sat on flat rocks while women pounded shelled acorns into meal with a mortar, sifting baskets and scoops to lift hot stones from a fire into large cooking baskets full of water and acorn meal. The hot stones brought the water to a boil and cooked the acorn mush, which was served in special acorn mush bowls. Acorn meal might also be shaped into cakes and roasted as bread on hearthstones.
Acorns, unlike many other plant foods, do not need to be eaten or processed immediately, but may be stored for long time periods. 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, Indian women took acorns back to their villages and cached them in hollow trees or structures on poles, to keep acorns safe from mice and squirrels. These acorns could be used as needed. Storage of acorns permitted Native American women to process acorns when convenient, particularly during winter months when other resources were scarce. Women's caloric contributions to the village increased when they stored acorns for later processing and focused on gathering or processing other resources available in the autumn.
Women shelled and pulverized those acorns that germinate in the fall before those that germinate in spring. Because of their high fat content, stored acorns can become rancid. Molds may also grow on them. Nevertheless, a rancid, moldy acorn looks tasty when no other food is available.
Native American Management of Acorn Resources
Native North Americans took an active and sophisticated role in management of acorn resources through the use of fire, which increased the production of acorns and made them easier to collect. Purposefully setting light ground fires killed the larvae of acorn moths and acorn weevils that have the potential to infest and consume more than 95% of an oak's acorns, by burning them during their dormancy period in the soil. Fires 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 faster and 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 those conifers which are less tolerant of fire, thus keeping landscapes in a subclimax state in which oaks dominated. Since oaks produce more acorns when they are not in close competition with other oaks for sunlight, water and soil nutrients, eliminating young oaks more vulnerable to fire than old oaks created open oak savannahs with trees ideally spaced to maximize acorn production. Finally, frequent fires prevented accumulation of flammable debris, which reduced the risk of destructive canopy fires that destroyed oak trees. After a century during which North American landscapes have not been managed by indigenous peoples, disastrous fires have ravaged crowded, fuel-laden forests. Land managers have realized that they can learn much from indigenous resource management techniques, such as controlled burning, widely practiced by Native Americans to enhance such resources as acorns.
gothic language|Gothic]] akran, German Eicher, etc., and 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". By degrees, popular etymology connected the word both with "corn" and "oak-horn", and the spelling changed accordingly.
By analogy with the shape, in nautical language, the word acorn also refers to a piece of wood keeping the vane on the mast-head.
Bibliography
Baumhoff, Martin A. (1963) Ecological Determinants of Aboriginal California Populations. University of California Publications in American Archaeology and Etnology 49(2)155-235.
Brown, Leland R. (1979) Insects Feeding on California Oak Treesin Proceedings of the Symposium on Multiple-Use Management of California's Hardwood Resources, Timothy Plum and Norman Pillsbury (eds.). Gen. Tech. Rep. PSW-44, USDA, Forest Service, Pac. S.W. Forest and Range Experiment Station, Berkeley, California, pp. 184-194.
Janzen, Daniel H. (1971) Seed Predation by Animals in Annual Review of Ecology and Systematics. Richard F. Johnson, Peter W. Frank and Charles Michner (eds.).
External links
- Nupa Acorn Soup (Miwokan recipe)
- Cooking With Acorns: A Major North American Indian Food
- nutrition facts for acorn flour
- How to whistle an acorn
This article incorporates text from the 1911 Encyclopædia Britannica, which is in the public domain.da:Agern de:Eichel (Frucht) es:Bellota ja:ドングリ pl:Żołądź (botanika) sv:ekollon fr:gland (fruit) zh:栓皮櫟