"Away from the clutter and tangle of forest, they grow massive, their trunks thick,
their branches spreading with a vast graciousness above the golden grasses. They
are old, quiet trees, laden with tough, curled leaves and clusters of honey-brown
nuts, and it is to them we went to learn about harvesting acorns."
-Nell, Into the Forest

Family: Fagaceae (Beech)
Other names: None; oak has a long established history in our culture as the archetypal tree and thus has always been known simply as oak.
Name meaning: The words oak and acorn both come from the Old English ac, meaning oak. Quercus is Latin for oak.
Origin: There are species of oak on every continent except Antarctica. Most of the oaks you're likely to see in North America are native, though there are many popular non-native species planted ornamentally, particularly as street trees.
Range: Found on every continent except Antartica. In North America there are oaks everywhere below the tree line.
Habitat: Varies by species; oak is a common staple in forests of all types. Some species are popular as street trees.
Life cycle: Perennial
Description: A large, deciduous, well-known tree, with alternate leaves that are usually pinnately lobed, bearing drooping clusters of tiny yellow-brown flowers in the spring and small capped nuts (acorns) in the fall. There are many species; often divided into red oaks and white oaks. Red oaks have leaves with lobes which are divided at the tip with sharp points on either side, reddish wood, and usually round, flat-topped acorns; whereas white oaks have rounded lobes, white wood, and long, narrow acorns with round tops. Many species grow to 80 feet or more, though some, such as scrub oak, are shrub-size.

Uses

Edible: The acorns of oak trees, much to the surprise of many people, are edible, and in fact have been a major source of food for many people through history and prehistory, all over the world, including medieval peasants in times of famine, the Native Americans of California, and many others. Unfortunately, acorns contain the bitter and sometimes toxic tannic acid, which makes most of them inedible raw, although some white oaks contain so little that they are palatable raw. Luckily, it is quite easy to remove the tannic acid through a number of methods of leaching with water, and after it is removed, acorns are perfectly edible and quite nutritious. One method is to shell the acorns (removing any worm-eaten parts), dry the nutmeats, grind them to a rough flour with a mortar and pestle or a mechanical grinder (I find that a coffee grinder works well), and boil them, changing the water each time it turns dark. Use already-boiling water every time you change it or the bitterness will be locked in. Another method is to place the whole, cracked, or ground nutmeats in a stream or brook for a long time, leaving them in some kind of container the water can get through such as a mesh bag or a coffee can with holes in the bottom, and let the cold water leach out the tannins. You can also pour cold tap water through the container again and again if there is no stream available. Some Indian tribes also buried the acorns underground for a number of months, which eventually would leach the tannins out. Once you have leached them, there are many ways to prepare acorns. If they were leached whole or cracked they can be roasted in an oven or over a fire, and sometimes are coated with sugar first to make a sort of acorn candy, or you may grind them after the leaching. If they have been ground, they can be used as flour to make all sorts of breads, cakes pastries, etc., or to mix with hot water to make mush, or to add to soups for thickening, and is one of the best flours you can get from the wild. If you plan to store the unprocessed nuts for the future, don’t store them in their shells, or you will be sorely dissapointed when you crack them open later and find they’ve all been eaten by worms. If you shell them within a few days of collecting them, and remove all worms and worm-eaten parts, they can last for months (kept away from squirrels of course). (This is only basic outline; for more information on processing acorns, check Cooking with Acorns, or the book It Will Live Forever.)

Medicinal: The water left over from the acorn leaching process, and a tea made from the nut shells, are high in tannic acid, which makes an excellent astringent. This is used externally as a wash for inflammations, sores, hemorrhoids, and many other skin maladies, including poison ivy rash, as well as a mouthwash for canker sores and other similar mouth problems. Internally, it is used for dysentery and chronic diarrhea. The boiled inner bark can be used the same way. The Pomo Indians used molded acorn meal as an antibiotic. Experiments show that tannic acid may be antiseptic, antiviral, and anti-cancer, but may also be a carcinogenic.

Utilitarian: The hard wood of oak trees makes it excellent for tool handles and other uses which require hard wood, and it is often used to make furniture. Oak barrels are the prefered vessels for aging wine. Tannic acid found in the acorns and inner bark is a natural preservative, and can be used to tan animal hides. It does not work as well as brain tanning, but is still an excellent natural method. Tannic acid is used as a natural dye, ranging from pale yellow to brown to black, depending on the concentration.

Magical: Oak is a universal symbol of strength, and is associated with protection and the home, and also fertility and prosperity. Oaks were particularly sacred to the Celts in ancient times. Their priests were called Druids, which is believed to be derived from the words for oak and wisdom. Magic wands are made from the wood, and burning the leaves or wood is said to purify the area.

Warning: Tannic acid can be toxic in large amounts; make sure you leach your acorns well and be very careful with the internal medical uses.

Where to find oak

Oak is common in many types of forests, and is planted along streets. The acorns can be gathered in late summer or early autumn as soon as they fall from the trees. Acorns are plentiful, but remember that they are an important food source for many animals, so don't take too many, and make sure to check local laws before gathering from public lands. Also be aware that acorns from street trees might contain pollutants.

Links

Wikipedia: Oak
Cooking with Acorns
Harvesting the Wild: Acorns
How to Use Acorns for Bread and Food
Botantical.com: Oak
Plants for a Future: Quercus species
King's American Dispensatory: Quercus alba
Herbs2000.com: Oak
An Illustrated Herbal: Oak Tree
Herbs and Oils: MNO (scroll down to oak)
Alchemy Works: White Oak Bark
Hardwoods (scroll down to Quercus)
USDA Plant Profile: Quercus