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Oak is the common name for many acorn-producing trees and shrubs that are members of the beech, or Fagaceae, family. Oak trees are classified as members of the genus Quercus, a Latin word said to be derived from a Celtic word meaning "fine tree." Worldwide there are more than 600 different species of oak. They thrive across the Northern Hemisphere in China, Japan, Europe, the British Isles, and in all of the continental United States except for Alaska. More than half of the 600 species are native to North America. Yet only about 60 varieties grow north of Mexico. In the forests of northern areas that have short summer growing seasons and long winters, such as Canada, northern Europe, and Siberia, varieties of oak are very scarce.

The oak family is a diverse group of trees and shrubs, influenced by climatic and environmental changes. Recent studies indicate that global warming contributes to oak dieback by speeding up the reproduction of beetles and fungi that attack oak trees. There are oaks that grow to heights of about 100 ft (30.5 m), while other types never grow larger than a small shrub. In warmer climates, oaks are evergreens, keep their leaves all year long, and are often used as ornamental trees in parks. In colder climates, they usually drop their leaves in autumn.

Many of these deciduous oaks have leaves that turn brilliant gold or scarlet in the autumn. In spring small, yellow green flowers appear. The male flowers hang in clusters called catkins and have profuse amounts of pollen. This oak pollen is carried by the wind to fertilize female flowers that produce acorns. Oak trees grow very slowly. In 80 years, it's estimated that one will grow to no more than 2 ft (0.6 m) in diameter. Oaks do not even produce acorns for their first 20 years, but they live a very long time. Average life expectancy for most oaks is between 200 and 400 years, and there are oak trees over 800 years old that are still alive.

Oaks are divided into two basic categories: white and red. The leaves of most of these are characteristically lobed, and depending upon the variety, can have anywhere from five to 11 lobes. Historically, the oak has been considered sacred by many civilizations. Abraham's Oak, the Oak of Mamre, is thought to be on the spot where the bible states Abraham pitched his tent. Legend states that anyone defacing this tree will lose their firstborn son. Both the ancient Greeks and Romans revered the oak, but its longest association has been with the British Isles. The Druids considered it to have both medicinal and mystical significance. For centuries, an oak sprig was inscribed on English coins. Legend states that King Arthur's round table was made from one gigantic slice of a very ancient oak tree. Oak has been used as a medicine since the ancient Greek and Roman times. The famous Roman doctor Galen first used oak leaves to heal wounds .

The American white oak, Quercus alba, and the English oak, Quercus robur, have bark with similar healing qualities. Oak bark contains saponins, tannins, calcium oxalate, starch, glycosides, oak-red, resin, pectin, levulin, and quercitol.

General use

Oak wood as timber is prized for its strength, elasticity, and durability. It is ideal for making furniture, barrels, railroad ties, and in the past, ships. Oak acorns are a source of food for wildlife and have been used as fodder for farm animals in the past. A flour made from ground acorns was also a part of the diet of Native Americans. The tannin in oak bark is used in leather preparation. Cork is made from the bark of some species that grow only in Spain and Portugal.

Recent advances in molecular genetics have shown that DNA from samples of oak can be isolated and analyzed. This type of analysis has a variety of potential applications in archaeology and forensic investigations.

Oak used to make wine barrels has been found to increase the antioxidant activity of wines aged in the barrels as well as adding a distinctive aroma to the wine. The increase in antioxidant activity can be measured by a new technique known as electron paramagnetic resonance, or EPR.

Oak bark is used in medicine as a bowel astringent to treat diarrhea and as an anti-inflammatory gargle for soothing sore throats. It can be used topically for such skin inflammations as dermatitis , as an enema for hemorrhoids , or as a douche for vaginal infections and leukorrhea. A study in 1980 showed some evidence that oak bark may prevent kidney stone formation and act as a diuretic. A 1990 Russian study demonstrated that oak bark had antibacterial activity against Staphylococcus. One study in 1994 showed that oak bark could reduce serum cholesterol levels in animals.


One teaspoonful of pulverized oak bark powder can be added to 1 cup of water, boiled, and then simmered at a reduced heat for 15 minutes to make an oak bark tea. This tea can be taken internally as an intestinal astringent up to three times per day. Oak bark is also available in both an extract and a tincture. For rinses, compresses, and gargles, 20 g of pulverized bark should be dissolved in 1 qt (1 L) of water, and prepared in the same manner as the tea. Oak bark is also available as snuff, tablets, and capsules.


Oak bark should not be used externally over large areas of skin damage or used as a full bath. Oak bark for gargles, enemas, or douches should not be used for more than two weeks before consulting a doctor. A doctor should also be consulted for any episode of diarrhea that lasts longer than three days despite treatment with oak bark.

Side effects

No side effects have been reported when oak preparations are used at recommended dosage levels. Patients occasionally experience mild stomach upset or constipation if the dosage is exceeded.


Oak bark preparations are believed to inhibit or reduce the absorption of such alkaline drugs as antacids. In addition, oak bark has been found to reduce the effectiveness of codeine and atropine.



Grieve, M., and C. F. Leyel. A Modern Herbal: The Medical, Culinary, Cosmetic and Economic Properties, Cultivation and Folklore of Herbs, Grasses, Fungi, Shrubs and Trees With All of Their Modern Scientific Uses. Barnes and Noble Publishing, 1992.

Hoffman, David, and Linda Quayle. The Complete Illustrated Herbal: A Safe and Practical Guide to Making and Using Herbal Remedies. Barnes and Noble Publishing, 1999.


Deguilloux, M. F., M. H. Pemonge, and R. J. Petit. "Novel Perspectives in Wood Certification and Forensics: Dry Wood as a Source of DNA." Proceedings of the Royal Society of London, Series B, Biological Sciences 269 (May 22, 2002): 1039-1046.

Diaz-Playa, E. M., J. R. Reyero, F. Pardo et al. "Influence of Oak Wood on the Aromatic Composition and Quality of Wines with Different Tannin Contents." Journal of Agriculture and Food Chemistry 50 (April 24, 2002): 2622-2626.

Kamata, N., N. Kamata, K. Esaki, et al. "Potential Impact of Global Warming on Deciduous Oak Dieback Caused by Ambrosia Fungus Raffaelea sp. Carried by Ambrosia Beetle Platypus quercivorus (Coleoptera: Platypodidae) in Japan." Bulletin of Entomological Research 92 (April 2002): 119-126.

Troup, G. J., and C. R. Hunter. "EPR, Free Radicals, Wine, and the Industry: Some Achievements." Annual of the New York Academy of Science (May 2002): 345-347.


Herbal Advisor. http//www.AllHerb.com

OnHealthHerbal Index. "Oak Bark." http//www.OnHealth.com

Joan Schonbeck

Rebecca J. Frey, PhD

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OAK (Heb. אַלּוֹן), the main trees of Israel's natural groves and forests. The three species which grow there have in common their strong and hard wood and all attain a great height and reach a very old age. The Hebrew name, allon, means strong (Amos 2:9). Extensive oak forests still exist in Bashan, and these, together with the cedars of Lebanon, symbolized pride and loftiness (Isa. 2:13; Zech. 11:2). The people of Tyre made the oars for their ships from the oaks of Bashan (Ezek. 27:6). Some oaks served as sites for idol worship (Hos. 4:13), and burial took place under them (Gen. 35:8). The oak is long-lived and when it grows old or is cut down it has the ability to renew itself, putting out new shoots from the stump or roots that in time develop into a strong tree. In his prophecy describing the fate of the Jewish people, for whom it was decreed that they should suffer great losses, the prophet Isaiah uses the image of the old oak (together with an elah, *terebinth) standing near the gate Shallekhet in Jerusalem that frequently had its branches and trunk cut down, only its stump remaining; yet no sooner was it felled, than the stump put forth "holy seed," sprouting new shoots (Isa. 6:13). Possibly Isaiah 11:1: "And there shall come forth a shoot out of the stock of Jesse, and a twig shall grow forth out of his roots" is a continuation of this chapter.

Evidence of this phenomenon can be seen in many oaks in Israel today. The most famous, and apparently the oldest of them, is "the oak of Abraham" in Hebron. This oak, or one of its ancestors, is mentioned in the Apocrypha – Jubilees and Tobit – as the tree under which Abraham received the kings. Josephus (Ant., 1:186; cf. Wars, 4:533) also speaks of it. *Jerome notes that Titus sold 10,000 Judean captives under this tree. Since the third century many Jewish and Christian pilgrims have mentioned that this tree is considered sacred. It is an evergreen of the species Quercus calliprinos, which constitutes most of the groves in the hills of Judea and Galilee. Most of them look like shrubs as a result of continuous felling and of being gnawed by goats. Some giant trees still survive (as for example at Aqua Bella, now called Ein Ḥemed). The other two species of oak growing in Israel are deciduous. On the hills of Lower Galilee (in the vicinity of Tivon and Allonim) there exist groves of the Tabor oak (Quercus ithaburensis). This tree is also to be seen in the Ḥurshat Tal in the Ḥuleh valley where there are about 200 giant trees (50 ft. high with trunks of 16 ft. or more in circumference). The third species is the Quercus infectoria (Quercus boissier), called in Hebrew by the corresponding name tola oak because of the *crimson worm (tola) which lives off its branches (as it does off the Tabor oak). This tree, which has a tall straight trunk, is called in the Mishnah milah or milast (Mid. 3:7).


Loew, Flora, 1 (1928), 621–34; Feliks, in: Sinai, 38 (1956/57), 85–102; idem, Olam ha-Ẓome'aḥ ha-Mikra'i (19682), 107–9; H.N. and A.L. Moldenke, Plants of the Bible (1952), index. add. bibliography: Feliks, Ha-Ẓome'aḥ, 27, 99.

[Jehuda Feliks]

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oak allusion is often made to the hardness and durability of the oak, and to the traditional use of oak timber for ships. In traditional rhymes, it may be linked and compared with other trees, as the ash and the thorn.

The Oaks is an annual flat horse race for three-year-old fillies run on Epsom Downs, over the same course as the Derby. It was first run in 1779, and is so called from the estate of the 12th Earl of Derby, owner of the first winner.
beware of an oak, it draws the stroke; avoid an ash, it counts the flash; creep under the thorn, it can save you from harm proverbial saying, late 19th century, recording traditional beliefs on where to shelter from lightning during a thunderstorm.
Oak-apple Day the anniversary of Charles II's restoration (29 May), when oak-apples or oak-leaves used to be worn in memory of his hiding in an oak after the battle of Worcester.
sport the (or one's) oak (in certain universities) shut the outer door of one's room as a sign that one does not wish to be disturbed (such doors were formerly made of oak).
when the oak is before the ash, then you will only get a splash; when the ash is before the oak, then you may expect a soak proverbial saying, mid 19th century; a traditional way of predicting whether the summer will be wet or dry on the basis of whether the oak or the ash is first to come into leaf in the spring.

See also great oaks from little acorns grow, heart of oak, little strokes fell great oaks, a reed before the wind lives on, while mighty oaks do fall.

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oak / ōk/ • n. (also oak tree) a tree (genus Quercus) of the beech family that bears acorns as fruit, and typically has lobed deciduous leaves. Oaks are common in many north temperate forests and are an important source of hard and durable wood used chiefly in construction, furniture, and (formerly) shipbuilding. Its many species include the Eastern white oak (Q. alba) and Eastern black oak (Q. velutina). DERIVATIVES: oak·en / ˈōkən/ adj. oak·y adj.

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oakawoke, bespoke, bloke, broke, choke, cloak, Coke, convoke, croak, evoke, folk, invoke, joke, Koch, moke, oak, okey-doke, poke, provoke, revoke, roque, smoke, soak, soke, spoke, stoke, stony-broke (US stone-broke), stroke, toke, toque, woke, yoke, yolk •Holyoake • artichoke • gentlefolk •menfolk • kinsfolk • womenfolk •townsfolk • fisherfolk • holmoak •woodsmoke • cowpoke • slowpoke •backstroke • breaststroke • keystroke •heatstroke • sidestroke • downstroke •sunstroke • upstroke • masterstroke •counterstroke • equivoque

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oak Common name of c.600 species of the genus Quercus, which are found in temperate areas of the Northern Hemisphere and at high elevations in the tropics. Most species are hardwood trees that grow 18–30m (60–100ft) tall. Leaves are simple, often lobed, and sometimes serrated. The flowers are greenish and inconspicuous; male flowers hang in catkins. The fruit is an acorn, surrounded by a cup.

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2.. (African oak) See OCHNACEAE.

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oak OE. āc (pl. ǣċ) = MLG. ēk (Du. eik), OHG. eih (G. eiche), ON. eik :- Gmc. *aiks; ulterior connections unkn.