- This article is about oaks (Quercus). For other uses of "Oak" or "Oak tree", see Oak (disambiguation)
The term oak can be used as part of the common name of any of several hundred species of trees and shrubs in the genus Quercus, and some related genera, notably Cyclobalanopsis and Lithocarpus. The genus is native to the northern hemisphere, and includes deciduous and evergreen species extending from cold latitudes to tropical Asia and the Americas.
Oaks have spirally arranged leaves, with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. The flowers are catkins, produced in spring. The fruit is a nut called an acorn, borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6-18 months to mature, depending on species. The "live oaks" (oaks with evergreen leaves) are not a distinct group, instead with their members scattered among the sections below.
Read about Oak in the Standard Cyclopedia of Horticulture
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Quercus (ancient Latin name). Fagaceae. Oak. Ornamental trees, rarely shrubs, grown chiefly for their handsome foliage and interesting habit; many species are important timber trees. See Oak. Deciduous or evergreen trees, rarely shrubby: winter buds with usually many imbricate scales: lvs. alternate, short-petioled, with deciduous stipules, pen- ninerved, serrate, lobed or pinnatifid, rarely entire: fls. monoecious; the staminate in slender, pendulous catkins with 4-7-parted calyx and 4-12, usually 6, stamens; pistillate in 1- to many-fld. spikes in the axils of the young lvs., each fl. consisting of an incompletely 3-, or rarely 4-5-celled ovary, surrounded by imbricate bracts; style short or elongated, dilated above and stigmatic on the inner face: fr. a 1-seeded subglobose to oblong nut, surrounded at the base or sometimes almost inclosed by a cup-like involucre.—More than 200 species are known, distributed through the colder and temperate regions of the northern hemisphere and in the mountains of the tropics. The numerous species are usually divided into 3 subgenera. The species of the subgenus Cyclobalanopsis which has the scales of the cup connate into concentric rings are all Asiatic. The American species belong to Lepidobalanus (balanos is Greek for acorn) and to Erythrobalanus. In the former, comprising the white oak tribe, the acorns mature the first year (Fig. 3304). In the latter, comprising the black oaks, the acorns mature the second year (Fig. 3305). Besides the 200 species, about 40 hybrids have been recorded. Pasania, often included under Quercus, is now usually considered a distinct genus, which see. The latest monograph of the whole genus is by A. DeCandolle in "Prodromus," vol. 16, 2, pp. 1-108 (1864-1868). Important illustrated works on American oaks are A. Michaux, "Histoire des Chenes de l'Amerique" (1801), with 36 plates; Kellogg and Greene. "Illustrations of West American Oaks" (1889), with 37 plates; Sargent, "Silva of North America," vol. 8 (1895), with 82 plates, and Liebmann, "Chenes de l'Amerique Tropicale" (1869), with 47 plates. Most of the European and west Asian oaks are figured in Kotschy "Eichen Europas und des Orients" (1862), with 40 colored plates. For comparative illustrations of lvs. see M.D. 1900, p. 32; R.B. 27, p. 61; G.W. 7, pp. 570, 571, 573; for those of frs. see M.D. 1900, p. 40; R.B. 27, p. 109. The oaks are mostly trees, often tall with massive trunk and stout spreading limbs, with medium-sized, short-petioled leaves, usually more or less lobed, dentate or serrate, rarely entire, with inconspicuous flowers, the staminate ones in slender pendulous catkins and with fruits or "acorns" consisting of a globular to oblong nut inclosed at the base only, rarely wholly or nearly wholly, by a cup-like involucre. The oaks comprise some of the most important forest trees of the northern hemisphere. The wood of most species is strong, tough, hard and durable, and highly valued for many purposes, especially ship-building, construction, for furniture, and in the manufacture of wagons, tools and many other articles. The bark of some species, in America that of Q. velutina and Q. Prinus, is used for tanning leather. Cork is obtained from the bark of Q. Suber and Q. occidentalis in southern Europe. The bark of a few species has also been employed in medicine. The acorns of several species are edible, in America especially those of Q. Prinus, Q. Emoryi and Q. lobata; in Europe those of Q. Ilex var. Ballota and Q. Egilops; in Japan those of Q. glauca; in many European countries the acorns of all species are an important food for hogs. In eastern Asia a silkworm feeds on the leaves of different species. A parasitic insect living on Q. coccifera in southern Europe and northern Africa yields a scarlet dye. Galls caused by the puncture of certain insects are used for tanning and dyeing and are now chiefly obtained from Q. Ilex var. infectoria in western Asia. Some of the above-mentioned species are described only in the supplementary list, page 2890. The deciduous species are mostly hardy North, while of the evergreen ones none seems to be hardy farther north than Washington, D.C.; some half-evergreen oaks, as Q. Pseudoturneri and Q. macedonica, will probably prove hardy in the vicinity of New York. Most of the oaks are stately trees of noble and majestic habit with stout, wide-spreading branches; some, as Q. alba, Q. Garryana, Q. vir- giniana, and Q. chrysolepis, often cover a space more than 100 feet in diameter; others, as Q. macrocarpa, Q. montana and Q. velutina, have a more oval, round- topped head, while Q. palustris and Q. imbricaria form symmetrical broad pyramids. A very few hardy species are shrubs, generally called scrub oaks, as Q. prinoides and Q. ilicifolia. Oaks rank among our most valuable park and avenue trees, and are as beautiful when grown as single trees as they are when grouped together and forming groves and woods. As avenue trees, Q. palustris, Q. rubra, Q. coccinea. Q. imbricaria and Q. Phellos are among the best, the last- named when medium-sized trees are desired; in the southern states, Q. laurifolia, Q. nigra, and the evergreen Q. virginiana are preferred. The shrubby species, like Q. prinoides and Q. ilicifolia, may be used for covering rocky hillsides and dry ridges. Oak leaves are always beautiful. They have many shades of green; especially attractive are some with leaves of contrasting colors, the under side being silvery white, the upper one dark green, as in Q. Muhlenbergii, Q. macrocarpa, Q. Prinus, and some foreign evergreen species. In many oaks the leaves show a handsome pink or crimson color when unfolding, and some species assume brilliant autumnal tints. Especially beautiful in autumn are Q. coccinea and Q. palustris, with the foliage turning brilliant scarlet; Q. rubra, Q. imbricaria, and Q. Prinus, which turn bright or dark red; Q. alba, violet or vinous purple; Q. lyrata, scarlet or orange; Q. Phellos, pale yellow; Q. montana, orange or orange- brown; Q. falcata and Q. ilicifolia, orange-brown or yellow; Q. stellata and Q. nigra, brown or dull orange. Some of the foreign species, like Q. sessiliflora and also Q. Robur, Q. Cerris, Q. lanuginosa, Q. glandulifera, and others, retain the green color until late in fall. Besides our native evergreen species, the Japanese Q. acuta, Q. myrsinaefolia, and Q. glauca are among the best evergreen oaks for cultivation in the South; the European Q. Ilex and Q. Suber are also handsome evergreen trees. Generally the oaks grow best in a moderately moist rich soil, including heavy clay; some, as Q. bicolor, Q. nigra, Q. alba, Q. Phellos, Q. falcata, and Q. virginiana, prefer moister situations and grow naturally in low and often even in swampy ground; while others, especially the red oaks, like Q. rubra, Q. coccinea, Q. imbricaria, Q. marilandica, Q. montana. and Q. stellata, grow well in drier, rocky or sandy soil, and the scrub oaks on dry and barren soil. The black and red oaks especially the pin oak, are usually easily transplanted and large trees are moved successfully, while the white oaks are more particular and only younger nursery- grown trees can be safely transplanted. Oaks are propagated usually by seeds sown immediately after gathering in fall; this is especially necessary with Q. alba. Q. virginiana, and some other white oaks which sprout as soon as they are ripe; but only the root is produced in fall, while the stem does not appear until the following spring. The seeds of red and black oaks, and also of Q. Robur, if not sown at once should be stratified and sown early in spring. Acorns should be packed in earth, moss, or sawdust when shipped for a great distance. Varieties are usually grafted on potted stock in the greenhouse in early spring or sometimes in August. As a stock Q. Robur is preferred, but Q. rubra, Q. velutina, and Q. montana are also employed. It is probably safer to graft varieties of white and of red oak each on stock of the same group. The evergreen species are sometimes increased by layers and also by cuttings. The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text. |
Cultivation
Oak catkins are made up of small, yellowish-green flowers. Acorns appear after the female flowers are fertilized in spring. They are typically brown, tan, yellow, light green, deep green or grayish green. Oaks grow slowly and usually do not bear acorns until they are about 20 years old. Acorns require stratification to stimulate sprouting. Most white oaks need immediate stratification; species such as the Chestnut oak (Quercus montana) will sprout a root upon falling and must have a suitable substrate for immediate rooting. Many red oak acorns can be stratified for up to two years before sprouting. The life span of oaks typically ranges from 200 to 600 years, with a few species reaching 1,000 years.
Propagation
Pests and diseases
Sudden Oak Death (Phytophthora ramorum) is a water mould that can kill oaks within just a few weeks. Oak Wilt, caused by the fungus Ceratocystis fagacearum (a fungus closely related to Dutch Elm Disease), is also a lethal disease of some oaks, particularly the red oaks (the white oaks can be infected but generally live longer). Other dangers include wood-boring beetles, as well as root rot in older trees which may not be apparent on the outside, often only being discovered when the trees come down in a strong gale. Oaks are used as food plants by the larvae of Lepidoptera species.
Species
The genus is divided into a number of sections:
- Sect. Quercus (synonyms Lepidobalanus and Leucobalanus), the oaks of Europe, Asia and North America. Styles short; acorns mature in 6 months, sweet or slightly bitter, inside of acorn shell hairless. Leaves mostly lack a bristle on lobe tips, which are usually rounded.
- Sect. Mesobalanus, the Hungarian oak and its relatives of Europe and Asia. Styles long; acorns mature in 6 months, bitter, inside of acorn shell hairless (closely related to sect. Quercus and sometimes included in it).
- Sect. Cerris, the Turkey oak and its relatives of Europe and Asia. Styles long; acorns mature in 18 months, very bitter, inside of acorn shell hairless. Leaves typically have sharp lobe tips, with bristles at the lobe tip.
- Sect. Protobalanus, the Canyon live oak and its relatives, in southwest United States and northwest Mexico. Styles short, acorns mature in 18 months, very bitter, inside of acorn shell woolly. Leaves typically have sharp lobe tips, with bristles at the lobe tip.
- Sect. Lobatae (synonym Erythrobalanus), the red oaks of North America, Central America and northern South America. Styles long, acorns mature in 18 months, very bitter, inside of acorn shell woolly. Leaves typically have sharp lobe tips, with spiny bristles at the lobe tip.
Hybrids are common in oaks but usually only between species within the same section; no verified inter-section hybrids are known, except between species of sections Quercus and Mesobalanus, where several occur.
The genus Cyclobalanopsis, here treated as a distinct genus following the Flora of China, is often included within Quercus as a distinct subgenus.
Read about Oak in the Standard Cyclopedia of Horticulture
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{{{1}}} The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text. |
Gallery
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A Pedunculate oak in Denmark
An oak tree at night
Bark of Quercus robur
References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Oak. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Oak QR Code (Size 50, 100, 200, 500)