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:''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 [[tree]]s and [[shrub]]s 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 [[leaf|leaves]], with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. The [[flower]]s are [[catkin]]s, produced in spring. The [[fruit]] is a [[nut (fruit)|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 oak|"live oaks"]] (oaks with [[evergreen]] leaves) are not a distinct group, instead with their members scattered among the sections below.
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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.
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.
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.
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.
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.}}
==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 (botany)|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===
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===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 [[beetle]]s, 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 [[larva]]e of [[Lepidoptera]] species.
==Species==
The genus is divided into a number of sections:
*Sect. ''Quercus'' (synonyms ''Lepidobalanus'' and ''Leucobalanus''), the [[List of Quercus species#Section Quercus|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 [[List of Quercus species#Section Mesobalanus|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 [[List of Quercus species#Section Cerris|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 [[List of Quercus species#Section Protobalanus|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 [[List of Quercus species#Section Lobatae|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.
[[List of Quercus species|'''Full list of ''Quercus'' species''']]
[[Image:Quercus stellata.jpg|thumb|A hybrid white oak, possibly ''[[Post oak|Quercus stellata]]'' × ''[[Chinkapin oak|Q. muhlenbergii]]'']]
[[Hybrid]]s 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 [http://flora.huh.harvard.edu:8080/flora/browse.do?flora_id=2&taxon_id=108828 ''Flora of China''], is often included within ''Quercus'' as a distinct subgenus.
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Index.
Index.
The following species of Castanopsis are known to be in cult.: C. ceratacantha, Rehd. & Wilson. Tree, to 50 ft.: branchlets densely villous: lvs. oblong-lanceolate to ovate-lanceolate, acuminate, obscurely toothed above the middle or entire, brownish villous-tomentose beneath, 4-6 in. long: frs. in stout spikes to 8 in. long, 1/4-1 in. across, fulvous-tomentulose, with stout prickles 1/4-1/2in. long and divided at the apex into several spreading spiny points; nuts 2-3, wholly inclosed. W. China.—C. chrysophylla, DC., see Vol. II, p. 682.—C. cuspidata, Schottky (Quercus cuspidata, Thunb. Pasania cuspidata, Oerst.). This species is already mentioned under Pasania, see p. 2479. The ovate pointed involucre is marked with 4 or 5 wavy concentric ridges of small tubercles and includes wholly the solitary nut. There are two varieties in cult.: var. latifolia, Rehd. & Wilson, with larger and broader lvs. to 4 1/2 in. long and to 2 1/2 in. broad; and var. variegata, Rehd. & Wilson, with small lvs. bordered by a broad, irregular, creamy white margin. G.C. II. 12:233.—C. Fargesii, Franch. Tree, to 100 ft.: branchlets glabrous: lvs. elliptic-oblong to lanceolate, acuminate, serrate above the middle, thinly and closely yellowish or grayish tomentulose beneath, finally nearly glabrous, 2-5 in. long: frs. in stout spikes to 6 in. long, about 3/4in. across, with stout, often reflexed fascicled spines, about 1/2in. long; nut usually solitary, wholly inclosed. Cent. China.—C. platyacantha, Rehd. & Wilson. Tree, to 80 ft.: branchlets glabrous: lvs. ovate-oblong to elliptic-oblong, acuminate, slightly toothed above the middle or entire, covered beneath, except the glabrous midrib, with a close fulvous tomentum, becoming paler the second year, 2 1/2-5 in. long: spikes short, 3-6- fruited: frs. about 1 in. across, grayish tomentulose, densely covered with short and stout fascicled prickles; nuts wholly inclosed, 1-3. W. China.—C. sclerophylla, Schottky (Q. sclerophylla, Lindl. Q. chinensis, Abel). Tree, to 60 ft.: lvs. oval to oblong-ovate or oblong, acuminate, serrate above the middle, glabrous, glaucescent beneath, 2 1/2-6 in. long: frs. in dense spikes with the peduncle to 4 in. long; involucre ovoid, with close concentric ridges of small tubercles, not wholly inclosing the solitary nut. E. and Cent.
The following species of Castanopsis are known to be in cult.: C. ceratacantha, Rehd. & Wilson. Tree, to 50 ft.: branchlets densely villous: lvs. oblong-lanceolate to ovate-lanceolate, acuminate, obscurely toothed above the middle or entire, brownish villous-tomentose beneath, 4-6 in. long: frs. in stout spikes to 8 in. long, 1/4-1 in. across, fulvous-tomentulose, with stout prickles 1/4-1/2in. long and divided at the apex into several spreading spiny points; nuts 2-3, wholly inclosed. W. China.—C. chrysophylla, DC., see Vol. II, p. 682.—C. cuspidata, Schottky (Quercus cuspidata, Thunb. Pasania cuspidata, Oerst.). This species is already mentioned under Pasania, see p. 2479. The ovate pointed involucre is marked with 4 or 5 wavy concentric ridges of small tubercles and includes wholly the solitary nut. There are two varieties in cult.: var. latifolia, Rehd. & Wilson, with larger and broader lvs. to 4 1/2 in. long and to 2 1/2 in. broad; and var. variegata, Rehd. & Wilson, with small lvs. bordered by a broad, irregular, creamy white margin. G.C. II. 12:233.—C. Fargesii, Franch. Tree, to 100 ft.: branchlets glabrous: lvs. elliptic-oblong to lanceolate, acuminate, serrate above the middle, thinly and closely yellowish or grayish tomentulose beneath, finally nearly glabrous, 2-5 in. long: frs. in stout spikes to 6 in. long, about 3/4in. across, with stout, often reflexed fascicled spines, about 1/2in. long; nut usually solitary, wholly inclosed. Cent. China.—C. platyacantha, Rehd. & Wilson. Tree, to 80 ft.: branchlets glabrous: lvs. ovate-oblong to elliptic-oblong, acuminate, slightly toothed above the middle or entire, covered beneath, except the glabrous midrib, with a close fulvous tomentum, becoming paler the second year, 2 1/2-5 in. long: spikes short, 3-6- fruited: frs. about 1 in. across, grayish tomentulose, densely covered with short and stout fascicled prickles; nuts wholly inclosed, 1-3. W. China.—C. sclerophylla, Schottky (Q. sclerophylla, Lindl. Q. chinensis, Abel). Tree, to 60 ft.: lvs. oval to oblong-ovate or oblong, acuminate, serrate above the middle, glabrous, glaucescent beneath, 2 1/2-6 in. long: frs. in dense spikes with the peduncle to 4 in. long; involucre ovoid, with close concentric ridges of small tubercles, not wholly inclosing the solitary nut. E. and Cent.
China.
China.
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==Gallery==
{{photo-sources}}<!-- remove this line if there are already 3 or more photos in the gallery -->
==Cultivation==
<gallery>
<gallery>
Image:Spanish-moss-tree.jpg|[[Southern live oak]] with [[spanish moss]]
Image:Spanish-moss-tree.jpg|[[Southern live oak]] with [[spanish moss]]
</gallery>
</gallery>
==References==
*[[Standard Cyclopedia of Horticulture]], by L. H. Bailey, MacMillan Co., 1963
<!--- xxxxx *Flora: The Gardener's Bible, by Sean Hogan. Global Book Publishing, 2003. ISBN 0881925381 -->
<!--- xxxxx *American Horticultural Society: A-Z Encyclopedia of Garden Plants, by Christopher Brickell, Judith D. Zuk. 1996. ISBN 0789419432 -->
<!--- xxxxx *Sunset National Garden Book. Sunset Books, Inc., 1997. ISBN 0376038608 -->
==External links==
==External links==
{{commonscat|Quercus}}
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