Quercus robur
Quercus robur, the pedunculate ' oak', is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native to most of Europe and western Asia, and is widely cultivated in other temperate regions. It grows on soils of near neutral acidity in the lowlands and is notable for its value to natural ecosystems, supporting a very wide diversity of herbivorous insects and other pests, predators and pathogens.
Description
Pedunculate oak is a deciduous tree up to tall, with a single stout trunk that can be as much as in girth or even 14 m in pollarded specimens. Older trees tend to be pollarded, with boles about 3 m long. They often live longer and become more stout than unpollarded trees.The crown is spreading and unevenly domed, and trees often have massive lower branches. The bark is greyish-brown and closely grooved, with vertical plates. There are often large burrs on the trunk, which typically produce many small shoots. Oaks do not produce suckers but do recover well from pruning or lightning damage. The twigs are hairless and the buds are rounded, brownish and pointed.
The leaves are arranged alternately along the twigs and are broadly oblong or ovate, 10–12 cm long by 7–8 cm wide, with a short petiole. They have a cordate base and 3–6 rounded lobes, divided no further than halfway to the midrib. The leaves are usually glabrous or have just a few simple hairs on the lower surface. They are dark green above, paler below, and are often covered in small disks of spangle gall by autumn.
Flowering takes place in spring and the flowers are wind-pollinated. The male flowers occur in narrow catkins some 2-4 cm long and arranged in small bunches. The female flowers are small, brown with dark red stigmas, about 2 mm in diameter and are found at the tips of new shoots on peduncles 2–5 cm long.
The fruits are borne in clusters of 2–3 on a long peduncle 4–8 cm long. Each acorn is 1.5–4 cm long, ovoid with a pointed tip, starting whitish-green and becoming brown, then black. As with all oaks, the acorns are carried in a distinctive shallow cup which can be useful in identifying the species. It is an "alternate bearing" species, with large crops produced every other year.
Chemistry
/roburin E, castalagin/vescalagin, gallic acid, monogalloyl glucose and valoneic acid dilactone, monogalloyl glucose, digalloyl glucose, trigalloyl glucose, rhamnose, quercitrin and ellagic acid are phenolic compounds found in Q. robur. The heartwood contains triterpene saponins.Similar species
Q. robur is most likely to be confused with sessile oak, which shares much of its range. Distinguishing features of Q. robur include the auricles at the leaf base, the very short petiole, its clusters of acorns being borne on a long peduncle, and the lack of stellate hairs on the underside of the leaf. The two often hybridise in the wild, forming Quercus × rosacea.Turkey oak is also sometimes confused with it, but that species has "whiskers" on the winter buds and deeper lobes on the leaves. The acorn cups are also very different.
Taxonomy
Quercus robur was named by Carl Linnaeus in Species Plantarum. It is the type species of the genus and classified in the white oak section.The genome of Q. robur has been completely sequenced ; the first version was published in 2016. It comprises 12 chromosome pairs, about genes and 750 million bp.
There are many synonyms, and numerous varieties and subspecies have been named. The populations in Iberia, Italy, southeast Europe, and Asia Minor and the Caucasus are sometimes treated as separate species, Q. orocantabrica, ''Q. brutia Tenore, Q. pedunculiflora K. Koch and Q. haas Kotschy respectively.
Quercus × rosacea Bechst. is the only naturally occurring hybrid, but the following crosses with other white oak species have been produced in cultivation:
- 'Fastigiata', cypress oak, is a large imposing tree with a narrow columnar habit.
- 'Concordia', golden oak, is a small, very slow-growing tree, eventually reaching, with bright golden-yellow leaves throughout spring and summer. It was originally raised in Van Geert's nursery at Ghent in 1843.
- 'Pendula', weeping oak, is a small to medium-sized tree with pendulous branches, reaching up to.
- 'Purpurea' is another small form, growing to, with purple leaves.
- 'Pectinata', cut-leaved oak, is a cultivar where the leaf is pinnately divided into fine, forward-pointing segments.
Names
Distribution
The species is native to most of Europe and western Asia, and is widely cultivated in other temperate regions.Habitat and ecology
Pedunculate oak is a long-lived tree of high-canopy woodland, coppice and wood pasture, and it is commonly planted in hedges. It is rare on thin, well-drained calcareous soil. Sometimes it is found on the margins of swamps, rivers and ponds, showing that it is fairly tolerant of intermittent flooding.Image:Wistman's Wood in winter.jpg|thumb|Ancient pedunculate oaks at Wistman's Wood in Devon, England
Its Ellenberg values in Europe are L = 7, T = 6, F = 6, R = 5, N = 2-6 and S = 0, which describe how it favours conditions of bright sunlight, moderate temperature, moisture and pH, a wide range of nutrient levels, and low salinity.
In 2019 it was estimated that 2,300 species of insect, bryophyte, lichen, bird, mammal or other species are associated with Q. robur in the UK. Some entirely rely on it while other can make use of other tree species. Within its native range, Q. robur is valued for its importance to insects and other wildlife, famously supporting the highest biodiversity of insect herbivores of any British plant. The most well-known of these are the ones that form galls, which number about 35. The knopper gall is very common, and Andricus grossulariae produces somewhat similar spiky galls on the acorn cups. Also common are two types of spherical galls on the twigs: the oak marble gall and the cola nut gall. The latter are smaller and rougher than the former. A single, large exit hole indicates that the wasp inside has escaped, whereas several smaller holes show that it was parasitised by another insect, and these emerged instead. The undersides of oak leaves are often covered in spangle galls, which persist after the leaves fall.
One of the most distinctive galls is the oak apple, a 4.5 cm diameter spongy ball created from the buds by the wasp Biorhiza pallida. The pineapple gall, while less common, is also easily recognised.
The quantity of caterpillar species on an oak tree increases with the age of the tree, with blue tits and great tits timing their egg hatching to the leaves opening. The most common caterpillar species include the winter moth, the green tortrix and the mottled umber, all of which can become extremely abundant on the first flush of leaves in May, but the oak trees do recover their foliage later in the year.
The acorns are typically produced in large quantities every other year and form a valuable food resource for several small mammals and some birds, notably Eurasian jays Garrulus glandarius. Jays were overwhelmingly the primary propagators of oaks before humans began planting them commercially, because of their habit of taking acorns from the umbra of its parent tree and burying them undamaged elsewhere.
Diseases
- Acute oak decline
- Powdery mildew caused by Erysiphe alphitoides
- Sudden oak death
Uses
Additionally, although bitter due to their high tannin content, the acorns can be roasted and ground into a coffee substitute.
In culture
In the Scandinavian countries, oaks were considered the "thunderstorm trees", representing Thor, the god of thunder. A Finnish myth is that the World tree, a great oak which grew to block the movement of the sky, sunlight and moonlight, had to be felled, releasing its magic, thus creating the Milky Way. The oak tree also had a symbolic value in France. Some oaks were considered sacred by the Gauls; druids would cut down the mistletoe growing on them. Even after Christianization, oak trees were considered to protect as lightning would strike them rather than on nearby inhabitation. Such struck trees would often be turned into places of worship, like the Chêne chapelle.In 1746, all oak trees in Finland were legally classified as royal property, and oaks had enjoyed legal protection already from the 17th century. The oak is also the regional tree of the Southwest Finland region.
During the French Revolution, oaks were often planted as trees of freedom. One such tree, planted during the 1848 Revolution, survived the destruction of Oradour-sur-Glane by the Nazis. After the announcement of General Charles de Gaulle's death, caricaturist Jacques Faizant represented him as a fallen oak.
In Germany, the oak tree can be found in several paintings of Caspar David Friedrich and in "Of the life of a Good-For-Nothing" written by Joseph Freiherr von Eichendorff as a symbol of the state protecting every citizen.
File:Gornji-milanovac-grb.png|thumb|upright=0.75|The oak in the coat of arms of Gornji Milanovac, Serbia
In Serbia the oak is a national symbol, having been part of the historical coat of arms of the Socialist Republic of Serbia, the historical coat of arms and flags of the Principality of Serbia, as well as the current traditional coat of arms and flag of Vojvodina.
Image:Zapis-0454-Kolare-hrast-luznjak-spomenik-prirode 20150828 1335.jpg|thumb|A sacred pedunculate oak tree in the settlement of Kolare in Jagodina, Serbia
In England, the oak has assumed the status of a national emblem. This has its origins in the oak tree at Boscobel House, where the future King Charles II hid from his Parliamentarian pursuers in 1650 during the English Civil War; the tree has since been known as the Royal Oak. This event was celebrated nationally on 29 May as Oak Apple Day, which continues to this day in some communities.
Many place names in England include a reference to this tree, including Oakley, Occold and Eyke. Copdock, in Suffolk, probably derives from a pollarded oak. 'The Royal Oak' is the third most popular pub name in Britain and HMS Royal Oak has been the name of eight major Royal Navy warships. The naval associations are strengthened by the fact that oak was the main construction material for sailing warships. The Royal Navy was often described as "The Wooden Walls of Old England" and the Navy's official quick march is "Heart of Oak". In folklore, the Major Oak is where Robin Hood is purported to have taken shelter.
Oak leaves have been depicted on the Croatian 5 lipa coin; on old German Deutsche Mark currency, and now on German-issued euro currency coins ; and on British pound coins.
In Northern Ireland, the city of Derry, and the county of Londonderry, is an anglicisation of the Irish Daire or Doire, which translates as 'oak-grove/oak-wood'.