Quercus petraea

Quercus petraea, commonly known as the sessile oak, Cornish oak, Irish Oak or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran. The sessile oak is the national tree of Ireland, and an unofficial emblem in Wales and Cornwall.

Description
The sessile oak is a large deciduous tree up to 40 m tall, in the white oak section of the genus (Quercus sect. Quercus) and similar to the pedunculate oak (Q. robur), with which it overlaps extensively in range. The leaves are 7 - 14 cm long and 4 - 8 cm broad, evenly lobed with five to six lobes on each side and a 1 cm petiole. The male flowers are grouped into catkins, produced in the spring. The fruit is an acorn 2 - 3 cm long and 1 - 2 cm broad, which matures in about six months.

Comparison with pedunculate oak
Significant botanical differences from pedunculate oak (Q. robur) include the stalked leaves, and the stalkless (sessile) acorns from which one of its common names is derived. (With the pedunculate oak, it is the acorns which are pedunculate, i.e. on stalks, while the leaves are not.) It occurs in upland areas of altitudes over 300 m with higher rainfall and shallow, acidic, sandy soils. Its specific epithet petraea means "of rocky places". Q. robur, on the other hand, prefers deeper, richer soils at lower altitude. Fertile hybrids with Quercus robur named Quercus × rosacea are found wherever the two parent species occur and share or are intermediate in characters between the parents.

Charles Darwin, in Chapter II of On the Origin of Species, noted that the sessile and pedunculate oaks had been described as both distinct species and mere varieties depending on the authority consulted.

Taxonomy
Quercus petraea was first described by Heinrich Gottfried von Mattuschka in 1777 as a variety of Quercus robur, Quercus robur var. petraea. It was raised to a full species by Franz Kaspar Lieblein in 1784.

Subspecies
, Plants of the World Online accepted five subspecies:
 * Quercus petraea subsp. austrotyrrhenica Brullo, Guarino & Siracusa
 * Quercus petraea subsp. huguetiana Franco & G.López
 * Quercus petraea subsp. petraea
 * Quercus petraea subsp. pinnatiloba (K.Koch) Menitsky
 * Quercus petraea subsp. polycarpa (Schur) Soó

Diseases and pests

 * Acute oak decline
 * Sudden oak death
 * The Welsh oak longhorn beetle (Pyrrhidium sanguineum) is named after its host tree; the larvae feed at the bark interface of dead wood.

Uses
Sessile oak is one of the most important species in Europe both economically and ecologically. Oak timber is traditionally used for building, ships and furniture. Today the best woods are used for quality cabinetmaking, veneers and barrel staves. Rougher material is used for fence construction, roof beams and specialist building work. The wood also has antimicrobial properties. It is also a good fuel wood. During autumns with good acorn crops (the mast years), animals are traditionally grazed under the trees to fatten them.

Pontfadog Oak
The Pontfadog Oak, once considered to be the oldest oak tree in the UK, was a sessile oak. This grew near Chirk in North Wales. It was understood to be over 1,200 years old, an age that was due to regular pollarding for much of its life. The hollow trunk had a girth of 42 ft. It was lost in April 2013 when it blew down in high winds.