Cornish oak

Quercus petraea
Sessile oak
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Fagales
Family:	Fagaceae
Genus:	Quercus
Section:	Quercus
Species:	Q. petraea
Binomial name
Quercus petraea (Matt.) Liebl.
Distribution map
Synonyms
List Quercus robur var. petraea Matt. 1777 Quercus brevipedunculata Cariot & St.-Lag. Quercus calcarea Troitsky Quercus columbaria Vuk. Quercus coriacea Bechst. Quercus coronensis Schur Quercus decipiens Behlen Quercus dispar Raf. Quercus durinus Raf. Quercus erythroneura Vuk. Quercus esculus L. Quercus longipetiolata Schur Quercus mas Thore Quercus mespilifolia Wallr. Quercus peraffinis Gand. Quercus petiolata Schur Quercus regalis Burnett ex Endl. Quercus sessiliflora Salisb. Quercus sessilis Ehrh. ex Schur Quercus spathulifolia Vuk. Quercus sphaerocarpa Vuk. Quercus sublobata Kit. Quercus huguetiana (Franco & G.López) Rivas Mart. Quercus colchica Czeczott Quercus dshorochensis K.Koch Quercus hypochrysa Steven Quercus iberica Steven ex M.Bieb. Quercus kochiana O.Schwarz Quercus kozlowskyi Woronow ex Grossh. Quercus lamprophyllos K.Koch Quercus polycarpa Schur Quercus sorocarpa Woronow ex Maleev Quercus szowitzii Wenz. Quercus abietum Kotschy ex A.DC. Quercus cedrorum Kotschy Quercus ibicis Kotschy ex A.DC. Quercus pinnatiloba K.Koch Quercus subalpina Kotschy ex A.DC. Quercus tergestina Wenz. plus a long list of invalid names and another long list of names below the species level

Quercus petraea, commonly known as the sessile oak,Cornish oak, or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran.

The sessile oak is an unofficial emblem in Wales and Cornwall.

The sessile oak is a large deciduous tree up to 20–40 m (66–131 ft) 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 (2.8–5.5 in) long and 4–8 cm (1.6–3.1 in) broad, evenly lobed with five to six lobes on each side, and a 1-centimetre-long (0.39 in) petiole. The flowers are catkins, produced in the spring. The fruit is an acorn 2–3 cm (0.79–1.18 in) long and 1–2 cm (0.39–0.79 in) broad, which matures in about six months.

Significant botanical differences from pedunculate oak (Quercus robur) include the stalked leaves, and the stalkless (sessile) acorns from which one of its common names is derived. It occurs in upland areas over 300 m (984 ft) with higher rainfall and shallow, acidic, sandy soils. Its specific epithet petraea means "of rocky places".Quercus 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 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.

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