Quercus robur (sometimes considered Q. pedunculata) is commonly known as the pedunculate oak or English oak. It is native to most of Europe, and to Asia Minor to the Caucasus, and also to parts of North Africa.
A close relative is the Sessile Oak (Q. petraea), which shares much of its range. Q. robur is distinguished from this species by its leaves having only a very short stalk 3–8 mm long, and by its pendunculate acorns. The two often hybridise in the wild, the hybrid being known as Quercus × rosacea.
Q. robur is a large deciduous tree 25–35 m tall (exceptionally to 50 m), with lobed and nearly sessile (very short-stalked) leaves 7–14 cm long. Flowering takes place in mid spring, and their fruit, called acorns, ripen by the following autumn. The acorns are 2–2.5 cm long, pedunculate (having a peduncle or acorn-stalk, 3–7 cm long) with one to four acorns on each peduncle.
It is a long-lived tree, with a large widespreading head of rugged branches. While it may naturally live to an age of a few centuries, many of the oldest trees are pollarded or coppiced, both pruning techniques that extend the tree's potential lifespan, if not its health. A specimen of notable longevity is one in Stelmužė, Lithuania which is believed to be approximately 1,500 years old, possibly making it the oldest oak in Europe; another specimen, called the Kongeegen (Kings Oak), estimated to be about 1,200 years old, grows in Jaegerspris, Denmark. Yet another can be found in Sweden, Kvilleken. It is over 1,000 years old and 14 meters around. Of maiden (not pollarded) specimens, one of the oldest is the great oak of Ivenack, Germany. Tree-ring research of this tree and other oaks nearby gives an estimated age of 700 to 800 years old.
Within its native range Q. robur is valued for its importance to insects and other wildlife. Numerous insects live on the leaves, buds, and in the acorns. The acorns form a valuable food resource for several small mammals and some birds, notably Eurasian Jays Garrulus glandarius.
It is planted for forestry, and produces a long-lasting and durable heartwood, much in demand for interior and furniture work. The wood of Q. robur is easily identified just by taking a closer look at the cross-section perpendicular to fibres. The wood is characterised by its distinct (often wide) dark and light brown growth rings. The earlywood displays a vast number of large vessels (~0.5 mm diameter). Rays which resemble of thin (~0.1 mm) yellow or light brown lines run across the growth rings.
Along with the naturally occurring Q. × rosacea, several hybrids with other white oak species have also been produced in cultivation, including Turner's Oak Q. × turnerii, Heritage Oak Q. × macdanielli, and Two Worlds Oak Q. × bimundorum, the latter two developed by nurseries in the United States.