Quercus 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 crown 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. The Bowthorpe Oak in Lincolnshire, England is estimated to be 1,000 years old making it the oldest in the UK, although there is Knightwood Oak in the New Forest which is also said to be as old.
The leaves usually start to open in the middle of April, with male and female flowers following. Male flowers are yellow catkins that dangle down, and female flowers are small and red. The flowers develop into nuts called acorns, wich continue developing until they ripen in October. The acorns of English oak have a long stalk called a Peduncle.
In late summer, Oak trees often produce a second spurt of growth called Lammas growth. Lammas growth shoots are often longer.
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. Q.robur supports the highest biodiversity of insect herbivores of any British plant (>400 spp). The acorns 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 it undamaged elsewhere. Mammals, notably squirrels who tend to hoard acorns and other nuts most often leave them too abused to grow in the action of moving or storing them. Many species of invertebrates feed on oak, including the Common Quaker, and some species have evolved to look like an oak leaf, for example the Lappet Moth.
English oak timber is used for a variety of things. It is used for building timber, fence posts, other planks, and was popular shipbuilding material before metal was used. However, only the heartwood of the tree can be used for this. The sapwood rots within a few years.
Oak is quite a slow growing tree, and is also planted as standard trees with Hazel trees, as part of the "coppice with standards" method of woodland management.