English Oak / Quercus robur ( Latin quercus, "oak" + robur "strength, hard timber") is a large deciduous tree, with a circumference of mature oaks averaging 4-6m.
Quercus robur has lobed and nearly sessile (very short-stalked) leaves 7–14 cm long. Flowering takes place in mid spring, and the fruit, called acorns, ripen by mid autumn.
Quercus robur is very tolerant to soil conditions and the continental climate but it prefers fertile and well-watered soils. Mature trees tolerate flooding.
It is a long-lived tree, with a large wide spreading 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.
A close relative is the sessile oak (Q. petraea), which shares much of its range. Quercus robur is distinguished from this species by its leaves having only a very short stalk (petiole) 3–8 mm long, and by its pedunculate (stalked) acorns. The two often hybridise in the wild, the hybrid being known as Quercus × rosacea.
The acorns form a valuable food resource for several small mammals and some birds, which and still remain the principal propagators for wild oaks because of their habit of taking acorns from the umbra of its parent tree and burying them undamaged elsewhere. Mammals, notably squirrels who tend to hoard acorns and other nuts usually leave them too abused to grow in the action of moving or storing them.
Quercus robur is a member of the white oak section. Quercus robur should not be confused with Q. rubra, the red oak, which is a native of North America and only distantly related.
Quercus robur 'Fastigiata' (Cypress Oak / Pyramid Oak), probably the most common cultivated form, it grows to a large imposing tree with a narrow columnar habit. The fastigiate oak was originally propagated from an upright tree that was found in central Europe.
Quercus robur 'Pendula' (Weeping Oak), a small to medium-sized tree with pendulous branches, reaching up to 15m.
Quercus robur 'Purpurea' (Purple English Oak) is another cultivar growing to 10m, but with purple coloured leaves.