Oak, English (Quercus robur)

A large, deciduous tree growing up to 20–40m tall. Also known as common oak, this species grows and matures to form a broad and spreading crown with sturdy branches beneath.

Look out for: its distinctive round-lobed leaves with short leaf stalks (petioles).

Identified in winter by: rounded buds in clusters. Each bud has more than three scales.

What does English oak look like?

Not to be confused with:

Sessile oak (Quercus petraea). Its leaves have stalks and its acorns don’t have stalks (whereas it’s the opposite in English oak which has tiny or no leaf stalks and acorns on longer stalks).

Where to find English oak

English oak is a very common tree. It is especially common in deciduous woods in southern and central Britain. In fact, it’s so frequent that it has assumed the status of a national emblem.

Value to wildlife

Oak forests support more life forms than any other native forest. They are host to hundreds of insect species, supplying many birds with an important food source. In autumn, mammals such as squirrels, badgers and deer feed on acorns.

Flower and leaf buds of English oak are the food plants of the caterpillars of purple hairstreak butterflies.

The soft leaves of English oaks break down with ease in autumn and form a rich leaf mould beneath the tree, supporting invertebrates such as the stag beetle, and fungi, like the oakbug milkcap. Holes and crevices in the tree bark are perfect nesting spots for the pied flycatcher, redstart or marsh tit.

Bats also roost in old woodpecker holes or under loose bark, as well as feeding on the rich supply of insects in the tree canopy.

Mythology and symbolism

The oak was sacred to many gods, including Zeus, Jupiter and the Celtic Dagda. Each of these gods ruled over thunder and lightning, and oak trees are often hit by lightning as they are the tallest living feature in the landscape.

Druids practised rituals in oak groves and cherished the mistletoe that grows in oak-tree branches. It’s also linked with royalty: ancient kings and Roman Emperors wore crowns of oak leaves.

In England, the oak is a national symbol of strength. Couples were wed under ancient oaks in Oliver Cromwell’s time. Oak is the emblem of many environmental groups, including the Woodland Trust.

Uses of English oak

Oaks produce one of the hardest and most durable timbers on the planet. However, it takes up to 150 years before an oak is ready to use in construction. It has been a prized hardwood timber for thousands of years and is still used for flooring, wine barrels and firewood.

Other uses of oak:

• Leaves, bark and acorns were believed to heal many medical ailments, including diarrhoea, inflammation and kidney stones.
• Acorns have also been used to make flour for bread making.
• Tannin found in the bark has been used to tan leather since at least Roman times.

Threats and conservation

Acute oak decline and chronic oak decline are serious conditions affecting Britain’s oaks, with several contributing factors linked to the diseases. Decline of mature oaks first aroused concern in the 1920s and today most cases are in central, southern and eastern England.

The oak processionary moth is a non-native pest that has been found in London, Surrey and Berkshire. Not only does it damage the foliage of the trees and increase the oak’s susceptibility to other diseases, it is actually a risk to human health. The moth's hairs are toxic and can lead to itching and respiratory problems.