English oaks are the most common out of the five oak species in Britain. Only two are native species, although two or more are widely naturalised and many species occur in specialised collections.

The native tree grows quickly during the first hundred years and slows thereafter, reaching 40 metres in height. Oak trees can live over a thousand years. They redirect their energy from their canopy into extending their lifespan and, as a result, shorten with age.

English oaks form a broad and spreading crown with sturdy branches beneath as they mature. The open canopy enables light to penetrate, allowing flowers such as primroses to grow below. Oak trees are home to a rich biodiversity: they host and feed over 280 species of insects and birds.

In urban areas, these include the caterpillar of the purple hairstreak butterfly (which feed on the leaves), marsh tits (which use the holes and crevices in the bark for nests) and bats (which may roost in old woodpecker holes).

In autumn, a layer of decaying leaves forms beneath the tree. This supports invertebrates, including the stag beetle, and many fungi.

Oak trees produce fruits commonly known as acorns. One tree can produce about 25 million acorns in its lifetime. However, it takes 40 years before an oak tree produces its first acorns and about 120 years before peak productivity. Acorns are born on long stalks, a key characteristic that occurs only in this species and helps with identification. Each acorn contains only one seed.