In Britain there are two native species of oak: the English oak and the Sessile oak. Telling them apart is simple, just take a close look at their leaves and acorns. English oak leaves have a very short stalk while Sessile oak leaves have a long one, and conversely, English oak acorns grow at the end of long stalks while Sessile oak acorns have no stalks.

Both species can reach a grand old age – oaks over 1,000 years old can be found around the country – and anything over 400 years old is classed as an ‘Ancient Tree’. With increasing age, oaks become shorter and wider, developing gnarly crevices and hollows.

Oaks are well known for supporting a huge variety of wildlife

As they age they attract even more species. Specialist insects feed on the dead and decaying wood within an aged oak, and many birds and bats use their holes and cavities for nesting and roosting.

Research published by the UK Centre for Ecology and Hydrology in 2019 revealed that mature oak trees support a staggering 2,300 different wild species. Throughout the year in every season, oaks offer valuable living accommodation, food and shelter for a wide variety of wildlife.

Oaks flower in springtime, producing long, pollen-rich green catkins – these are the male flowers. Their pollen is dispersed by the wind, fertilising the small red female flowers, which then grow into acorns. Oak flowers and pollen provide food for a host of creatures, from squirrels to butterflies. The caterpillars of the dazzling purple hairstreak butterfly feast on oak flower buds and leaves, while many bee species rely on oak pollen to provide a springtime buffet.

Image: Don Morris

If you’ve ever seen an unusual shaped growth on an oak tree, you’ve probably stumbled across a gall. Oaks play host to a variety of galls, the most common ones being the oak apple gall, oak marble gall and oak knopper gall. These galls are caused by wasps who lay their eggs onto different parts of the tree. The resulting larvae produce chemicals which cause a distortion in the growth of the tree. The resulting galls vary in shape and size from perfect spheres, like the oak marble gall, to knobbly, walnut-shaped growths like the knopper gall. Galls provide a protective home and food for the larvae growing inside. Once the larvae is ready to emerge from the gall, it will fall off the tree, and you can discover woody, spent galls underneath oaks during summer and autumn. Look for a telltale hole on the outside where the insect growing inside has tunnelled out.

Oak trees provide wild creatures with another gift to help them survive the winter months

In autumn mammals and birds from badgers to woodpeckers feast on the acorn bounty produced by oaks. Acorns are a firm favourite of jays – and these attractive birds also play a part in planting the next generation of oak trees too. Jays store acorns in preparation for winter, and inevitably sometimes forget the locations of their cache, allowing them to germinate the following spring.

Even as the oak drops its leaves on the ground in autumn it provides a valuable resource for wildlife. The layer of leaves on the woodland floor is like a winter duvet, offering protection in the cold months for countless invertebrates. Many of these creatures break down the leaves and other natural debris through feeding, nourishing the woodland soil beneath.

Trees with a long history growing a brighter future...

In the Forest of Marston Vale, we have planted thousands of oaks, which not only benefit wildlife but people too. As oaks grow, they absorb atmospheric carbon dioxide, helping us to tackle the impacts of climate change. Although slow-growing, because of their size and longevity oaks are one of the best long-term stores of carbon.

The iconic oak tree has been by our side throughout history – providing us with strong building materials to get us through wars and fuel to keep us warm. Now oaks stand by us again as we face another of humanity’s biggest challenges – the climate emergency and biodiversity crisis.

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