Why Native Trees Matter to Britain's Insects

Walk any hedgerow or woodland edge in May and you are walking through a larder that has been stocked for thousands of years. Our native trees have evolved alongside British insects for so long that many caterpillars, beetles and mining flies depend on one particular species to complete their life cycle. A non-native ornamental may look handsome, but it offers little to the local menu. If you want your garden, smallholding or community patch to buzz and flutter, the answer is usually an oak, a willow or a birch.

Let us look at those three champions first, and then at a few supporting players you can plant alongside them.

Oak: The Undisputed Favourite

No other British tree supports such an extraordinary range of insects. The English oak (Quercus robur) and sessile oak (Quercus petraea) together play host to several hundred species, more than any other native tree in these islands. Purple hairstreak butterflies, oak bush-crickets, gall wasps, nut weevils and a whole guild of leaf-mining moths all rely on oak foliage and timber.

Oaks are also generous in ways you might not expect. Their catkins provide early pollen, honeydew from aphids feeds hoverflies and wasps, and the deep crevices of a mature oak's bark are perfect roosting sites for bats and hibernating ladybirds.

• Best for: caterpillars, oak-associated moths, acorn weevils, stag beetles around aged trees
• Planting note: grow from locally collected acorns or buy British-grown bare-root stock; oaks are slow but long-lived, so think in decades
• Space needed: allow plenty — a mature oak can dominate a small garden

Willow and Sallow: Early Food and a Caterpillar Larder

If I could plant only one group of trees for wildlife, it would be the willows. Goat willow, grey willow and their close cousins flower early in spring, often in March, when queen bumblebees and solitary bees are newly emerged and desperate for nectar. Those silky grey catkins are one of the most valuable early-season resources in the British countryside.

The leaves matter just as much. Willows support a remarkable number of associated insects, including the caterpillars of the puss moth, the eyed hawk-moth and the sallow kitten moth. Purple emperor butterflies famously favour sallow, and willow foliage is a favourite for leaf beetles and sawflies.

• Best for: early pollinators, moths, caterpillars, willow gall sawflies
• Planting note: willows root easily from cuttings pushed into damp ground in late winter
• Caution: they are thirsty and fast-growing — keep them away from drains and foundations, and coppice regularly to keep them bushy

Birch: A Pioneer That Feeds Hundreds

Silver birch and downy birch are the trees that turn bare ground into woodland. They are quick to establish, tolerant of poor acid soils and cold upland sites, and they support a large community of insects. Birch supports hundreds of invertebrate species, from the handsome birch shieldbug to the striking buff-tip moth, whose caterpillar mimics a birch twig so convincingly that you can stare straight at it and see nothing.

Birch catkins feed pollen beetles and early bees, while the peeling bark shelters overwintering insects and spiders in its many layers.

• Best for: pioneering bare ground, moths, shieldbugs, aphids that in turn feed tits and warblers
• Planting note: ideal for light, sandy or peaty soils; plant in groups of three or more for a natural look
• Seasonal bonus: autumn leaf litter breaks down quickly, feeding the soil web beneath

Supporting Players Worth Space

If your plot is small, do not despair — you do not need an oak wood to make a real difference. Several smaller natives punch well above their weight.

• Hawthorn: supports well over a hundred insect species and its May blossom is a magnet for bees and hoverflies. Excellent for hedges.
• Blackthorn: early sloe blossom comes just ahead of hawthorn, filling a hungry gap for pollinators.
• Alder buckthorn: the essential food plant of the brimstone butterfly caterpillar, plus superb nectar for bees.
• Wild cherry: spring blossom for pollinators and cherries for birds and mammals.
• Hazel: coppices readily and its leaves feed the caterpillars of several prominent moths.
• Alder: perfect for wet ground, with nitrogen-fixing roots that improve the soil around it.

Planting for a Year-Round Larder

Think in layers and seasons rather than a single tree. A mix that flowers and leafs at different times will support insects from February through to November. Aim for at least three or four native species if space allows, and let some leaves lie where they fall — many moths and beetles overwinter in leaf litter.

Plant bare-root trees between November and March, when they are dormant and the soil is workable. Dig a hole wider than it is deep, spread the roots, and set the tree at the same depth it grew in the nursery — the old soil mark on the trunk is your guide. Firm gently, water well in the first two summers, and mulch with well-rotted compost or bark, keeping the mulch clear of the trunk.

Protect young trees from rabbits and deer with a sturdy guard, but leave the base clear of dense grass so insects can reach the bark. Avoid staking unless the site is exposed, and never use weed membrane right up to the trunk.

Above all, be patient. A whip planted this winter will feed aphids next summer, caterpillars the year after, and perhaps a purple hairstreak before you know it. Plant a native tree, and you plant a whole community.