Sometimes the best thing we can do for nature in the garden is to do nothing. That's been the theme of our Do Nothing for Nature campaign, where we're showing gardeners how nature doesn't always need us to buy more plants and do more work. This doesn't have to apply to the whole garden - you can easily create wild areas where nature is allowed to do its own thing.
One of the most under-rated resources for wildlife in the garden is fallen wood. In natural habitats, dropped branches and downed trees can be a kind of windfall that insects, fungi and plants have evolved to exploit. Some insects are only found in or around rotting wood, so the simple task of leaving wood to decay is a quick way of boosting the wildlife in your garden.
Beetles are some of the first insects to find decaying wood. In gardens we are likely to find a range of Ground Beetles and Rove Beetles. There are over 1300 species of these in the UK, but some of the distinctive garden species include the Violet Ground Beetle which is quite large, with a violet sheen to its body, and the Black Clock Beetle which is mostly black with strong ridges along its wing-case. The reason I mention both of these is that they are true friends of the gardener - they are predators that eat snails and slugs, amongst other things! To encourage insects like these, all you need to do is leave some wood on soil, and they will do the rest.
Even bees can make use of fallen wood. Leafcutter bees are a special group of solitary bees (meaning there is no queen in the nest). Females of species like the Patchwork Leafcutter bee excavate burrows into dead wood to make nests. They can be seen cutting sections of leaves and flowers and flying back to the nest with them, where she arranges them to make the walls of 'cells'. The nest has many cells, each with an egg and a supply of food for the young bee when it hatches. These bees also use the 'bee hotels' with canes, but you can make your own by leaving wood to decay or drilling holes up to 11mm in diameter into logs in sunny positions.
Leaving stacks of wood can be of greater benefit to butterflies and moths than just single logs. Think of it as being a high-rise block of flats where different niches provide homes for a wider variety of residents. In these stacks you might find caterpillars that have crawled inside to overwinter or pupate. Some species of butterfly such as the Peacock, Comma and Small Tortoiseshell actually overwinter as adults. The undersides of their wings are dark black and brown so they look just like dead leaves when they shut their wings together.
It's best to use wood from your own or your neighbours' gardens if you can, and avoid using wood that has been treated with any chemicals to preserve it, as those preservatives may cause harm to insects and fungi in the soil.
However you go about it, whether you have a single decaying log or a stately stack of sticks, providing this vital resource is a simple way to get your garden thriving, and another way to Do Nothing for Nature.