How to promote rot in your garden

Encouraging the army of decomposers, from slugs and snails to beetle grubs, bacteria and fungi, is a great way to enrich your wildlife garden and boost the numbers of visiting animals. 

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Encouraging the army of decomposers, from slugs and snails to beetle grubs, bacteria and fungi, is a great way to enrich your wildlife garden and boost the numbers of visiting animals. Steve Harris explains why it’s time we all learned to love rot.
We all know that composting is a key part of wildlife gardening, but decomposition should also be a more general feature of any garden. As rotting plant material breaks down, it provides a habitat for a wide range of species that do not live anywhere else.
Decomposers, especially slugs, snails, bacteria and fungi, are essential to a healthy environment. In fact, they form the bulk of the species in your garden – 90 per cent of the rotting material you see consists of bacteria and fungi. Though they seldom make their presence felt, decomposers are incredibly important and, being at the bottom of the food web, they underpin the entire ecological system.

When decomposers do show themselves, they can be very attractive. Mushrooms create ‘fairy rings’ in lawns, and colourful fungi sprout from rotting logs. Many beetles lay their eggs in rotten wood, which provides a feast for their growing larvae as they develop; if you’re lucky, stag beetles will be among those that pay you a visit.
But your garden need not be untidy to benefit the army of decomposers – far from it. When covered with ivy or other climbers, log piles are appealing in their own right. And since they need to be kept damp to promote decomposition, they can be hidden away in a quiet corner or under trees where little else will grow.
  • Great tits and other hole-nesting birds will benefit if you leave rotting wood on trees, wherever it is safe to do so.
  • Shaggy ink caps appear on lawns in late summer and autumn, often in groups. Also known as lawyer’s wigs, these fungal fruiting bodies gradually blacken as they age, and then start to decompose.
  • Stag beetle larvae depend on rotting wood for sustenance during their long development. This species is mainly found in southern England.
  • Devil’s coach horses spend the day hidden among rotting vegetation and debris, but come out at night to hunt. They are voracious predators.
  • Millipedes, together with a variety of other invertebrates, flourish in leaf litter left on flowerbeds and in sheltered parts of the garden in winter.
  • Slugs, though not universally liked by gardeners, are a vital part of the wildlife garden. 
  • Wood mice, the commonest of all garden mammals, like to nest under piles of rotting wood. They are hunted by tawny owls and other predators.
  • Sulphur tuft is just one of the many fascinating fungi that grows on rotting logs in gardens, forming large ‘tufts’ that can be seen all year round.
  • Snails thrive on rotting plant material and are a major draw for song thrushes. Heaps of broken shells reveal which snails your local birds prefer.
DECAY IS THE GARDENERS FRIEND: Rotting organic matter is a valuable resource.

It may seem strange to foster decomposition in your garden, but this process forms the base of the food pyramid, as it underpins the whole food web.

Biologists tend to think in terms of food webs – the more links there are in a web, the more species can coexist. This is just as true in a garden as in a tropical rainforest, though perhaps surprisingly, we know little about garden food webs. In general, the greater number of smaller species you have, both in terms of quantity and diversity, the more animals you will have further up the food chain. As links in the chain break, species are lost.

Though most decomposers are not particularly conspicuous, they are superabundant. One estimate suggests that there are 133,000 earthworms per hectare in gardens. And for every slug you see on the surface of the soil, there are another 19 underground, rasping away at plant material and thereby helping with decomposition.

So, when planning your wildlife garden, remember: it’s important to make garden recycling as routine and familiar as recycling household waste.

  • Place logs from a variety of different trees around your garden to ensure a diversity of fungi and minibeasts. They can be hidden behind bushes, covered in ivy or turned into a feature. As they slowly rot, a succession of different types of fungi will add autumnal interest.
  • Keep twigs whenever you trim bushes. Piled up under trees or at the back of flowerbeds, these provide a useful habitat. Make sure they stay damp by watering them or cover them with squares of turf (the wetter they are, the quicker they decompose).
  • Tear up surplus twigs using a shredder (available from garden centres) and spread the chippings on flowerbeds as mulch.
  • Build a stumpery by digging logs from different trees vertically into the ground; this guarantees they stay moist. Fill any nooks and crannies with soil, then plant ferns. A stumpery looks great in a shady part of the garden and is particularly attractive to insects and their larvae.
  • Leave grass cuttings on the lawn as food for earthworms, which in turn attract birds and mammals to the garden. The cuttings will also encourage fungi. Alternatively, spread them over stick piles to keep them wet.
  • Add new logs and stick piles to your garden every year to provide a regular cycle of habitats in different stages of decomposition. Drill holes of different diameters (2–15 mm) into the logs to provide nesting chambers for insects.
  • Leave fallen fruit to rot on the ground. This is a welcome winter feast for birds, including redwings, fieldfares, blackcaps, green woodpeckers and even tits. 


If you enjoyed this, why not read the previous and the next part in the series? 


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