Britain has about 16 species of earthworms likely to be found in gardens. They vary in size and colour but all have a role to play in soil processes.
Earthworms eat decaying plant material; they do not damage growing plants, and are important to soil structure and fertility. Some earthworms emerge at night to feed on dead plant material on the surface, and pull fallen leaves and other plant debris into their tunnels. Some species such as Allolobophora nocturna, A. longa and Lumbricus terrestris live in permanent burrows and it is mainly these species that produce worm casts on the surface. Worm casts consist of soil and waste excreted by the worms as they feed on organic matter. They can be a nuisance on lawns and gravel paths.
Earthworms can be active throughout the year but are quiescent during cold, hot and dry weather. They occur in most soils but are scarce in soils that are extremely acidic or prone to waterlogging.
Specialist species
Some earthworm species live in accumulations of organic matter, such as compost heaps. One such species is Eisenia foetida (brandling or tiger worm), recognisable by its stripy appearance, another is Dendrobaena veneta. These are the species most commonly used in wormeries, as their activities speed up the composting process.
Andrew Halstead