Worms are often overlooked. And yet these ecosystem engineers are crucial for our gardens. In an organic garden, you soon discover that you do not garden alone. You rely on a bevy of other creatures, all of whom also ‘garden’ in some way and contribute to the whole.
The worms in your garden, whether you are aware of them or not, are helping you as a gardener in a range of different ways. It is time we celebrated this incredible creature. So here are some facts about humble earthworms, so you can appreciate them more and encourage them in your garden.
Why Worms Are Useful in the Garden
Worms help in the garden by:
Loosening, aerating and breaking up compacted soil. (By making their tunnels through it.)
Helping to break down organic matter. (By eating decaying matter.)
Distributing that organic matter. (Redistributing soil and organic matter as they ‘poo’.)
Worm poo, or worm castings, are a mix of soil and organic matter. They fertilize the topsoil and improve its texture.
The presence of earthworms in soil also has a positive effect on bacteria and fungi. There are more of these beneficial micro-organisms and they are more active. This is very important since bacteria and fungi are key in releasing nutrients from organic matter and making them available to plants.
Worms are also an important food source for other soil based animals, and for other wildlife that lives in your garden. So having plenty of worms helps boost biodiversity and makes for a stronger and more resilient garden ecosystem overall.
Sometimes, worms are also used specifically in making compost. Gardeners introduce worms to a wormery where scraps and other organic matter is broken down.
What Are Earthworms?
We’ve all surely seen earthworms in our gardens. But though they are a familiar sight, you might not know much about them at all.
Earthworms are a specific group of invertebrates included within the taxonomic phylum Annelida. There are around 16 species of earthworms typically found in gardens in the UK, and 27 species in total can be found here. These vary while a lot in their size and colour. But all help in the garden.
Three major ecological groups of earthworms have been identified based on the feeding and burrowing behaviours of common earthworms in the British Isles. Though not all worms conform to one of these types, the types can be used to understand the different species and their variety a little better.
Anecic Earthworms – These make permanent vertical burrows in soil. They are the largest type of earthworm in the UK and you may see their casts on lawns. They feed on leaves on the soil surface that they drag into their burrows.
Endogenic Earthworms – These earthworms live in and feed on the soil. Some burrow very deeply. They move around, making new tunnels and reusing existing tunnels as they feed.
Epigeic Earthworms – These live on the soil surface in leaf litter and tend not to make burrows. They live in and feed on decaying organic matter.
In addition to these three ecological groups of worms, other worms that gardeners are likely to encounter are compost worms.
Compost earthworms live, in the name suggests, in compost. And are also found in areas where there is a lot of most, rotting vegetation. These worms exist naturally in environments. But gardeners also deliberately introduce these species to their composting systems when they are setting them up. Using compost worms to make compost is called vermicomposting.
An earthworm is made up of a digestive tube encased within a cylindrical muscular tube that forms its body. The body is divided into segments, which are marked by furrows on the surface. The first segment has the mouth, which has a fleshy muscular lobe on the top. This can be pulled in to seal the mouth, or pushed forwards to probe the immediate surroundings. All of the other segments have retractable bristles which help the earthworm grip and gain traction as it moves.
At the head end of an earthworm there is a muscular area containing a tiny, pin-sized brain, cesophagus and pharynx. Moving down the worm, there are a series of thickenings in their blood vessels that act like hearts. They typically have a number of these pseudohearts – often five pairs in British earthworms.
One other interesting thing about the blood system in earthworms is that, like us, but unlike most invertebrates, worms have haemoglobin in their blood.
Earth worms are hermaphroditic (with both male and female organs in one body). But still need other another earthworm to reproduce. There are organs for the storage of the worm’s own sperm, and spermatacea, where they store the sperm collected from another worm during reproduction.
Earthworms, like birds, have a crop and gizzard, where food collects and is ground down. Food then passes into the rest of their digestive system and out the other end.
How Do Worms Breathe?
You might have noticed in this description that we did not describe any lungs. Earthworms actually breathe through their skin. This is why they are often seen on the surface when it rains. If they do not come to the surface, they risk drowning.
How Do Worms See?
Earthworms do not have eyes either. However, they can sense light and dark and prefer dark conditions because they are easily damaged by the sun’s rays and will dry out quickly.
The Life Cycle of Earth Worms
The life cycle of the earthworm begins with an egg. Eggs are within a casing called a cocoon that may house one to dozens of eggs. (Though just one egg in most species.) The cocoon is formed from the skin of the clitellum, that comes off an earthworm like a snake’s skin, capturing the fertilized eggs and creating a protective sac.
Hatchlings (tiny, thread-like worms) come from these eggs, often in spring. Juveniles grow and develop their colour if pigmented. Worms hatched in the spring reach maturity in the autumn. They are then capable of reproduction.
Two earthworms reproduce by producing a slime tube and gripping into one another using the tubercula pubertatis (on their saddle). The two worms exchange sperm and store it for later use. Both are male and female during the reproduction. Following this sperm exchange the earthworms separate. A mucus sheath forms around the clitellum. It is moved along the earthworm until it comes off at the head end, carrying the egg or eggs and sperm from the earthworm it mated with. This forms the cocoon within which fertilisation occurs.
What Eats Earthworms
Many beneficial creatures in a garden ecosystem eat earthworms, including:
Ground beetles, flatworms and centipedes.
Amphibians and reptiles. (Toads, newts, slow worms, lizards, grass snakes etc..)
Many different birds.
Rodents, hedgehogs, foxes, badgers, stoats, pine martens and other mammals.
So the more earthworms you have in your garden, the more likely you are to attract and keep a wide range of other wildlife around to help you in your gardening endeavours.
How To Encourage Earthworms in Your Garden
To encourage earthworms and boost their population in your garden:
Garden organically (don’t use any harmful chemicals).
Take a ‘no dig’ approach, disrupting the soil as little as possible.
Make sure there is plenty of organic matter in your soil.
Leave some undisturbed organic matter/ leaf litter around on the soil surface.
Use mulches in growing areas to keep the soil protected, moist and cool.
If you adopt an organic, no dig approach and care for the soil, earthworms will arrive to help you continue to improve the soil, and soil biota will thrive. Other wildlife will arrive and help you in your garden. Earthworms might not be the most appealing creatures that we see in our gardens. But they certainly are amazing things. And all gardeners should learn to appreciate them more.
How many earthworms do you observe in your garden? Let us know in the comments below, and consider doing some citizen science to increase our understanding of earthworms and all that they do.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.