Simple tube-like creatures made up of a digestive tract housed within a slimy skin, the humble earthworm is a garden hero and crucial composter. They transform the ground through which they move into rich, fertile soil capable of supporting all kinds of vegetable life. Charles Darwin called them “ploughs of the earth” and folk names include the rather poetic “night crawler” and “dew-worm”, highlighting these tiny tillers’ deep love of the damp and dark.
If your garden plays host to a large and active population of earthworms, then your soil is likely to be fertile, well aerated and good at retaining moisture. Worms break down large pieces of organic matter into rich humus. They’ll happily eat away rotting plant material, animal parts, bacteria and fungi, but they never feed on healthy plants. They pull the matter below the ground, shred it into smaller pieces and partly digest it. They produce excrement called castings, a vermi-compost that is extremely nutritious. Every day worms produce nitrogen, phosphorous, potassium, calcium carbonate and many other micro nutrients in a form that all plants can use.
Generally nocturnal, earthworms are usually found in the top 10cm of soil but they will burrow deeper if the topsoil is too dry, happy to tunnel two metres down if necessary. They favour cool temperatures and aren’t fans of sandy or acidic soil. Worms don’t have eyes, noses or lungs but they can have up to five pairs of hearts. They breathe through their skin, while their mouth cavity connects directly into the digestive tract with no intermediate processes.
Worms are mainly muscle and travel underground by contractions that alternately shorten and lengthen the body. They’re made up of many small segments known as annuli. These are ridged and covered with tiny claw-like bristles that give them good grip. You’ll have noticed that worms all sport a saddle, about a third of the way along their length, known as the clitellum. This is where the clear mucus that makes worms slippery and slimy, and so better able to burrow, is secreted from. The worm’s burrowing is as important for good soil health as their composting. Their movements mix the soil, aiding plants uptake of minerals, and their tunnels allow water to better penetrate the earth.
The country’s worms need you
The importance of worms has long been appreciated, not least because Darwin devoted a great deal of study to them, pondering whether there “are many other animals which have played so important a part in the history of the world”. Despite such stellar attention, many basic questions about earthworm ecology and distribution remain unanswered. For this reason, a far reaching survey has launched this spring to build up an accurate picture of the UK worm population. Organised by OPAL, the Open Air Laboratories Network, people across the country are being asked to survey their allotment, garden, park or playing field for earthworms.
You can download a worm survey guide from www.OPALexplorenature.org. Once you’ve completed the survey, you can upload your results on to an interactive map. The survey will produce a massively useful bank of data for scientists and will ultimately feed into the very first community-led study of the natural world.
Worms are amazing
Emma Sherlock is Invertebrates Curator at the Natural History Museum and knows a thing or two about the worm. She delights in telling me about the metre long Australian worm she has in her collection, although she can get pretty excited about native worms too. “You can dig up huge red ones about as long as a school ruler, there are small stumpy green ones and even striped ones in the compost heap that give off a sticky yellow acid if you irritate them”.
She says earthworms could be great indicator species and could help scientists monitor the effects of climate change. This is why it’s crucial that an accurate picture of what worms are where is built up through the OPAL survey. “Once we have baseline data for the UK, the worms can start telling us a lot more” explains Emma.
“Once the data is in, then we can start analysing it. We’ll be able to produce maps of the common species in the UK and study the occurrence of the species in relation to the habitat and soil type it was collected in. This will give us an idea of the ranges of species and their tolerances.”
Worm friendly gardening
It’s clear that any fruit and vegetable grower should want to attract worms into their patch, as healthy worm rich soil means well nourished plants producing handsome crops. A small wildlife friendly garden can be home to literally thousands of worms. One way to attract them is to become a devotee of mulch. You can download a free guide to mulching at www.wildlondon.org.uk/gardening
Trying to be a ‘no dig’ gardener is another way to make your patch more attractive to worms. Undisturbed, hard working worms should do your digging for you. If you have acidic soil, which worms don’t like, adding lime can help. And apparently worms are partial to mint, so perhaps try growing a few plants in areas where you’d like more worm activity.
“Worms will arrive in any garden and you’ll find different species living in your compost heap, your lawn and your borders” says worm expert Emma Sherlock. “To encourage different species in your garden, try and make different little microhabitats. So as long as you don’t add pesticides, don’t have too much drainage, so the soil is very dry, and don’t plough your land, then earthworms should thrive”.
Fascinating worm facts
There are at least 25 native species of earthworm in the UK
Earthworms are hermaphrodites
Earthworms can regenerate lost segments
The belief you can chop a worm in half to make two is a myth
Some earthworms gurgle as they move through the earth
Worms can’t see or hear
Worm fossil casts have been found dating back more than 600 million years
This article appears in the May issue of Kitchen Garden magazine