By best-selling nature writer Sally Coulthard, Woodcuts by Sarah Price.
When Charles Darwin had to pick what he thought was the most important animal in the world he didn’t choose the ape for its intelligence, or the sheep for its usefulness, or the duck-billed platypus for its sheer oddness. He chose the earthworm.
Calling it ‘nature’s plough’, Darwin crowned the humble earthworm the most significant creature on the planet, stating, “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.”
And yet, most of us know almost nothing about these marvellous engineers of the soil. We take them for granted but, without earthworms, life would stop. The world’s soil would be barren – our gardens, fields and farms wouldn’t be able to grow the food and support the crops and animals we need to survive.
Earthworms not only recycle decaying plants, putting nutrients back into the soil, with their endless wiggling and burrowing they also help rain soak away and provide food for wildlife as diverse as foxes to frogs.
Earthworms are heroes in miniature. For too long, we have taken the endless toil of earthworms for granted, without really knowing who’s doing all the work or why.
Take earthworms and wild seeds, for example. Soil is packed full of seeds; when plants drop their seeds not all of them will germinate straight away. Depending on where they land, seeds will either grow, rot or go into dormancy, waiting for the right conditions to thrive. The latter of these seeds inevitably get covered over and worked into the soil, where they can persist for years. It’s a clever strategy and means that plants can survive, in the form of an underground ‘seed bank’, even if conditions above ground won’t support them.
Studies that shown that some species of earthworms eat seeds as they chomp through the soil and leaf litter. By ingesting seeds, and then depositing them on the soil surface in their casts, earthworms are one of the main ways seeds get a chance to come back to the soil surface and grow.
Scientists have also shown that seeds which have passed through the guts of an earthworm have a better chance of germinating than seeds which haven’t – the chemical composition of worm casts seems to give seeds a better chance of germinating. A reverse effect is also beneficial – by burying seeds through their day-to-day activity, earthworms may be key to the formation of large seeds banks in many different ecosystems.
All types of gardens need earthworms for their long term success, so how can we encourage more wrigglers into outdoor spaces?
FEED THE WORMS – The more organic matter you can add to your soil, the more earthworms you’ll have.
In gardens and other growing spaces such as allotments, we tend to take more goodness out of the soil than we put in. We tidy up fallen leaves, pull out dead plants and clear away the natural debris left behind at the season – all the things that would ordinarily contribute to the richness of the soil.
There are a number of ways to add organic matter to soil – homemade compost, shop-bought peat-free compost, municipal compost (from council-run recycling centres), mushroom compost from commercial growers, spent hops from breweries, well-rotted manure, spent coffee grounds, leaf mould, and composted bark.
Apply organic material in spring, before the growing season starts – gardening bodies usually recommend applying organic matter at least 5cm deep but even just a generous sprinkling will help improve the nutrition in the soil for earthworms. Keep adding extra compost every year.
DON’T DIG – Earthworms hate being disturbed.
The endless digging and tilling of soil not only disrupts their natural behaviour (and risks chopping worms in two) but also destroys their burrows. The constant cultivation and turning over of soil also crashes through the delicate soil eco-system – in just one handful of soil there are more living organisms than all the humans on the planet.
In general, you shouldn’t need to aerate soil – earthworms will do that for you. They’ll also drag organic matter on the soil surface down on your behalf. If you must dig, use a fork if possible. It’s also important not to compact the soil by walking over it – practical solutions such as making stepping stones, wooden walkways, raised beds, garden paths and not making overly deep beds all avoid the problem.
WATER WORMS – Earthworms thrive a cool, damp environment.
Adding a decent layer of organic material to your soil will help keep moisture trapped in the soil but it’s also important to water your garden or allotment over the warmer months if the soil gets too dry. Always water in the early morning, or early evening, when the weather is still cool. This not only stops too much of the water being evaporated by the heat of the day but it also prevents pollinating insects such as bees and butterflies from feeling the full force of a hose pipe.
Find out more about the fascinating and hidden lives of earthworms in Sally Coulthard’s The Book of the Earthworm £9.99 (Head of Zeus) – also available The Hedgehog Handbook and The Bee Bible.