Just when the nation seems to be obsessed with worms, Jane Powers wonders if the snailery is the new wormery.
Who would have thought that wormeries would catch on? Some years ago, the idea of having a container full of worms eating your kitchen waste so that you might collect their droppings to feed to your plants just seemed too squirmy. But now that we're all getting greener and browner by the minute (thanks to pay-by-weight refuse charges), the wormery is becoming as de rigueur as the compost heap.
Furthermore, vermicomposting on an industrial scale is now a reality. In Amy Stewart's recently published book on worms, The Earth Moved, she talks of "continuous flow reactors", huge automated worm bins that can recycle everything from animal manure to food and paper waste.
I made our own small-scale wormery from a half-size plastic dustbin about 15 years ago. And abandoned it a year later, when the ants moved in, and the worms moved out. I know now what I didn't know then: that a successful wormery requires some dedication, and that its inhabitants are choosy about their environment. The correct species for a worm bin is the brandling or tiger worm (Eisenia foetida) - a herd of which I had re-homed from a friend's manure heap.
But, as I discovered, they don't like their billet to be too dry or too moist, or too hot or too cold. They're also finicky about their food. Amy Stewart's worms eat a strictly vegan diet, eschewing fats, meats, dairy and spices - and they're not mad about onions or orange peels either.
Yet I suppose that's what you can expect when you take a creature out of its natural (and naturally-balancing) habitat and stick it in a bin. If you're running a worm-powered factory, you need to pay more attention to the workers' conditions and rights.
The earthworm (Lumbricus terrestris), which is first cousin to the brandling, is a remarkably hardworking and hardy individual. Thus far it hasn't been enslaved within a wormery, but its ploughing prowess in the open ground is mighty. Every day it eats (and excretes) about a third of its body weight in soil. Stewart reminds us that Charles Darwin - who was keen on earthworms and wrote extensively about them - figured that a healthy earthworm population can shift about 20 tons of soil per acre annually.
They have another notable ability, first brought to notice by Rachel Carson in her book on pesticide use, Silent Spring, published in 1962. Earthworms can absorb large concentrations of DDT, and still survive - making them a deadly meal for the birds that eat them. They can also take up other toxins, a capability that has been exploited by scientists, who use them as "biomonitors" on polluted sites, to gauge what chemicals are present in the soil.
In recent years, worms have displayed a further faculty: they are able to break down harmful PCBs in soil. The Oxford scientist conducting the PCB trials, Dr Andrew Singer, discovered that the worms were also cleaning up methane, one of the greenhouse gases that contributes to global warming. The multi-talented earthworm may not only be the monitor and janitor of our toxic wastes, it may also save the world.
But not, unfortunately, in the forests of Minnesota, where European earthworms are wreaking havoc. Their voracious appetites and ability to till organic matter into the soil (factors which make them such an asset to gardeners) have changed the make-up of the forest floor. If present in large numbers, they can consume the entire leaf-fall of a forest in a single season, so there is no natural build-up of "duff" a spongy layer composed of leaf litter and other organic matter.
Woodland ferns and wildflowers need the conditions supplied by the duff for their germination and subsequent survival. So, no duff - no native plants in the forest understorey. In parts of some forests in Minnesota there is a loss of 80 to 90 per cent of the woodland plants. But how did the alien worms (present in American gardens and agriculture for over a century) arrive into forests in such drastic, ecosystem-changing numbers - seeing as they travel only a few metres a year? Their rapid spread into the uncultivated forests, says Stewart, has been mainly due to fishermen dumping their unused bait in the woods.
As a gardener, I love earthworms, but I have not yet tried stroking one, as Amy Stewart has, after she read about "mesmerising worms" in an old textbook. The worm, she says, seemed to be comfortable with her unhurried, gentle pressure, making no effort to get away.
A slithery thing with which I do have lots of contact in the garden is the snail - although not in a friendly manner. The snail (along with its fellow gastropod, the slug) is my garden bête noire. Not so for British organic gardener, Bob Flowerdew, who in his new book, The Gourmet Gardener, introduces the idea of the "snailery".
A snailery, he claims, is similar to a wormery: a way of converting small amounts of organic waste into plant food. "Confine snails in a moated container - a container set within a tray filled with water - so they cannot escape," he instructs. "Give them some old pots and pipes to live in, feed them green wastes, and wash their droppings out of the bottom of the container; then use these as a liquid feed or blended with top-dressing mixtures."
Does anyone else feel a little queasy? Bob Flowerdew usually gets my vote for "most resourceful organic gardener", but not this time. Flowerdew prides himself on using "wit and cunning" in getting nature to work for the gardener. But his snailery seems to be a schoolboyish contraption, designed more to cause a stir than to be truly useful. On the other hand, I could be wrong, the snailery may be the wormery of the future.