Why dig the garden, when the worms can do it for you, asks Jane Powers.
'Now is the time to dig your vegetable beds. Leave the soil in rough clods and the exposure to frost, wind and rain will break them up." No! You won't be finding that advice in this column, although it has been received gardening wisdom for over a century.
Imagine for a minute that you, your family, your neighbours, the postman, the man who reads the ESB metres, and the other people who happen to be passing down your road are going about everyone's daily business. Then along comes a great big spade, crashing into your world, slicing through the roof of your house. The postman, carried in with the spade, hurtles across your breakfast table, hits the goldfish bowl, and before you have time to think, you, the postman and the goldfish are shovelled onto the remains of your street. Then, imagine being left in this helpless state over winter, in the frost, the wind and the rain. It would be some time, I think, before it was business as usual again.
And that, if you'll pardon the extreme metaphor, is why I won't be digging my vegetable beds. The soil, you see, is heaving with life: earthworms, woodlice, beetles, springtails, fungi, bacteria and other near-invisible micro-organisms. All these interdependent life forms (the "microherd", as a fellow organic gardener calls them) make the soil a congenial place for plants to live. Dig into the ground and you mess up the microherd, by destroying them and their highly-organised habitat.
Earthworms are the most obvious do-gooders, hauling organic matter down into the soil and opening its structure with their tunnels. Air, water and plant roots travel easily along these channels. The castings (the finely-textured droppings) left behind by the soil burrowers help to nourish plants. Sir Albert Howard, one of the many champions of the heroic earthworm, wrote in 1945 upon his observations of potato roots: "Whenever they passed the earthworm casts, a fine network of roots was given off laterally which penetrated the casts in all directions".
Beetles, springtails and woodlice are other primary processors of organic matter, chewing it up and excreting it into the soil. There it becomes humus - the magical material that is both plant food and soil conditioner (the latter improves soil structure by aiding drainage in heavy clay and water retention in light soil).
The smallest members of the microherd, the bacteria, help produce humus, but they also have other, specialised jobs. Some fix nitrogen from the air, others break down phosphorus in the soil and make it available to plants, still others attack harmful pathogens.
But perhaps the most remarkable of the subterranean dwellers are the mycorrhizal fungi. (Yes, I know, fungi sound even more dreary than bacteria, but they are crucial to a happy soil.) Mycorrhizal fungi live in and around the roots of plants, feeding on sugars and other nutrients passed through the roots.
In turn, the fungi, whose tubes are more efficient than root hairs at absorbing nutrients and moisture, help to feed and water the plant. A plant that is enveloped in a thriving mycorrhizal colony is less likely to suffer from heat, drought and disease.
This cosy underworld - where the microherd grazes contentedly among the filaments of fungi - is well-organised, but fragile. Organisms die if they dry out, or if they are suddenly exposed to cold or heat. The last thing you should do is wallop into the soil with a great clumsy spade. Which is why I have not dug my vegetable beds in three years. Instead I pile on an inch or two of garden compost, and let the worms plough it into the soil. They dig. I don't.
Another gardener who lets the worms do the work is Jean Perry, whose garden at the Glebe, in Baltimore, west Cork (pictured on these pages), produces some of the healthiest vegetables and cut flowers you'll ever see. Her regime for her kitchen beds includes deep mulching, "six or nine inches", she advises. "If you can do it before there's frost, you can keep the beds warm. The mulch stops frost penetrating and prevents the rain from washing away nutrients."
Jean covers her soil with a layer of garden compost, then seaweed, and tops it off with a thick blanket of straw. In spring, she simply pulls aside the mulch and plants through it into the soil. In time, the whole lot disappears underground, thanks to the activity of the busy worms.
The soil at the Glebe is light, as is mine, which makes it easy for earthworms to till. But what about heavy clay? Is there a worm muscular enough to tunnel through this difficult substance? Well, yes there is, in Balbriggan, where Kathryn Marsh gardens on "very, very, very sticky, cold blue clay ... There was a brick factory in this lane for 300 years."
Kathryn's vegetable beds, having been mulched assiduously for years, now have a foot or more of good black soil, worked entirely by worms. Indeed, she has found that when she digs in organic material herself, it does not meld as well as when the worms do the chore for her. "The soil gradually turns from blue to yellowish over many years, but stays sticky and impossible, and I have to use a digging fork to weed it."
To have a successful no-dig garden, it's not enough to simply hang up the spade. The surface of the soil must be covered in a mulch. Some mulching materials are rich in carbon: newspaper, leaves and straw. Others are nitrogen-rich: grass cuttings, soft herbaceous clippings, and farmyard manure. Carbon-rich and nitrogen-heavy substances should be layered so that they provide a balanced diet when they break down.
After some months, the mulch is pulled underground by our friends, the worms, where it eventually feeds our plants (and the benevolent microherd). But in the interim it protects the soil surface, insulates it and keeps down weeds. When it disappears, it's time to layer it on again. Nature, you will notice, never leaves her soil bare, except in deserts, dunes and other extreme habitats.
So, fellow gardeners, now is the not the time to dig. Now is the time to swaddle and coddle your soil.