Earthworms...The Canaries Of Your Landscape

Weatherproofing Your Landscape is all about the health and weather-tolerance of your trees and shrubs. So you might be wondering: What do earthworms have to do with that? Well, it happens that these little squiggly creatures have a lot to do with your big anchor plants.

For one thing, earthworms are the canaries of your landscape. If you dig a hole a cubic foot deep and don't find at least 5 plump and lively earthworms, you can bet that your soil lacks the organic matter and microbial action necessary for healthy plant growth—be it pansies or a mighty oak tree.

Here's the scoop on why you should care:

Earthworm castings (poop) have a nitrogen-phosphorus-potassium (NPK) rating of 5-5-3. Castings sell for up to 25 bucks a pound. For every three earthworms, your soil gains around a pound of this high-grade organic fertilizer each year. Worm-friendly soil can host up to 25 earthworms per cubic foot. Do the math.

As if that weren't reward enough for treating these guys with royal respect, earthworms help neutralize soil pH by oozing calcium carbonate. (I guess you could say they're the Rolaids of the garden.) And their miles and miles of tiny burrows allow air, moisture, surface nutrients and roots to penetrate deeply into the soil. They also treat lawn thatch and harmful nematodes like Thanksgiving dinner.

Ya just gotta love 'em.

So here are some things you need to know about your little subterranean buddies.

• Earthworms have the sunlight tolerance of Dracula, coming out only at night to grope for food. (They collect on the surface and haul everything downstairs.)

• They like soil temperatures of 50F to 60F degrees. In the heat of a summer day or during winter, they burrow deeper to find that temperature.

• Move a worm to unfavorable soil, and it'll die, pronto.

• Earthworms have a taste for grass clippings and shredded leaves, as well as banana peels, coffee grounds, composted cow or rabbit manure, and ground eggshells. (Steer clear of pickled foods and salt.)

• When adding a powdery substance to the soil, suspend it in water first, or it'll desiccate worms.

• Even if you don't have earthworms, you probably have them. Worm eggs can remain dormant for long periods...until you create a favorable habitat for them.

• With earthworms, you don't need to till. In time, they will burrow up to 6 feet deep, turning the soil as they go.

• Earthworms breathe through their skin, so any chemicals used in the landscape will either repel them or kill them outright.

The best earthworm habitat I've ever seen was beneath a bird feeder outside my living room window. Over a period of months, birds left a layer of sunflower-seed hulls several inches deep. I could rake my fingers through the moist hulls and stir up masses of huge, fat, wriggly earthworms.

If only the robins had known...