Little-Known Facts About Earthworms

With some little-known facts about earthworms, gain a greater understanding of one of the unsung heroes of the vegetable garden.

Clitellum of Earthworm

On this earthworm, you can clearly see the clitellum, the swollen band about one-third of the way from the worm’s head.

iStockphoto.com/Franz Schlögl

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Little boys love to dangle them before little girls. Fishermen covet them, and chickens relish them. If you’re a gardener, they can be your best friend, aerating the soil, consuming and digesting vegetation and organic matter, and improving soil fertility with their castings. They’re earthworms, and the more you have, the better off you are. Keep reading for some little-known facts about earthworms, one of the vegetable garden's unsung heroes.

About 180 types of earthworms are found in the United States and Canada, most of them the descendents of worms that were inadvertently brought to North America from Europe in the rootstocks of plants or in ships’ ballast. Over the last two centuries, they’ve populated nearly every corner of the continent. There’s no way of knowing just how many there are in America, but some scientists estimate that rich, fertile farmland may contain as many as a million or more earthworms per acre, and that even an acre of poor soil can support as many as 250,000 of the wrigglers.

The fat worms you find in your garden are likely night crawlers that burrow into the soil and spend most of their lives underground. The tunnels they create allow air and moisture to pass readily through the soil, and the tunnels can retain water that garden plants can take up as needed. Worms eat organic matter, including decaying leaves, bacteria, and decomposed animal and insect remains. In return, they enrich the soil with their excrement, or castings, which are rich in concentrated nitrate, phosphorus, magnesium, potassium and calcium. They also produce 60 percent of their body weight daily in urine, which contains high levels of beneficial nitrogen.

Why do earthworms come to the surface after a rainstorm? Not to avoid drowning, as myth suggests, but because the temporarily wet conditions make it easier for them to relocate from point A to point B without dehydrating or baking in the sun. They also crawl to the surface to retrieve bits of leaves and organic matter that they pull into their burrows. Earthworms also frequently crawl to the surface in wet weather to mate.

A worm’s body is essentially a tube containing a mouth, reproductive organs, and a digestive system. Worms don’t have eyes or ears or lungs, but breathe through their skin. Lacking bones, worms rely on a complex system of muscles and tiny, nearly invisible bristles to pull and push themselves forward. While worms are hermaphrodites, and have both male and female reproductive organs, researchers say it still takes two to tango. Most garden variety earthworms live one to two years, although their lifespan can reach four to eight years under field conditions.

Does the early bird really get the worm? Actually, yes. In fact, several species of birds prey on earthworms, including starlings, thrushes, gulls, crows and robins. When you see robins hopping around on your lawn after a rain shower, they’re simply waiting for the buffet to be served. And since an earthworm’s body is composed of nearly 70 percent protein, they are also a favorite snack for many species of snakes; mammals, such as bears, foxes and moles; and invertebrates including beetles, snails and slugs. And if you’ve ever used a fat night crawler to catch a bass or crappie, you know that earthworms make great fishing bait.

Red worms or red wigglers are the worms most often recommended for vermicomposting – composting that uses worms to do all the heavy lifting. Unlike earthworms, red wigglers live and feed near the surface of the soil, eating organic matter that is beginning to decompose. Red wigglers will eat kitchen vegetable scraps, leaves, coffee grounds, yard clippings, even paper and natural-fiber cloth, producing half their weight in castings daily. Vermiculturists claim a pound of red worms (750 to 1,000 adult worms) can eat their way through a half-pound of food scraps each day.

Adult red worms are extremely prolific, producing two to five egg capsules per week, with each capsule producing two or three hatchlings. It takes about 45 days for the eggs to hatch, and about six weeks for the hatchlings to become breeders. If, say, you purchase 1,000 red worms for your compost pile, your worm population could more than double in a matter of weeks.

Red worms generally grow to 3 or 4 inches long, while night crawlers can reach 8 to 10 inches. The biggest known earthworm is the South African Giant Earthworm, which can reportedly reach a length of 22 feet. Here in the United States, a rare species called the Giant Palouse, which can grow up to 2 feet in length, has occasionally been found in eastern Washington state.

Finally, is it true that a worm can survive if you accidentally cut it in half? The experts say that the front half of an earthworm can regenerate its back half if the front part is long enough to contain the clitellum (the swollen band about one-third of the way from the worm’s head) and includes at least 10 segments behind it. Now that’s an impressive feat!   

Jerry Schleicher keeps an eye open for night crawlers to bait his hook when he goes fishing in Parkville, Missouri.