Earthworms: The Mulching Assistant

Earthworms are the ultimate mulch specialists. The common nightcrawler, lumbricus terrestris, is a seasoned mulch hunter. Following every rain, or in the cool, moist mornings, hundreds of earthworms come to the surface to feed.

These “mulch munchers” grab leaves, blades of grass and other bits of organic matter and “tow” them back to their burrows. Deep under the soil, these worms store organic matter, excrete digestive juices to help them decompose the matter and feast upon the resultant compost at a later date.

The worm devours the decomposed mulch and deposits the humus both in the burrow and on the surface as earthworm castings. Since the worms continually excavate and turn the soil, the humus layer remains near the root zone while the surface is continually cleared of debris.

Earthworms will maintain a population level equal to the available feed or mulch. They keep the soil loose, aerated and well drained. Working in harmony with other organisms, earthworms turn under the seasonal mulch layers, “vermicompost” it and convert it to available plant nutrients.

Many gardeners have had success introducing redworms such as eisenia fetida (the common red or “brandling” worm) or lumbricus rubellus (the red wriggler or so-called “hybrid” redworm) to their lawns and gardens. Redworms devour the humus layer of the soil voraciously, quickly turning mulch into castings.

Native to temperate river deltas, redworms require a moist, well drained, rich topsoil with plenty of mulch and organic matter. They will not burrow to escape the frost and drought, however, as do their nightcrawler cousins.

They will only live for a few months in the lawn or garden in most climates. Redworms may have to be replenished annually in the humus-enriched or mulched garden and lawn.

Always remember that redworms cannot make a poor soil good, only a good soil better. The aeration and mulching benefits provided by redworms is hundreds of times that of the less active nightcrawler.

A few dozen redworms purchased at the bait store or a few thousand ordered through the mail from garden catalogs are often sufficient to get started. They breed like crazy and will quickly increase their population to handle any volume of household organics.

Many people add redworms to their compost pile and let them quickly eat the table scraps and other organics stirred into the top layer. Redworms will enable the pile to decompose much more quickly than letting it sit passively.

The best thing about earthworms is that they do the mixing and aerating all by themselves, living on the decomposing compost and the regular addition of discarded fruits and vegetables. You don’t have to turn the pile to get it to cure when you let redworms do the work for you.

But redworms should not be used if you are making active batches of compost. The heat will cook them or drive them to the edge of the pile, often to their death. If using active composting techniques, wait until the pile has cooled before adding redworms.

Many people use redworms year-round right inside the house to take care of their table scraps and a limited amount of shredded paper products. In the basement or under the sink, they keep them in plastic bins that are less than one cubic foot in size.

As long as they are kept warm, moist and protected from light, one small worm bin per person will consume the daily production of vegetable and fruit discards along with the coffee grounds, filter and all, on a year-round basis.

Worm farmers need to periodically remove the rich earthworm digested compost, called “worm castings,” as worms do not like living in their own manure for more than a few months. Worm castings, however, are worth the effort of indoor worm ranching.

This “super compost” is the best ingredient in potting soils and is valued above all other compost products. Experienced gardeners will point to the soil worms in the garden and the redworms in the worm bins as the secret to their exceptional yields.

© 2000, Jim McNelly