Improve Garden Soil with Earthworms

Earthworms benefit garden soil and plants in several aspects: They convert organic material into nutrients that plants can absorb; they loosen the soil, which makes it easier for the roots to grow and the air and water to circulate in the soil; they increase the soil's water retention capability; they bring the mineral and other nutrients that are located deep in the soil to the top layer, where they can be absorbed by the plants.

In addition to their value to plants, earthworms are a major source of food for songbirds in early spring before the seeds and berries are ripened. Earthworms can stay alive for up to 2 weeks if kept in a dark container filled with moist peat moss.

There are more than a thousand species of earthworms. Depending on the species and the geographic location, earthworms have been called night crawlers, field worms, red wigglers, red worms, red hybrid, and rainworms. Any garden is likely to contain more than one species.

Earthworms vary in color and size. They may be reddish, maroon, dark gray, or black. Most earthworms are 2 to 10 inches long, but some species in Australia can reach up to 12 feet in length! They thrive in moist soil that is rich in organic material. They eat partially decomposed animals and insects. Lettuce is one of their favorite vegetables. They also love watermelon rind. All earthworms thrive on manure.

Earthworm feeding habits differ, depending on the species. The night crawlers do not feed on the surface but come to the surface after dusk to collect food, which consists of small pieces of organic matter or grass blades. Using their mouth, they drag what they collect into their burrow where they eat it mixed with soil. Other species including the red wigglers feed on the surface. Earthworms don't eat highly acidic or highly alkaline food.

To provide earthworms with food, organic material should be added continuously to the soil. If the organic material is depleted, the earthworms either leave the garden or die. When they die, their bodies' protein decomposes into nitrogen that is added to the soil. This benefits the plants for a short period of time but doesn't compensate the soil for the loss caused by the earthworms' death.

The food the earthworms eat goes to their gizzard, where it is ground. The ground food moves to the intestine, where it is digested by the worms' enzymes. The worms use some of the nutrients in the food to grow and to fuel their activity; the rest is discharged in the form of granular cast that is rich in soluble nutrients. Earthworms' casting contains 5 times more soluble nitrogen, 7 times more phosphorous, 3 times more magnesium, and 1.5 times more calcium than was contained in the food the worms eat.

During winter, earthworms are inactive. In areas where the soil freezes, they move below the frost line. Frost kills the worms in less than 2 minutes. In spring, when the temperature is moderate and the rainfall is plentiful, they reach the peak of their activity. They mate and lay eggs. Many eggs hatch and the small worms grow and mature. A pair of mature earthworms may produce a few hundred offspring in a year. During summer, the worm's activity diminishes. The food available is not enough for all the worms. As a result, many of them die.

The worms' survival is also affected by the amount of moisture in the soil. If the soil is always moist, the earthworms' chances of survival increases; if the soil dries, many die. In the fall the earthworms' activity increases. They lay more eggs and stay active until winter arrives and the cycle is repeated.

Some species can live for up to 10 years. However, earthworms face numerous dangers including being eaten by birds and moles, lack of food, adverse weather conditions, and the increasing use of pesticides. As a result, some earthworms live for only a few months.