Earthworm, public domain from Wikimedia by S. Shepherd
Besides myriad microscopic plants and animals in each cubic foot of healthy soil, there are lots of macroorganisms, the ones we can see, such as spiders, centipedes, millipedes, springtails, and other insects and critters. But the most fascinating and helpful one is the earthworm. Earthworms inhabit the cool, moist soil in your garden and have a much more important role than that of fishing bait. They are good friends because they provide nutrients, improve the structure of the soil, and benefit other beneficial soil life. There are many species of earthworms, ranging in size, color, soil preference, and life expectancy, but they are all beneficial. Terrestrial earthworms are not insects, they are in the phylum Annelida, or called Annelids.
These "Intestines of the Soil," as Aristotle called them, break up soil hardpans, drill miles of burrows that soak up fast-falling rains, help plants root more deeply into the soil, shift chemically unbalanced soils toward a neutral pH, help make soil nutrients available, and loosen compaction.
A single earthworm deposits its weight in castings every twenty-four hours. That may not seem like a lot, but earthworms in an acre of soil are able to produce about fifteen tons of castings in one year. The earthworms also help increase soil microorganisms while they destroy the harmful fungi, bacteria, and root nematodes as they digest them. The earthworm's digestive system also helps neutralize the soil if it is either too acidic or too alkaline. Charles Darwin, who discovered the great importance of earthworms, stated that vegetation in many parts of the world would be eliminated without the helpful benefits of the earthworm.
Earthworms are attracted to soils that are high in organic matter and free from pesticides and harsh synthetic fertilizers. Earthworms can be purchased from growers or grown at home in moist compost. In order to confine them to a particular area while you are "raising" them, feed them periodically with cornmeal and molasses. This will prevent them from leaving the compost "nursery" until you are ready to introduce them to your garden or landscaped area. Growing your own earthworms or adding them to your garden can be enjoyable, but they will return naturally and increase in population rapidly if you stop using synthetic chemicals and go organic!
What we organic gardeners should be most concerned about is the level of life in the soil. The best soil test is called the earthworm test. Dig a 12-inch by 12-inch by 6-inch-deep section of soil out of the ground and slowly sift it into a box, bucket, or wheelbarrow. Count the earthworms you see in this half cubic foot of soil. If your test is in turf, there should be at least six earthworms. If the test is in a mulched-bed area, you should see about ten earthworms. They should be big earthworms—about the size of your little finger. If your test doesn't uncover enough worms or if they are puny little worms, your soil needs more improvement.
The presence of lots of big plump earthworms shows that nature has been at work and has filled the soil with life. If you see lots of worms, you can rest assured that the beneficial microbes are there too. If the soil is full of life, the chemistry can't be too far from balanced. If the earthworms are present, the soil will be well aerated and aggregated. Earthworm-rich soil will drain better and also hold just the right amount of water significantly longer. Wait until you see the improved plant growth. The bottom line will be improved soil health, greater biodiversity, and greater plant production.
QUESTION: During hard rains, earthworms slither into my swimming pool and commit suicide. I have to use a skimmer to scoop them out of the pool. I’ve tried poking holes in the soil so the rain will soak in better, and I've called a pest-control company. The hole poking didn't work, and the pest-control company says it has no pesticide to kill earthworms. How can I get rid of these nasty creatures? — F.S., Dallas
ANSWER: First, earthworms aren’t "nasty creatures." They are one of the most beneficial organisms on Earth. Plants grow better in the presence of earthworms because the worms loosen and aerate the soil with their movements and fertilize it with their waste, or castings.
And these are just a few of the benefits.
People have wondered for years why earthworms appear to commit suicide by crawling onto pavement or into swimming pools. I think the best theory is that vibrations disturb the worms. The mass suicides related to rain probably are caused by the vibrations of thunder and lightning, and there probably is no way to stop this behavior. Some gardeners have reported similar experiences where diesel engines and pumps are running.
Are earthworms native to North Amercia? Yes. From The Smithsonian
Note: Not all earthworms are equally beneficial. This report from Oregon of "High Jumping Worms" tells of introduced worms that could out compete native species.
Search Library Topics Search Newspaper Columns