Composting 201

"Interesting Facts About Earthworms"

One of the best reasons for composting and spreading the finished product is that you are providing a perfect food for earthworms.

The benefits of earthworms are well-known. They are tireless tillers of our soils and their castings are the richest and best of all fertilizers. It is would be impossible to ever have too many in our gardens, unless you don't want lush, healthy plants!

Earthworms need moist soil to survive. Our dry North Texas summers are lethal to many, especially those that happen to end up in the lawn areas that receive full exposure to the merciless summertime sun. It is no wonder that people have so many problems with their lawns - they are inhospitable to the creatures that do the most to benefit the soil, and without healthy soil you won't have healthy plants.

During periods of drought, the earthworms recede deeply into their burrows, which can be six feet deep. The mucous from their exterior helps to provide structure to their burrows so that they do not collapse.

Rototilling the soil can be harmful to earthworms. Not so much from the machine, as they flee from vibration, but mostly because their food supply is depleted rapidly when exposed to oxygen. If you rototill, you should immediately cover the area with partially finished compost or waterlogged leaves.

The most common garden earthworm, the nightcrawler (lumbricus terristris) is not native to North America and was in fact brought,over in potted plants by Europeans. Most of the native North American earthworms were killed during the last Ice Age 10 to 15 thousand years ago. This is one case of where the accidental introduction of a foreign species has been beneficial.

Garden earthworms are not to be confused with composting worms that can be kept in containers. L. terristris is a burrower, and will kill itself trying to burrow in a worm bin. Composting worms cannot tolerate temperature extremes, and though they can survive inside a compost pile, will perish if left to their own in garden soil.  (Personally, I think that the compost worm gets more attention that it deserves relative to L. terristris, at least here in suburbia, where food waste volume is small relative to yard waste volume. Densely populated cities and apartment complexes are more appropriate for indoor worm bins.)

Worms are hermaphroditic, meaning that they possess both sets of sex organs. However, they still need to mate with another worm in order to produce offspring. The raised band that encircles the worm is actually a carrying case for its eggs. Once the eggs are formed, the band migrates along the worm's body and it is then shed and the eggs left to hatch.

A few more facts about our subterranean allies...

Earthworms:

- have been kept alive for 6 years, but in the wild probably live two years at the most;
- do not have lungs, breathe through their skin, and can live under water for a while;
- do not come to the surface during rain to escape drowning, but rather to find a mate since their mobility is much better on wet ground;
- lack eyes but are light sensitive;
- can detect the motion of a robin (that can hear the earthworm in its burrow);
- may survive being frozen if the freeze is not too rapid

If you want to learn more about earthworms, the references below are excellent sources (especially the third one - it is enormous!). Amazon.com has books on earthworms, but nothing that looked good enough to buy.

Maintaining a healthy population of worms is easy. Just use common sense and see that they have a moist, well-mulched habitat with plenty of decaying matter. Take care when turning the compost pile. A pile interior might contain dozens of worms, so try to relocate them to an area where they will have a good chance in which to burrow deeply. Worms are resilient, have a high reproduction rate, and can survive without us. But with just a little help they can be made to flourish. And you can forget about ever needing a rototiller.

References:
1. "Earthworms", by John Mertus, 1993:
http://www.mertus.org/gardening/worms.html
2. Encyclopedia Britannica Online:
http://www.britannica.com/bcom/eb/article/8/0,5716,32278+1,00.html
3. The Southern Crop Protection and Food Research Centre (Canada) Earthworm FAQ: http://res.agr.ca/lond/pmrc/faq/earthwor.html