If you do not have enough worms in your garden organic materials are unlikely to break down to a point where your plants can take up the nutrients through their roots. There will be a lack of aeration which encourages fungi and that nasty swamp odor sometimes found in soils down here. Water may be retained longer in clay and not as long as needed in sandy soils with out earth worms mixing things up and breaking things down. A lack of earthworms can also hurt the pH levels in your soil.
There are 2700 different kinds of earthworms known. Worms have five hearts. Worms are covered in a mucus that keeps them moist and allows them to breath through their skin. Worms have been on the planet for 120 million years. That is the time when continents were breaking apart and flying birds and flowers were just beginning to appear. The Egyptians considered earthworms to be sacred.
One acre can contain a from 50,000 earthworms to a million earthworms consuming up to 10 tons of debri and turning up to 40 tons of soil per year.
Not to worry if you spear one with your garden shovel. A worm’s body has up to 100 segments, new segments will grow on the front section. Worms are both male and female and will mate in spring and summer.
There are earthworms near the Equator, Espinals, that grow to 8′ in length. Glaciers wiped out northern North American earthworms and the Europeans brought them back when they moved here. Some northern forests are having problems with earthworm infestations.
Earthworms show up after a rain just because it is easier for them to move about the surface when it is wet. They suffocate when they are dry, not wet as folklore would have us believe.
You can buy earthworms if you need more. I haven’t tried this but who can miss all the ads in the spring catalogs. It is the fastest way to rejuvenate poor soil.
I am a big fan of earthworm castings and buy and distribute a healthy amount throughout the yard twice a year. It is a fantastic fertilizer and castings also attract more worms to your garden.
Once you get a sufficient amount of worms in your garden then nutrients will get broken down into small parts for the plants. Worms beget worms and the population grows. Good microbes multiply. As the worms work the soil they leave air pockets that the good microbes need. The good microbes keep the fungi and other pathogens in check. All of this means less fertilizers are needed and less pesticides. Cheaper and less work for you and better for the environment.