I am often asked, "Will earthworms hurt my grass?"
A client (and friend) of mine sent me an email after she took her puppies out for a late-night potty break. She was shocked to discover worms crawling all about the lawn. She asked me if it was normal to see 100's of worms in the grass? I get asked this question often. So, I thought I would share my response...
It can be shocking the first time you notice it. But not only is a large quantity of earthworms desirable, it is awesome! Earthworms are an indication/result of healthy (and non-toxic) soil with an abundance of organic material for them to consume. When worms eat (and eliminate waste), they convert nutrients, that are tied up in the soil and organic matter, into a plant available form to be utilized by the turfgrass.
Earthworms are nature's aerators (superior to mechanical lawn aeration) and nutrient miners. They are exceptionally good for the lawn, soil, and environment. They convert all the organic goodies that we apply, into plant available forms. A high earthworm population in your lawn is evidence that our holistic fertilizer program is working. Our promotion of a healthy earthworm population is how/why we do not need to apply the high amounts of pesticides most other companies apply while achieving superior results. Without earthworms, my environmentally friendly fertilizers, weed controls and insect controls would not work as well.
Worms spend most of the day several inches below the surface to hide from predators (birds) and protection from heat and sun exposure. As the sun sets, they emerge from the soil to feed and collect food. They eat organic matter and surface litter such as partially decayed leaves, sticks, bark, grass clippings, dead bugs, and other organic waste. They will also surface just ahead of, and during, significant rainfall (to keep from drowning in the saturated soil.
The reason most lawn care companies NEED to apply harsh fungicides and insecticides, as well as perform mechanical core aeration services for their client's lawns, is because they have killed off, or driven out most of the beneficial life in the soil. The soil then becomes anaerobic (lacking oxygen), sterile and compacted. Earthworms, as they burrow and tunnel through the soil, create pathways for roots to follow deep into the lawn where they can reach nutrients and moisture from greater depths. Worms also open the soil to allow essential oxygen to find its way to the root zone of the lawn. This natural process is far superior to (expensive) mechanically core aerating the lawn.
As you can see, earthworms are greatly beneficial and an essential part of a holistic (and organic) lawn care program.