Nightcrawlers: The Natural Fertilizer

Lately we have had some calls from concerned people who want to get rid of the night crawler population in their lawns. So we have put together this handout to give you all the information, please read this before you decide whether or not these worms have to go.

A night crawler is a type of earthworm, which besides its popular uses in fishing, is also great for your lawn. The fact that you have nightcrawlers in your lawn is an indication that your lawn is healthy, because their presence is incredibly beneficial. They are constantly digging little tunnels through the dirt, which allow air and moisture to reach the roots of your plants. They do a great job of aerating the soil. These worms feed on not only the dirt in your lawn, but also the thatch, which is the mat of living and dead plant material that builds up along the soil surface. Too much thatch interferes with the oxygen and moisture absorption of your lawn, and can lead to weak roots. These worms produce a fertilizer that is incredibly rich and good for the soil. It is full of nitrogen, phosphorus, potassium, and other beneficial nutrients, as well as lots of important beneficial bacteria. The fertilizer these worms produce is so nutritious that it is even sold in stores!

Some people do not want nightcrawlers in their lawn because they create small lumps of dirt at the soil surface. These lumps are called castings, and they are actually made up of the fertilizer that the worms produce. These castings can leave the lawn bumpy and unpleasant to walk on. One easy way to solve this is to simply rake the castings into the lawn regularly. This allows your lawn to benefit from their nutrients. Do not press these castings into the ground, as this will cause soil compaction. You can also minimize the number of castings by watering your lawn deeply and infrequently, allowing the top inch of your lawn to dry out between watering. This encourages the worms to stay below the surface, as well as encouraging your grass to form deeper root systems.

If you have tried these methods, and you still are not happy with the nightcrawlers living in your lawn, you can use a chemical pesticide. There are no pesticides labeled for use on nightcrawlers, because they are not ordinarily considered a pest, but a desired addition to the lawn. The chemical insecticide Diazinon will effectively kill these worms, but remember this is a poison and may have negative impact on other beneficial organisms like birds.

Written by Dr. Bill Paton and Laura Tilley