Firstly, the term earthworm is just a common name that encompasses any of the legless, tube-shaped, segmented worms that live in soil. This term therefore includes many different species and means that they can range from tiny inch worms to rather large nightcrawlers growing up to 35 cms. So, are they a problem for your lawn?
Actually, the presence of earthworms in the soil below your lawn is an indicator of healthy soil that contains a high level of organic matter. In most cases, there is no reason to worry about worms in your soil. In fact, it’s more of a concern if your soil has no worms in it since this indicate a fairly sterile soil which lacks organic material.
Typically, worms are entirely unseen. They just go about their business, conditioning the soil deep in the root zone. During time of extreme moisture though earthworms tend to migrate to the surface and leave casting on the lawn. Castings are small bumps or mounds on the lawn. They are basically worm excrement but are highly nutritious for your lawn. These castings are nutrient packed remains of digested plant matter and soil that has passed through the earthworms.
Earthworms also assist in breaking down thatch (the spongy layer of turf), increasing decomposition and creating usable nitrogen in the soil. 5 or more earthworms per 30 cms square of soil provides your lawn with around 25% of its seasonal nitrogen requirements.
And, as the earthworms move through the soil profile, they act as a natural aeration system, helping water and air move from the surface through to the root zone.
Overall, the only reason earthworms may be viewed as a problem for lawns is if you are looking for a perfect lawn and find the worm castings left on the surface offensive. Castings can, over time and if in extremely large numbers, create a bumpy surface causing scalping when mowed or even a trip hazard. If this is happening on your lawn castings can easily be dealt with.
- Rake or sweep castings across the lawn when they are dry. This has the effect of spreading a natural fertiliser over the turf and breaking apart the unsightly lumps.
- Don’t overwater. Earthworms will stay near the surface if it’s continuously moist, but they will go down deeper in search of moisture if the top few cms of soil are drier.
- Mow high and keep the lawn healthy to hide the castings and minimise the unsightliness.
- A roller can be used to press down the castings; but over time, bumpiness will still occur and it can cause compaction of the soil.
Lawns made uneven and bumpy due to years of casting build-up may need restoration or renovation depending on the severity. Topdressing and re-turfing will take care of moderately bumpy turf. In more severe cases, aerating and rolling may be necessary to achieve smoothness.
If you are in need of new turf just contact the team at Daleys Turf today.