Husker Hort

A Nebraska View of Horticulture

Got (Earth)Worms?

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earthworm castingEveryone wants the dream lawn they can walk on barefoot or push a lawnmower over with ease.  To some, this may sound like a dream.  Rough, bumpy, uneven lawns can be a pain to walk on or to push a mower over.  The cause isn’t a disease or critter, but you might be surprised who the culprit is.

Just as you have been busy this spring, the earthworms have also been busy.  The activity of earthworms often creates a rough and bumpy lawn surface that can be annoying.  The earthworms create burrows and small, hard mounds of ‘dirt’ called castings, also known as earthworm poop.  Castings left on the soil surface by earthworms can cause the lawn surface to be a little to extremely bumpy.  If you have ever driven a lawnmower over the extremely bumpy lawn you know how difficult it can be.

Earthworms are valuable to the overall health of the lawn. Their activity improves the turf by increasing air and water movement in the soil, help decompose organic matter, as well as alleviate compaction. A healthy earthworm population is important for managing thatch and compaction in turfgrass… and let’s not forget that they make great fishing bait.

If you find byproducts of the earthworm activity to be annoying, there are various lawn care practices you can do to help reduce the problem. Bumpiness in sparse, thin lawns will be less noticeable if a healthy thick turf is reestablished through reseeding.  Kentucky bluegrass can be overseeded throughout the month of April at a rate of .75 to 1 pound of seed per 1,000 square feet.  Tall fescue lawns that have been thinned can be overseeded at a rate of 4 to 6 pounds of seed per 1,000 square feet starting April 15 through June 15th.  If renovation of the entire lawn is needed, use the full seeding rate.  Kentucky bluegrass’s full rate is 3 to 4 pounds of seed per 1,000 square feet.  Tall fescue seeding rate is 4 to 6 pounds of seed per 1,000 square feet. Proper fertilization, mowing and irrigation of the site can also help.  Earthworms prefer moist soil.  Make your turf less appealing to earthworms by irrigating less frequently and allowing turf to dry out in-between waterings.

There are some steps you can take to fix the rough patches in the lawn.  Mechanical means may be needed reduce bumpiness and to even out the castings left by the worms.  Core aerifying, power raking, and verticutting are all mechanical processes that will break down some of the bumps in the lawn. Roughness accumulates over several years and it should be gradually removed instead of all at once.  Some of the mechanical means of reducing the roughness in the lawn can even out the terrain of your turf, but they can tear up your turfgrass plants.  Consider doing these methods in the spring or fall when cool season turfgrasses are better able to combat the damage or consider overseeding at the same time to help ensure a full lawn.  Using a heavy roller can cause some longer term issues and isn’t the first choice of a management option. Rolling may remove some roughness, but it also damages the turf by compacting the soil. Compacted soil reduces turfgrass vigor and eventually leads to a thinner lawn.

There are no pesticides labeled for the control of earthworms. Some pesticides and fertilizers are known to have negative impacts on earthworm populations when they are applied for control of other pests.  The active ingredient carbaryl has been shown to have effects on earthworm populations for 1-3 weeks after application.  This also is true for insecticides that have a combination of pyrethroid and neonicotinoids.  A product like Early Bird is a fertilizer that can also have a negative impact on earthworm populations.

Although rough, bumpy lawns aren’t the most ideal situation there are some things that you can do to make your lawn more even, less rough and still embrace the earthworm.  Presence of these little wigglers are a sign of a healthy lawn, even if it is a little bumpy.

Elizabeth Killinger is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at elizabeth.killinger@unl.edu, her blog at https://huskerhort.com/, or HuskerHort on Facebook and Twitter.

Earthworm PDF

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Author: Elizabeth Killinger

A Nebraska Extension Educator out of Hall County with a focus in horticulture and sustainable landscapes.

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