Dr. Curtis E. Swift

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November 8, 2012
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SWIFT: Do you have bumps in your lawn?

Earthworms or are they night crawlers?

No matter what you call them they are a real pain in my lawn. They should be tagged as invasive species. They are not native to our area so why aren't they listed on Colorado's obnoxious animal list.

They have a list for invasive noxious weeds and spend gobs of money trying to control them so why not worms. They cause bumps in my lawn large enough to trip over and break an ankle. Come spring I'm going to have to come up with a way to get rid of them. I have applied compost over my lawn to even out the bumps they create but that just increases their baby worm-producing activities. I hope when spring arrives I don't do anything illegal to control these pests.

Researchers have identified many genes in worms common to humans. They have even replaced worm genes with human genes and discovered the worms did just fine. I wonder if you would have the same results if you replaced human genes with worm genes? Gene replacement after all is not uncommon. Researchers recently created a human embryo combining the genes of two women and one man leaving out the defective genes to prevent babies from inheriting certain rare incurable diseases. That is neat, but now back to earthworms.

Earthworms came over to this side of the ocean along with pigs, cattle, horses, plants, and other species as part of the Columbian Exchange. Worms most likely arrived on our shores in pots of plants brought along by the Puritans and other groups and were carried in the dirt on the soles of boots and in planting material crossing the nation.

Worms were not here prior to Columbus thanks to the glaciers scrapping away any topsoil in which worms might have existed. Without worms, plant debris accumulating around our plants was broken down by soil microbes and the indigenous people did perfectly well without this voracious feeder and we don't need them.

The night crawler, our largest earthworm reaching 8 to 10 inches in length, is often said to be beneficial because it mixes organic matter with soil. Unlike some species of earthworms, the night crawler does little or no soil mixing.

This species does, however, help aerate the soil and eats the thatch in my lawn and the other plant debris on the soil surface. That is the problem. When night crawlers consume the leaves and other plant debris in our lawns and forests, the seeds and plants that require this duff to germinate and take root in can't survive. They also cause bumps in my lawn.

Earthworms speed up nutrient cycling by consuming plant debris. This releases nutrients so quickly that they leach out of the top soil and are no longer available for plant growth. This is a real problem in our northern forests where accumulating plant debris is critical to plant diversity and survival. Without earthworms, nutrients in plant debris would be released much slower and be a greater benefit to our lawns and gardens. Some of our northern forests have changed so drastically due to the earthworm invasion that some plant species are dying off. They need the surface duff to survive. The duff also helps prevent erosion by muffling the effect of rains.

After the last ice age, the northern areas of the country were quickly reforested without the help of worms. When worms decompose the leaf layer, there is a shift in the ecosystem resulting in certain species of trees, ferns and wildflowers being able to survive. This change also affects insects, amphibians, and other members of the ecosystem that evolved without worms. So why do people want to add worms to their gardens, especially organic gardeners? They most likely don't understand the problems these worms cause.

There are a couple of flatworms known to feed on night crawlers. In some parts of the world they have done such a great job, earthworms are now considered endangered. That sounds great to me. I wonder if I can smuggle some in and let them have a go at the night crawlers causing the lumps In my lawn. Hmmm!? I wonder if Dan Bean at the Insectary in Palisade can assist with that introduction. After all he did a great job introducing the salt cedar leaf beetle into our area.

 

Dr. Curtis E. Swift is a retired horticulture agent with the CSU Extension. Reach him at Curtis.Swift@alumni.colostate.edu or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender. For a consultation, call 970-778-7866.


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The Post Independent Updated Nov 8, 2012 02:51PM Published Nov 8, 2012 02:50PM Copyright 2012 The Post Independent. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.