Gardeners usually think of earthworms as their friends. The worms move through the soil, aerating it so that the roots of plants can penetrate more easily and creating a rich medium for growing desirable plants.

The earthworms aren’t native – Nightcrawlers and their relatives came over with the early European colonists and, like the colonists, have made themselves at home – but they are beneficial.

Since 2014 at least, a new type of worms, which go by the name Asian, crazy or jumping worms, has been making its presence felt in Maine; interestingly, evidence of them in Maine greenhouses dates as far back as the 1920s. These worms are degrading not only home gardens but also forests and other wild lands.

The worms get their nicknames because when you pick them up, they wiggle and thrash like crazy, occasionally seeming to jump. Justin Schlawin, an ecologist with the Maine Natural Areas Program of the Department of Agriculture, Conservation and Forestry, said in a telephone interview that the worms are prevalent in the Portland area but have yet to make it much north of Bangor.

Three related species of these worms are in Maine; the most common is Amynthas agrestis. They originally came from China, Korea and possibly Japan, Schlawin said.

What’s the problem with them?

“Amynthas worms degrade soil for perennials,” Schlawin explained. “The ultimate result is that they digest all of the organic matter in the soil, which results in the compacting of the soil and a reduction of carbon, which affects climate change.”

Most perennial flowers, as well as vegetable plants, need that organic matter to grow.

In forests, invasive shrubs are more likely to propagate in areas where the Amynthas worms are established. Garlic mustard, which is on the state’s do-not-sell list of invasive plants, grows only where earthworms are present, but that includes the European worms as well as the newer ones.

An invasive juvenile Crazy worm, found in a woodchip pile at the Topsham transfer station in 2020. Mature Crazy worms have a smooth, milky white band near their head. The worms are bad for your garden and bad for the forests. Photo by Raija Suomela

Amynthas worms (Schlawin uses the term to cover all three species of the jumping worms) are an annual species. Adult worms lay eggs and create cocoons in the fall, and then die. Juvenile worms show up in May and June, and adults are most prevalent in September and October.

Originally, because the worms place the cocoons just a few inches below the ground, it was thought cold climates would halt their spread – but the worms seem to be moving north despite the cold.

Now, for gardening advice.

If you don’t have the Amynthas worms, make sure you don’t bring them in. If bringing compost in to your garden, bagged compost is safest, Schlawin said, although it comes in plastic. If buying in bulk, check to see if the compost was on a slab rather than in a field, which will help prevent worms from hitching a ride with it. The heat of commercial composting should kill the worms and their eggs, he said.

The worms have also traveled with wood chips and mulch, so make sure those products are clean, as well.

Don’t bring in potted garden plants from friends unless the soil is washed off the roots and the plants are replanted in a commercial planting medium. That became the rule when winter moth hit parts of Maine, and it is just as important for the Amynthas worms.

Plants from commercial nurseries are inspected, and should be safe.

In addition, wash soil off of garden equipment, vehicles, boots and tires when you are traveling between sites, although such traveling is more common among professional landscapers. The soil could contain the worms or cocoons, and you could unknowingly transmit them.

If you already have the jumping worms, there are several ways to deal with them, although Schlawin cautions you not to expect to get rid of them. Experts have not yet found any way to eradicate them.

For starters, add organic matter, like compost, to your garden. Ideally, use compost from your own property or your own town – to avoid potentially bringing in even more Amynthas worms from somewhere else. If your neighbor has the worms, you probably do, too.

The compost will replace the organic matter the worms have taken.

Cornell University created a fact sheet on the invasive worms. If you want to find out if your garden is infested, the sheet says, mix a third of a cup of ground yellow mustard seeds into a gallon of water, and slowly pour it onto the surface of the soil. Both European and Asian worms will rise to the surface. You can identify the Asian worms by the raised white band near their heads. Nightcrawlers have a raised pink band nearer the middle of the body.

My wife Nancy and I have yet to see the worms on our property, but I plan on running a test as soon as I find some ground yellow mustard seed.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.