Managing jumping worms looks like the only option

It was just 11 years ago that invasive jumping worms were discovered in Wisconsin. Since then they’ve spread across the state, showing up in large quantities in gardens.

On their own, these worms, which are named for their habit of thrashing around, move slowly, but they’ve spread rapidly with the help of humans. Worms and their eggs are in soil, compost, mulch and potted plants but can also be spread on equipment, tools and even shoes. And since a single worm can start a new colony through asexual reproduction, there’s a good chance the worms are in any garden that has brought in any outside materials, including plants, in the last several years.

The worms are different from other earthworms because they feed voraciously on the top several inches of soil at such a rate they deplete the soil of nutrients, altering the composition and leaving little for plant roots to survive in. They have few predators, possibly because they are very high in heavy metals.

I found jumping worms in my garden several years ago, and based on the location it’s reasonable to assume they came in with bulk soil. And although I’ve noticed some signs of damage, the biggest issue I’ve come across until now was the disgusting experience of finding the worms late in the season when they are large, behave a little like snakes and are usually found in groups.

But this spring, a small corner of the garden has shown the signs of a massive jumping worm infestation. Almost three-quarters of the plants there did not survive the winter, and some that were struggling had almost no roots left. The characteristic “coffee ground” soil, indicative of jumping worm activity, was obvious, and a “mustard pour,” in which ground mustard mixed with water is slowly poured over the soil to test for worms, which are irritated and rise to the surface, yielded an incredible number of juvenile jumping worms.

Although researchers — primarily led by those at the University of Wisconsin-Madison — are working hard to understand and develop management strategies for jumping worms, they have yet come up with much that’s proven to be effective, and it seems clear that eradicating the worms is not possible. Rather, the future seems to be focused on learning to live with them and managing populations to avoid spread to forests and farmland.

So the plan for now is to identify plants that can survive in the depleted soil left behind by worms. Deep-rooted plants or those with thick roots seem to stand the best chance. In my garden that was Amsonia, Jersusalem sage (Phlomis tuberosa), yarrow (Achillea) and sea lavender (Limonium latifolia) and, surprisingly, ornamental oregano (Origanum). Baptisia and other deep-rooted native plants are also likely good options.

As much as gardeners hope for a solution to this invasive species, after more than a decade of living with them in the state it seems that we’ll have to settle for management techniques instead. It’s all part of adapting to the next challenge, something gardeners hold their nose and do all the time.