Trott column: Jumping worms hitch rides at plant swaps
Squiggly invasive worms can kill plants, change soil structure.
It’s the time of year for neighborhood plant sales and swaps. Every gardener loves to share favorites across the fence and sometimes across the state.
If you are looking to purchase or swap plants you need to be on the lookout for jumping worms. Jumping worms are a relatively new arrival in Minnesota, joining a host of other invasive earthworms in our state. Unlike most of our other earthworms, however, jumping worms are causing great heartache for gardeners and significantly changing home gardening practices for those unlucky enough to have discovered these lively and voracious pests.
Most species of earthworms are found throughout the top 6 feet of soil in many of Minnesota’s ecosystems. Jumping worms only live in the top few inches of soil and can be twice as abundant as all the other worms in the area combined. This large volume of worms living in the top-most layer of soil eat many fine root hairs and have been known to kill plants and completely alter the soil structure. For reasons that are unknown, jumping worms also seem to push out other species of worms when they invade a site, their impacts echoing far below their shallow habitat.
Jumping worms eat wood chips and overwinter as eggs in cocoons about the size and color of poppy seeds. These traits make them very easy to move and hard to spot. Jumping worm eggs can be spread in fall leaf management and removal, soil, in plants and via wood chips, including wood chips purchased from big box stores. Sadly, there are no scientifically proven treatments for worms, including jumping worms, so the best management is prevention.
Be a savvy consumer
Don’t accidentally bring home big trouble—ask where the plants were grown. Greenhouses or plant nurseries that use weed-free soil are likely worm- and weed-free. The same treatments that kill weed seeds should kill jumping worm eggs.
Be wary of plants, soil, compost and wood chips that have been sitting on soil, even those bagged and sold. To further frustrate matters, some municipal yard waste and compost sites have reported jumping worms. Compost is a great vector for worms, including jumping worms, so be careful.
Inspect plant swap goodies
Plant sale organizers and participants can play a big role in limiting the spread of invasive jumping worms. Soil, plant roots and mulch are the most likely materials to spread jumping worms during plant sales. Follow these recommendations for safely participating in plant sales:
Confirm that the plants do not come from any areas known to have jumping worms. Additionally, determine that there is no reason, such as soil that looks like coffee grounds, to suspect there are jumping worms at the site that produced the plants.
Remove soil from all plants before transporting them as bare-root plants or potting into sterile potting soil. This helps to remove earthworm cocoons (egg cases) and weed seeds.
View Extension’s full list of guidance on plant sale best practices.
Spread the word about jumping worms
Many people don't know about jumping worms until they find an infestation of their own. In many neighborhoods “free” signs pop up next to hostas, lilies and other common garden plants during the growing season, but these plants or soil may have jumping worm eggs or even tiny worms attached to them. Likewise, farmers market stalls often include plants dug up from their farms. You can help stop the spread by talking to neighbors and plant vendors about jumping worms, and encouraging them to only share bare root plants when possible.
Look for and report jumping worms.
Extension has great information about jumping worm identification and reporting. Positive confirmation of jumping worms will be almost impossible until the worms are bigger, likely mid-July through autumn. But the rapid and squiggly movement can be a good indicator even in baby worms. You can also inspect your soils and look for the tell-tale coffee grounds texture.
For more information about jumping worms, visit: extension.umn.edu/identify-invasive-species/jumping-worms
Until next time, happy gardening!
Robin Trott is a horticulture educator with University of Minnesota Extension. Contact her at 320-762-3890, or at firstname.lastname@example.org.