MARCH 10, 2022

More and more gardeners have become aware that there’s a new pest to be watch out for: jumping worms.

The worms live in the top 2” of soil and voraciously consume organic matter like leaves and mulch, turning the soil into what looks like coffee grounds. This makes erosion and plant ­damage likely, and removes nutrients from the soil.

How do they spread?

Two common gardening ­practices spread jumping worms and their tiny egg cocoons:

  • If you get a plant dug from a friend’s garden or from a ­garden club’s plant swap and it still has any soil on its roots, you may be introducing the worms into your garden soil if its home soil has an infestation.
  • If you use wood mulch or wood chips around your plants, the worms and eggs can live in that.

As far as is known now, only heat of about 90° kills the worms and 115° kills the cocoons. Researchers believe the worms are killed by our winters, but the egg cocoons survive in the top two inches of soil to hatch the next year.

What about the plant sale?

So, what about plants ­purchased from nurseries, ­garden centers, and particularly the Friends School Plant Sale?

All of the growers for the Friends School Plant Sale are certified by the Minnesota Nursery and Landscape Assoc­iation (or their own state’s equivalent) and therefore use soil-free potting mixes, rather than soil from the ground.

Even before the jumping worm problem, MNLA ­members have been greatly ­concerned about not spreading plant diseases through potting soil, tools, and plant materials. Their businesses depend on having their practices and plants inspected. We have paperwork from our growers stating that they are inspected by the Minnesota Department of Agriculture each year.

What can you do?

Prevention is the only ­possibility right now.

Researchers at the University of Minnesota are working to find possible treatments, but it’s not known if there will be one, or whether it will be acceptable for use by many ­gardeners even if they do.

Inform yourself with these Minnesota-based resources:

IDing the worms

Jumping worms start small when they hatch from tiny eggs in the spring. They cannot be confidently identified until they grow larger and mature in late July–early August. At that point, if you suspect jumping worms, please send high-resolution photos with a clear view of the segments between the mouth and clitellum (the ring around the body) directly to [email protected] at the DNR for identification.