As The Worm Turns

Jumping for joy is not how I would describe anyone who meets jumping worms.  Quite the opposite.  Many are grossed out, not a few are thinking of giving up gardening and one gentleman phone caller denounced not only the invasive species website but several government agencies which are probably not involved.  These worms are prolific, bold, and popping up in new places every day.  If you haven’t experienced them yet, you certainly haven’t been hiding under a rock, or anywhere else near the soil.

As gardeners, we are taught that earthworms are good guys.  As they break down organic matter by ingesting it, nutrients plants can use are released.  Earthworm tunneling reduces soil compaction, yet their castings help soil stick together and resist erosion.  Other than the “ew” factor, what’s not to love? 

But jumping worms, including the most well-known species named Amynthas, are not good citizens of the soil.  These Asian imports grow quickly, reproduce rapidly and create large populations of themselves.  They accelerate the breakdown of leaf litter faster than it can accumulate on the forest floor, leaving bare soil.  In turn, soil temperature and moisture buffering decreases, seeds for new plants don’t germinate and beneficial soil organisms suffer.  I only have to look at the woods behind my house to see this, where there are very few young native trees coming up to replace the old fellows and virtually no shrubs or understory plants.  But the bad news doesn’t stop there, according to the folks at Great Lakes Worm Watch, part of the University of Minnesota.  They write, “There is also fascinating evidence emerging that the changes caused by exotic earthworms may lead to a cascade of other changes in the forest that affect small mammal, bird and amphibian populations, increase the impacts of herbivores like white-tailed deer, and facilitate invasions of other exotic species such as European slugs and exotic plants like buckthorn and garlic mustard.”  In gardens and on lawns, jumping worms leave castings resembling coffee grounds and sometimes cause plant decline and soil subsidence.  Occasionally hundreds of jumpers end up on sidewalks or in basements. 

Jumping worms not only leap, but wiggle manically when disturbed, flipping like a fish out of water, and can cruise across a lawn like a snake with an agenda.  If you’re familiar with standard earthworm behavior, the show put on by a jumping worm is sure to shock and surprise.  For identification purposes, also look carefully.  A mature specimen of a jumping-type species will measure one and one-half to eight inches long, and will have a smooth, milky pink or white to gray band (clitellum) near the head.  Other worms have a raised or saddle-shaped, segmented clitellum and a more ho-hum demeanor.  In our area, they spend the winter as tiny cocoons, first appear as adults in spring, and grow until soils cool in fall.  Last year’s spring drought suppressed them, while this year’s excessive rainfall favored them.  Control options, beyond picking and destroying, are not well-developed.  Frustrating and alarming, indeed.