A couple of weeks ago I had the good fortune of attending an ASA-SSSA-CSSA
(agronomy) meeting in San Antonio, Texas. It’s a beautiful city built up around
the Alamo with a huge convention center, tons of shops and restaurants, and a most
unique and inviting river walk. The convention center is located next to Hemis
Fair Park, the site of the 1968 World’s Fair, and one can still take an
elevator to the top of the Tower of the Americas to view the city and its
There were many, many interesting speakers and posters. Among the reams of
information I picked up was some interesting facts about an unusually active
type of worm that are proliferating in my dahlia beds. I was talking to Dr.
Josef Gorres from the University of Vermont about his poster on what effects
earthworms have on natural ecosystems when I mentioned these strange acting
worms. He told me they were ‘jumper worms’ (an Amynthas species) which originated in Asia and made their way to
America via the horticultural trade. They were first noticed in Connecticut and
New York in the 1980’s.
Most people were brought up to believe that earthworms are beneficial creatures and in some situations they are. They till
the soil and help break down organic matter and mix it with the soil particles. Doing so improves the soil structure and makes soil chemical conditions
conducive to primarily annual crop plants.
One problem with these worms is that they are an epigeic species which means they live and feed close to the soil surface. These jumper worms, often referred to
as ‘Alabama jumpers’ quickly consume vast quantities of organic matter right on top of the ground, like your mulch or the duff layer of a forest floor. When I
would weed or plant or dig up my dahlias, I noticed the soil was exceptionally well-aggregated and every shovelful seemed to contain a half dozen or more of
these jumper worms. My dahlias do not seem to be adversely affected by the worms so far and probably appreciate the slight increase in pH and calcium
concentration that have been noted in some studies on these worms. But, dahlias are not native to New England.
This same statement cannot be said for some of our native plants, not just in New England but in the Midwest as well. Keep in mind that northern forested
ecosystems developed pretty much without earthworms. The glaciers that came down over the land basically wiped out any earthworm populations. Forests shed
their leaves or needles and in cooler northern climates, these accumulate of the forest floor creating a duff layer. Many species of native plants,
birds, insects, amphibians, microorganisms, and more depend on this duff layer for reproduction, habitat, food and other essentials.
Picture from www.personal.ksu.edu by Dr. Bruce A. Snyder
When invasive earthworms, like the Alabama jumpers, either migrate or are transported to a forested area, they quickly devour the leaf litter and duff
layer. They also alter the soil chemistry favoring exotic invasive plant species like garlic mustard and stiltgrass. Native species of plants and animals decline. There are also cases of
herbaceous perennials, like hostas which are often planted in woodland gardens, declining because of root feeding by these worms.
Some signs of invasion into woodland areas would be a reduction of the forest floor duff layer, fewer or no spring ephemerals (like trilliums and dog-tooth
violets), and even areas in woods with bare mineral soil exposed. Often one will notice non-native invasive plants making their way into the forest. In
light of the other imminent threats to our beloved New England forests including climate change, development, invasive species, and deposition of nutrients
and other materials from the atmosphere, the spread of this and other species of invasive earthworms, does not bode well and we should do our best to educate
ourselves and others about ways to slow their incursion.
To start with, I noticed several websites that had Alabama jumper worms for sale either to use in vermicompost bins or some sites were actually telling folks to
add them to their gardens. One site lauded the fact that these worms are able to survive winters in many northern states! Needless to say, it is not a good
idea to purchase and release these worms into our New England soils. It is also important to try not to move worms when bringing new plants into your gardens
or when giving plants from your gardens to others. Invasive worm species can also be spread by fisherman dumping unused bait into the woods near the lakes
or on the tires of logging trucks and other vehicles.
Also, since these jumper worms have very rapid growth rates, they need copious amounts of organic material. Our gardening practices, therefore, can affect their
populations. Areas with copious amounts of compost or mulch are more likely to be colonized by them. Both compost and mulch are important gardening tools to
many gardeners, including myself, so we need to use them moderately and wisely. Two articles for further reading on this subject are ‘Non-native invasive
earthworms as agents of change in northern temperate forests’ (Front Ecol. Environ. 2004; 2(8):427-435 and ‘Amynthas and Bipalium – Why the Concern?’ at
Garden Variety Invasive Species blog.
A little more than a week after returning from Texas, we were hit by a heavy, late October snowstorm which ruined many Halloween plans and dumped a foot of wet
snow in my neighborhood causing not only massive power outages but colossal tree damage as well. I am hoping to spend this next weekend beginning to clean
up some of the damage. Our old apple tree just pulled up out of the ground, birches were bowing with their tops stuck in the snow, and now I know where yellowwood
got its name.
Until next time,