We've learned over time that worms improve soil. They help aerate the soil by tunneling and they fertilize with their waste, called castings. And that is all true of the nightcrawlers we are familiar with.
But Homegrown NH host Emma Erler, lead horticulturalist at Kirkwood Gardens, says you should be taking a closer look at the worms in your garden.
There is now an invasive species of worm, called jumping worms (Amynthas agrestis), which actually cause damage to the soil and threaten ecosystems.
“You can see the effect on the soil or the compost, so the soil becomes very loose and crumbly, which makes it difficult for plants that have very fine roots to sometimes survive.”Emma Erler
Erler says jumping worms have been found throughout the state of New Hampshire.
What do they look like?
They can be identified by the movement that gives them their name.
“They move very quickly, kind of a snakelike, slithering, very abrupt movement,” says Erler. “If you're in your garden and get startled by a worm, it's probably a jumping worm.”
They also have a prominent band around the body called the clitellum, which is milky white to light gray. On European earthworms this band is reddish brown.
What do they do?
They are voracious eaters, according to Erler. “Their castings are nutrient dense, but those nutrients tend to leach out of the soil very quickly.”
Jumping worms live in the leaf litter or the topmost layer of the soil, in the organic matter that protects the soil from erosion. In the garden, jumping worms will quickly devour mulch and destroy the soil surface and mycelium.
Shallow-rooted plants have a hard time becoming established. It also makes it difficult for wildflower species and even trees to become established from seed and destroys habitat that is important for native insects and birds.
How would I know if they are in your soil or compost, or a plant you buy?
Erler recommends checking plants you bring into your garden for coffee ground-like soil or worms themselves.
If you buy mulch and soil or compost in bulk, make sure it’s been heat-treated to a core temperature of 130F for at least three days to eradicate jumping worms and cocoons.
How can I control them?
“You're going to be looking to limit the numbers more than actually eradicate these worms,” says Erler. “Jumping worms are very difficult to eradicate once established.”
Small populations of jumping worms can be managed by handpicking and destroying the adults.
Erler says she does this while weeding. “I'm often disturbing the worms,” she says, “and as they're coming out of the soil or the mulch, I just throw them in a plastic bag, and that goes to the dump.”
Erler says you can take a more active approach by making a mustard solution ( ⅓ cup yellow mustard powder in a gallon of water) and drenching the area, driving the worms to the surface and making it easier to hand pick them.
Jumping worms are annual – the adults die after the first freeze. Their cocoons, containing the eggs, survive the winter, hatching in the spring.
It is important to destroy the cocoons, which are sensitive to heat and can be eradicated using black plastic.
In late spring or summer, Erler recommends covering moistened soil with plastic for several weeks, or until the soil temperature exceeds 104 degrees for at least three days (big commercial piles need to be hotter). “The hotter the better,” she says.
“Don't panic,” says Erler. “They're everywhere, and to a certain extent they may be inevitable for gardeners. Just monitor for them, do some hand picking. And it's going to be okay.”
See you in the garden!
If you have a gardening question for Homegrown NH, email or send a voice memo to HomegrownNH@NHPR.org.
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
If you have a gardening question for Homegrown NH, email or send a voice memo to HomegrownNH@NHPR.org.
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
