Non-native invaders of our habitat garden

Japanese beetle  ©Janet Allen
Japanese beetle: The first invasive insect we knew about

Just as with plants, some non-native creatures invade our habitat garden.

That cats, some non-native insects and even some non-native birds are invasive didn't surprise us, but earthworms? Now that was a shock!

WOW! Earthworms aren't native!

Worms ©Janet AllenEarthworms in our soil

Most people are surprised—astonished and unbelieving would probably be a better description—to learn that the lowly earthworm is a huge danger to our natural areas.

I was pretty shocked myself when I first learned this, reading William Cullina's Wildflowers book on p. 17. I returned to these pages every couple of weeks for a while, certain that I had misread it.

But no, it's true. In the areas of North America covered with glaciers, plants evolved without earthworms. This area includes Central New York (and along about February it's not hard to believe we were covered with glaciers …) The earthworms that are here today were brought, intentionally or not, from Europe.

Edible garden soil  ©Janet Allen
Edible garden soil

What makes it so hard to believe that earthworms are non-native invaders is that we all grew up being told that earthworms are good for gardens.

And why are they good for gardens?

Because they help mix the soil, pulling organic material down into their burrows. That IS a good thing for gardens, especially for our edible garden.

Duff layer in Adirondacks  ©Janet Allen
Some duff layer in the Adirondacks

But think about our forests. The "duff layer" on the top of the soil was there when our woodland plants evolved, and they grow best with that layer in place. That's where earthworms cause problems, not in our gardens. (See the Great Lakes Worm Watch in the sidebar to see amazing photos of natural areas with and without worms.)

There's not a lot we can do in our yard about this issue since we don't live near natural areas. Neither are we fishermen, so we don't have to be warned not to let extra earthworms loose in the wild, but it's good to be aware of the problem.