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As a gardener, I know humans have introduced many invasive species like Dandelions, Japanese Knotweed, and Phragmites, into many of our native North American habitats. I have witnessed it, and to some extent participated (in ignorance) of the problem.
As little as two hundred years ago the forests surrounding the Great Lakes lacked earthworms. The Ice Age and glaciers eliminated the native species, and during the 10,000 years since the last glacier, our trees and plants evolved to live in the wormless local soils. This became a thick layer of duff or the debris of trees and shrubs that lined the forest floor. Duff remains for years, slowly decayed by fungi, but providing a habitat for many Michigan ferns, delicate wildflowers, and small animals like salamanders.
Since settlers first moved into this area, they introduced European earthworms like the red wriggler to encourage composting. Gardeners still think of worms as a desirable asset to their garden’s soil. These worms eat decaying matter, aerate the soil, and leave humus-rich worm casting behind as they burrow. In general, they do good things for garden soil.
In the forests, however, worms eat the duff in as little as two years, lowering the soil’s acidity and making nutrients more available. The plants in our forests survived in the poor fertility and the high acidity of our original native soils. While the introduction of worms won’t necessarily harm the mature trees growing there, the duff’s absence affects the number of seedlings growing in an area. It also makes an advantageous situation for unwanted invasive species that couldn’t have grown in the more acidic original soil.
Bloodroot
As this debris layer disappears, so does the habitat for plants like Trillium, Solomon’s Seal, Blue Cohosh, Sweet Cicely, Mayflowers, Wild Ginger, Lady Fern, Bloodroot, Bellwort, and the tiny Goblin Fern which might already be extinct in this area. They adapted to germination and growth in the thick layer of duff that provided them nutrients, moisture, protection from extremes in temperature and predators, and microorganisms like fungi necessary for their survival.
It is also believed the loss of the duff effects the salamander population that fed on insects living in the debris. The salamanders, in turn, provided food for snakes, shrews, thrushes, and screech owls, so the earthworm invasion affects a whole chain of living organisms.
Worms were introduced from dumped fishing bait, on the root-soil clumps of purchased plants, and on the tires of vehicles entering the local forest. The most severe invasions are usually near roads. This is one reason the U.S. Forest Service is restricting logging and road-building in certain forest areas in states around the Great Lakes.
Trillium
Once the earthworms infest an area, little can be done to remove them without doing more harm to the forest. We know many of the above plants grow in worm-infested soil because we grow them in our gardens, but a study in the Chippewa National Forest in northern Minnesota showed these species do not return to worm-infested forests.
Some ecologists hope the ecosystem of the forest may eventually come to a new balance. In the meantime, don’t spread earthworms into wormless areas, don’t dump worm bait in forested lands, and keep your vehicles on roads and trails. Gardeners in wooded areas need to keep compost piles and worm contaminated soil from contaminating the woodlands. These may seem like small measures, but it was a little thing that started this change.
(Updated. Originally published in the Cadillac News in 2002.
In July we took out granddaughter to New York City. Day one we went to the Medieval art museum, the Cloisters, on the northern tip of Manhattan. I’ve traveled the NYC subway system before, but this trip was unusual. Our train stopped, everyone was told to get off, and we were left to find our own way. A friendly New Yorker led us one level down to 1 Train. (Definitely not your Times Square station type of stop; kind of scary.) Anyhow, after a taxi ride and a walk through the park surrounding the museum we arrived.
Cloisters
The Cloisters, besides housing some wonderful sculpture, tapestry, and painted art, plus The Belles Heures of Jean de France, Duc de Berry, a handmade and painted prayer book (heaven for a calligrapher to view), has an herb garden typical to the times (13-15th centuries AD). I’m wandering through the beds seeing how many of the plants I grow, when I come across… a weed! Plantain! Growing in the immaculate beds of the Cloisters.
I stopped. What?
Plantain in the Cloisters’ herb bed.
I had to get close just to make sure.
So the plantain growing in my driveway is another useful weed brought by colonists? Seems so — Plantago major, a common, pervasive weed.
On returning home I checked out my copy of Pamela Jones Just Weeds (you’d think I’d have known this information already from perusing this book) and there it was listed, a plant that literally followed the footsteps of the Roman army, although she admits the boundaries between fact and fiction about this plant are blurred. According to Jones’ entry: ‘Leaves, roots, and seeds of plantain, fresh or dried, have been used for centuries in the treatment of such varied ailments as poison wounds, asthma, dysentery, earache, and kidney disorders. Rich in potassium salts, plantain is regarded as one of the finest remedies for cuts, abrasions, infections, ulcerations and chronic problems of the skin.’ According to her it can even heal other plants — she tried it on a fruit tree with blight and it worked!
Plantain is also edible. The new leaves can be used like spinach. Older ones are tough. Plantain contains healthy amounts of Vitamin A, C, calcium, and iron. I’m trying out a recipe for a skin salve, too, since claims make it sound like a panacea for skin injuries and disorders. Food and medical recipes can be found all over the internet. Guess I just wasn’t looking!
Rhobin's Garden 