For the first time ever, the state of Maine has an employee whose sole charge is to control invasive plants.

Nancy Olmstead was hired last year as the invasive plant biologist for the Maine Natural Areas Program in the Department of Agriculture, Conservation and Forestry.

“Invasive plants can overrun our natural areas, out-compete native plants and diminish habitat quality for native species,” she said in a recent interview. “If we don’t take action, our vitally important areas, like salt marshes and flood plains, could be taken over.”

Non-native plants cause all sorts of problems. For example, new research has shown that invasive Japanese barberry provides ideal habitat for white-footed mice, which are a host for the deer tick that causes Lyme disease, she said. Other research has found that invasive common and Japanese buckthorn plants release chemicals that threaten native amphibians – especially worrying as amphibians around the world are facing what scientists have termed an “extinction crisis.”

Compared to other states, Maine is both ahead and behind in its fight against invasives, Olmstead said.

Ahead because our colder temperatures have prevented many invasive plants from reaching Maine thus far. Beyond that, many of Maine’s forests were never cut down for farmland; Olmstead explained that invasives often grown on old farm sites, brought by settlers who planted the nonnative plants they were familiar with from home.

Where Maine is behind is that the state lacks a Do Not Sell list for invasive plants. Maine nurseries may legally still sell such invasive plants such as Japanese barberry and burning bush (popular for its bright red fall color).

One of Olmstead’s first tasks in her new job is to create such a list – she’s working on that now. “It’s just a long road,” she said. “In every other New England state they have that list.”

While such a list would regulate sales, though, Mainers would likely not be required to remove the burning bush plant, say, that has grown in their yard for generations, Olmstead said. (She added that she would not be opposed to friends and family gently nudging homeowners to remove such plants.)

Maine does have one invasive-plant list with the power of law; it regulates aquatic plants. The Department of Environmental Protection works to keep boaters from dispersing aquatic invaders – even a bit of stem or leaf can hitch a ride on a recreational boat and then quickly spread throughout Maine waters.

Olmstead, who studied ecology and environmental sciences at Cornell, worked for the Nature Conservancy, taught labs and other classes at Bowdoin College and completed a field naturalist program at the University of Vermont, does battle with invasives in her off hours, too. At her home, a corner lot in Portland that is mostly lawn with some lilacs, forsythia and a beautiful silver maple, she is “working to get rid of multiflora roses,” she said. “I don’t have any flowering bittersweet vines, but I do have to pull tiny sprouts that come up. And I have a big shrubby honeysuckle that it is going to be a monumental task to get rid of.”

She encouraged other Maine gardeners to do likewise. They can do significant work to help the state fight invasives, she said, suggesting that while they are trapped inside by all the snow, they read the Cooperative Extension’s advisory native plant brochure (available at and dream about what to plant in the spring. Any native tree, shrub or perennial that Maine home gardeners plant from that list could provide habitat for native wildlife and keep invasive plants from finding a place to root.

Another of Olmstead’s early assignments is to launch and then administer an online mapping tool called iMapInvasives. Nine states and the Canadian province of Saskatchewen are involved in the project (so far), which keeps track of invasive plant species by watershed and by county. The maps are online at, and experts with specific knowledge will be able to log in and add information.

“We want to grow the database by bringing in people from other agencies and land trusts,” Olmstead said. “We not only want to follow the distribution of invasive plants on the landscape, but to keep track of treatment efforts at different locations to see if they work.”

Though the task is daunting, Olmstead is optimistic that Maine can one day control – if not eliminate – invasive plants. One instance that gives her hope is that some areas of Kennebec County have no invasive Asiatic bittersweet, and she is finding that “if people monitor and control it, they can keep it out.” That said, the task is harder in southern Maine, she noted, because once an area is cleared of invasives, that nice clearing is like an invitation for new invasives to move in.

Speaking personally, I heard some potentially good news on the invasives front at the New England Grows trade show in Boston earlier this month. Lisa Tewksbury, of the University of Rhode Island Biological Control Lab, said that the moth Hypena opulanta may be able to help eradicate swallow-wort, an invasive plant that has been showing up in coastal areas throughout New England, including in Maine. The swallow-wort vine, a close relative of milkweed, can strangle native plants (including rare ones), and is almost impossible to eradicate by such methods as digging up or removing the pods. Worse, the swallow-wort confuses (at risk) Monarch butterflies, who lay their eggs on its leaves instead of on milkweed, which is their primary food source. But the monarch caterpillars can’t eat the swallow-wort, so they starve.

Tewksbury said the University of Rhode Island has received permission to release the moth on an island near Woods Hole, Massachusetts, as part of a study. The hope is that it will make short work of swallow-wort, because it breeds quickly – going through five generations a year – and has a very limited diet: Its favorite food is the swallow-wort. If the experiment proves effective, the moth could be released elsewhere in a few years, perhaps in Maine.


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