When the landscape is free of foliage in late winter, it’s a good time to walk your property in search invasive plants including woody growths like Asiatic bittersweet that just might choke the life out of your trees come spring.
Among the bare trees, it’s easy to spot this invasive vine winding around trunks. And as the weather warms, you can trace the destructive plant back to its roots and yank it from the damp soil.
This tip, along with several others, was recently included in a news release by the Maine Department of Agriculture, Conservation and Forestry in recognition of National Invasive Species Awareness Week, Feb. 26 through March 2.
Asiatic bittersweet, also known as Oriental bittersweet, is just one of many invasive species that destroy habitats in Maine.
“It’s a woody vine that climbs trees and shrubs and can even sprawl cross the ground,” said Nancy Olmstead, invasive plant biologist for the Maine Natural Areas Program. “It can kill trees by girdling them, and it can climb up through a fairly closed forest canopy and spread out over the canopy to grab the light.”
You can see the vine invading the forest along Interstate 95, said Olmstead, weighing down trees and snapping off branches. It’s taken over the banks of the Royal River in Yarmouth, its thick woody stems roping around tree trunks like a snake, its bright red berries shining in the sun.
A familiar foe to gardeners, foresters and trail maintainers throughout Maine, Asiatic bittersweet is here to stay. There’s no hope it could ever be eradicated from the state, Olmstead said. It’s too widespread, hardy and fast-growing to be erased from the landscape. But with a few management strategies and vigilance, it can be kept at bay.
“Management strategies really depend on the situation,” said Olmstead. “But we can have a goal, for example, to allow trees to grow normally. So perhaps you go out a couple times a year to cut the vines so they don’t get a chance to get up into the trees and girdle them. I also prevent the vines from fruiting so their seeds are spread by birds. Again, you do this by cutting them regularly.”
Strategies for controlling invasive plants vary depending on the species, its abundance, and the goals of the landowner, Olmstead said. To help landowners, the Maine Natural Areas Program provides online invasive plant photo gallery filled with information about how to identify invasive plants and ways to manage them, including videos.
“It can be a process, but the first step is getting out there and finding out what plants are on your property, how much, and where they are,” Olmstead said.
There are currently about 2,100 plant species recorded in Maine, and about a third of those are not native. But of those plants that aren’t native, only a small fraction are considered “invasive.”
But what makes a plant invasive in the first place? The answer isn’t cut and dry. At the state level, each potentially invasive species is evaluated on certain criteria, such as the plant’s potential rapid growth and widespread dispersion, Olmstead said. But in general, an invasive plant is not native to the area and when introduced to that area causes economic or environmental harm or harm to human health.
Last year, the state of Maine enacted new rules that ban the sale and distribution of 33 plants that had been deemed invasive, and that list included Asiatic bittersweet, Japanese knotweed, glossy buckthorn, purple loosestrife, black locust and more. This is something to keep in mind when purchasing plants for your gardens this spring. DACF suggests that people landscape with as many native plants as possible.
“What we know is that in many places, invasive plant presence correlates with human activity on the landscape,” Olmstead said. “As more of Maine has experienced development, people are seeing invasive plants spread in those areas.”
In addition to these terrestrial invasive plants — those that live on land — there are 11 aquatic invasive plants that are currently listed as imminent threats to Maine waters by the Maine Volunteer Lake Monitoring Program, and there is a state law that prohibits the sale and transport of those plants in Maine. Photos and descriptions of all of these invasive plants are available at https://www.mainevlmp.org, where you can learn about monitoring for these plants in local lakes and ponds.
Invasive forest insects are another problem in Maine. Of chief concern are the emerald ash borer, Asian longhorned beetle, brown spruce longhorn beetle, hemlock woolly adelgid, elongate hemlock scale and winter moth. These pests attack specific trees and woody shrubs, as described in an online Insect Survey Guide provided by the Maine Department of Agriculture, Conservation and Forestry and Maine Forest Service.
“We want to know where these [invasive insects] are so we can keep track of infestations and maybe be able to contain the infestation, depending on the insect,” said Jim Dill, pest management specialist with the University of Maine Cooperative Extension. “We need the citizens to be our eyes and ears because we can’t be everywhere.”
Another thing Maine residents can do to prevent the spread of invasive insects is avoid transporting firewood. Instead, when camping season rolls around, purchase firewood at or near your camping location.
Also, if you live in an area where winter moth has been found, don’t dig up and share perennials and tree saplings this spring. Moth pupae hides in the soil and may be moved with the transplants, spreading the infestation to a new area in the state.
And when it comes to invasive plants, Olmstead suggests people take action by surveying their own property first.
“It allows you to directly go out there and look at the plants and get experience pulling them, cutting them or treating them,” Olmstead said.
Beyond that, people can take action by contacting local conservation organizations, such as land trusts, to ask how they can help manage invasive species on nearby parks and preserves, Olmstead suggested. In a public forest, to get control of something as hardy as Asiatic bittersweet, it often takes a lot of volunteer power and persistence. But the alternative is forest dragged down and destroyed, one tree at a time.
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