Invasive Plants
What is an invasive plant?
An invasive plant is defined as a plant that is not native to a particular ecosystem, whose introduction does or is likely to cause economic or environmental harm or harm to human health. There are currently approximately 2,100 plant species recorded from Maine. Approximately one third of those are not native. Of those plants that are not native, only a small fraction are considered invasive. Learn more information on the status of invasive plant species known from Maine or find Fact Sheets on these species.
How do these plants reach our landscape?
In many cases, people have imported invasive species for ornamental and landscaping purposes because many of them are very attractive. In other cases, these plant species are purposely planted because they have strong root systems and can provide soil stabilization and prevent erosion. Accidental introduction through hitchhiking on other pants purchased at garden shops and through soil contamination are also possible.
Why are invasive plants so successful on our landscape?
Invasive plant species often lack natural predators, diseases, and other pathogens that keep them in check in their native habitats. They have competitive adaptations including early leaf-out, aggressive reproductive strategies, and efficient dispersal methods. In many cases, they take advantage of disturbances, like road construction, and establish themselves before native species can get a foot hold.
Why should you care?
Invasive species are the second-greatest threat to global biodiversity after loss of habitat. Invading plants out compete native species by hogging sunlight, nutrients, and space. They change animal habitat by eliminating native foods, altering cover, and destroying nesting opportunities. Some invaders are so aggressive they leave no room for our natives.
Invasive plants are a direct threat to what we value about Maine’s natural and working landscapes. Their aggressive growth threatens our recreational experiences. Species like Japanese barberry and multiflora rose can form thorny, impenetrable thickets in forests impacting access. Others can choke water-ways limiting their use. Invaders increase the costs of agriculture and can affect forest regeneration. As if that wasn’t enough, these species will mar the natural beauty of our regionally distinctive landscape, leaving in its place a tangled mess.
What can you do to help?
Our natural landscape is precious. It’s future depends on the choices we make. When buying plants or moving them from place to place consider whether the plants are likely to escape. Plants advertised as fast growing, prolific, and tolerant of many growing conditions are often the ones that become invasive. Maine just won’t be Maine if the plants dominating our landscape are all from away.
- Verify that plants you buy for your yard or garden are not invasive. Ask your local garden supplier to include more native species.
- Replace invasive plants in your garden with non-invasive alternatives.
- When boating, clean your boat thoroughly before transporting it to a different body of water.
- Don't release aquarium plants, fish, live bait, or other exotic animals into the wild.
- Volunteer at your local park, refuge, or other wildlife area to help remove invasive species. Help educate others about the problem.
- Learn what plants are problematic in Maine and tell your state representatives that you care about the future of Maine’s natural landscape.
Outreach and education
The Maine Natural Areas Program (MNAP) provides outreach and education services to help spread the word about invasive plants in Maine. MNAP has worked in conjunction with the Maine Department of Environmental Protection on a rapid assessment aimed at collecting baseline information about aquatic plant species and substrate types commonly found in Maine lakes. The MNAP also produced the Invasive Plant Survey Atlas of Maine which shows the distribution of many invasive plant species known from Maine.
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