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What is an exotic invasive plant?

When many of us see the term “exotic,” what usually comes to mind is something unusual, foreign, or tropical. From an ecological perspective, however, the term “exotic” means that the plant is foreign or non-native to a certain region. Due to various adaptations, climatic conditions, and other factors, certain exotic plants have a competitive advantage over native plants. An exotic plant is considered “invasive” when the plant displaces native plants, degrading the ecosystem.

Urban Wilds Youth Summer Crew working on restoring native plants to Sherrin Street Woods. Invasive garlic mustard and black locust trees dominate the landscape in this section

People have introduced almost all of the exotic invasive plants that are found in Eastern Massachusetts. These plants are commonly grown and sold as ornamentals for yard and garden, like winged burningbush and Japanese barberry. Some are favored as street trees like Norway maple. Still others have been promoted as plants to prevent erosion, like multiflora rose, or to solve other environmental problems.

Exotic invasive plants pose a serious threat to all native plant communities in New England. Urban natural areas are often the most deeply affected because they are more disturbed and the parcels of land are smaller. The urban wilds that contain the most exotic invasive plants are those that were once cleared for house lots, roads, or industrial use. These kinds of sites were abandoned and managed to lie fallow long enough to re-grow with a mix of natives and exotics. However, many sites now contain stands of densely growing, even-aged Norway Maples with little to no understory. Other sites, such as the 90-acre Allandale Woods in Jamaica Plain, have been left undisturbed for more than a century. The interior of Allandale Woods is a fairly intact Oak/Maple/Ash second-growth forest with a rich understory mostly consisting of native plants. However, the edges of Allandale Woods are slowly giving way to exotic invasive plants like Norway maples, European buckthorn, and Japanese Knotweed.

While there are measures in place to restrict the trade of some of these species, mostly it is up to consumers and the nursery trade to prevent the planting of exotic invasives. This requires knowledge of which plants can be considered as invasives in a particular region. Go to EarthWorks Guide to Invasive Plants and Native Alternatives in Eastern Massachusetts to get information about some of the worst invasive plants in our area and what you can plant in their stead. This page also includes a list of native alternatives to plant that have some or all of the characteristics that you might find desirable in the invasive plant. Please also look at our list of links for more extensive resources on exotic invasive species.

For information on various invasive species topics please check out the following articles from the EarthWorker, EarthWorks’ newsletter:

“Why is EarthWorks Removing Trees”

"Profile of the Invasive Norway Maple"

Also, see the photo series results of invasives removal and native tree restoration projects.

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