What Are Invasive Plants?

Non-native or “exotic” species are plants introduced into regions of the world where they have not lived before, very often from other continents. They may or may not become invasive. Some scientists estimate that about 25-30% of the non-native species that have been introduced to the United States have now become invasive somewhere in this country.

Invasive species are non-native plants that grow very rapidly and out of control, and do real damage to the ecosystem where they have been introduced. Away from the diseases and predators that helped to keep them in check in their home environments, they are so aggressive that they quickly out-compete native species and significantly alter ecosystem relationships. Their dominance reduces biodiversity—threatening or eliminating local plant and animal species. Often, they spread extensively enough to form “monocultures,” areas where they literally are the only plant growing.

A particular exotic or introduced species might be invasive in one part of the United States but not another. Because it takes some time for any species to spread and get established, it might first show its invasive behavior where it was originally introduced, and is only a matter of time before it spreads enough to become invasive elsewhere. In this scenario, the invasive range will grow over time. It is also possible that a species will be more invasive in one ecosystem, but less so in another, because different conditions in the two places may alter its behavior and effect upon the biology of the different sytems.

Invasive plants are not the same things as "weeds." To a gardener, a weed is a plant out of place— not desired or wanted in their landscape. But that doesn't mean that this "weed" has the serious ecological impact that an invasive plant does, e.g. dandelions are "weeds" to many people, but not they are not invasive plants.

Our understanding of plant and animal invasions is somewhat recent in ecosystem science. After all, it is only in the past few centuries that we humans have been moving species around the planet rapidly and over long distances, on ships, trains, automobiles, and planes. The word "invasive" with respect to living organisms, entered our lexicon after the publication in 1958 of ecologist Charles Elton's book, The Ecology of Invasions By Animals and Plants. It was the first comprehensive look at the subject.

  • Learning About Invasive Plants in Massachusetts
    A Guide to Invasive Plants in Massachusetts book cover

    The Prohibited Plant List

    Massachusetts has a significant number of invasive plant species, regulated by the Department of Natural Resources through the state's Prohibited Plant List. These plants do damage to both our environment and our economy, and it is illegal to import, sell, propagate, or trade any of these plants anywhere in the state. Many of the plants on this list were first rigorously evaluated through the work of the Massachusetts Invasive Plant Advisory Group (MIPAG)— a collaborative group representing a diversity of stakeholders in government, academia, the nursery industry, and conservation organizations.

    There are additional species, not on the regulated list, that some conservation professionals and skilled landscapers choose not to use and also consider invasive. But even without such additions, close to 10% of the non-native plant species introduced into the Commonwealth are now legally designated as invasive.

    Purchase this Guide to Invasive Plants in Massachusetts. (It contains most of the listed invasive species found in Massachusetts.)

  • Regulating Invasive Plants in Massachusetts

    The Prohibited Plant List currently includes approximately 145 non-native species. Managed by the Massachusetts Department of Agricultural Resources (MDAR), the associated regulations prohibit the production, sale, transport, or exchange of these plants. These rules first took effect on January 1, 2006, with a phase-in period until January 2009 for a few species still in nursery production. Sixty-nine of the current listed species were recommended for inclusion on the list by MIPAG, after being evaluated for invasiveness using detailed scientific criteria. The remaining listed species are federally designated noxious weeds, governed by regulations that apply throughout the United States.

    • The Massachusetts Invasive Plant Advisory Group (MIPAG) was formed in 1995 as concern over invasive plants was rapidly growing. It includes representatives from both federal and state governments, private land trusts and conservation organizations, the nursery and landscaping industries, the scientific community, and academia. Working as a collaborative body and seeking consensus as much as possible, MIPAG's original recommendations for designating invasive plant species were made to the appropriate state agencies in 2005. Periodically the committee recommends the addition of new species to the list, subject to MDAR approval.
    • Noxious Weeds are federally designated by the United States Department of Agriculture (USDA) as species that can damage crops (including nursery stock or plant products), livestock, natural resources, the public health, or the environment. It is illegal to import such plants to new areas or to transport them across state lines. Fortunately, many of these designated species are not yet found in Massachusetts.

    Know Your Plants!

    If you don't know it, don't grow it. Get to know the plants you garden with. Find out if they are native or non-native. Learn about their history and growing characteristics. Emphasize natives in your planting for the health of our common ecosystem. And if you decide to plant a non-native, be sure it isn’t already classified as invasive, or suspected of becoming invasive. You will love the results—more songbirds, butterflies, and lots of beauty all around.