Invasive Species

Invasive Species in our Yards and Gardens

What are they and how can we manage them?

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knotweed

Invasive Species

In our efforts to promote and support native species in our gardens, we start to notice how many non-native species are present—both those we may have planted deliberately and those that have arrived through accidental introduction. Not all non-native species become invasive; in fact, the majority do not. Only those that aggressively grow, multiply, and out-compete or heavily consume our native species deserve the label “invasive.”

Why are some species invasive while others are not? There are a few characteristics and circumstances which combine to create opportunities for a species to become invasive. When species are moved to a new region that lacks the consumers (herbivores for plants, predators for insects) and diseases that controlled their populations in their native range, their growth or spread is no longer constrained. Successfully invading species typically have a life strategy of growing fast and having high fecundity (producing many seeds or eggs). The conditions we create, especially with disturbed or degraded native communities, present opportunities for such species to establish, grow in population size, and outcompete our native species for resources.

spotted lanternfly ©Mass DAR

Why Should We Care About Invasive Species?

In their native environments, these species evolved as part of complex food webs that tend to keep any one species from growing wildly and becoming dominant. But in a new location, without those natural checks and where the environment is otherwise conducive to growth, these species can become invasive, disrupting the complex web of life that evolved there. Invasive plants can dominate patches of ground, suppressing native species and the life that depends on them. Invasive insects and other animals can overwhelm species that have insufficient defenses against these new arrivals, also disrupting food webs and relationships. The result is that our native species suffer and the rich, interdependent relationships of our ecosystems become poorer and weaker.

It is unrealistic to think that we can rid Massachusetts of invasive species. But every patch of ground where we can reduce or eliminate them helps because it removes a source of new generations that can spread, and, if re-planted with native species, provides more habitat supportive of our native wildlife.

Invasives can be roughly divided into two categories:

· One group has been here long enough to become widely dispersed and well established in our landscape. Think knotweed or bittersweet. Unless and until some biological control agent is developed and released, we’re never going to eliminate these from the wild. But we can keep them out of our gardens and other targeted locations, reducing their spread and influence and maintaining refugia for our native species.

· The other group is recently arrived species, where identification and quick action can help prevent the establishment and spread of these species. Here, vigilance is key and quick reporting essential. Think spotted lanternfly or mile-a-minute vine (that name alone is scary, isn’t it?) The Massachusetts Introduced Pests Outreach Project, a collaboration of the Mass. Department of Agricultural Resources and UMass, maintains a website and reporting system with lots of information about species of greatest concern.

lesser celandine

Invasive Plants

Invasive plants typically have been brought to the United States through the nursery trade, either intentionally as landscape specimens or sometimes unintentionally as seeds or smaller seedlings.

Of all 2,263 plants that have been identified in Massachusetts, about 725 are non-native and considered naturalized (i.e. introduced directly or indirectly by humans and have established populations). Of those, 69 plant species have been classified by the Massachusetts Invasive Plant Advisory Group (MIPAG) as "Invasive," "Likely Invasive," or "Potentially Invasive." Many of these species are now prohibited from import, sale, or trade in Massachusetts by the Mass. Department of Agricultural Resources.

Some of these invasive plants are particularly problematic here in Massachusetts. You may well have seen one or more of them in your own yard or on your street. See the links below for pictures and more information about these, including suggested methods of control.


Lesser celandine Ficaria verna –ALERT click here for more information.

Japanese knotweed Reynoutria japonica –Grows to 6-8’ in colonies so dense that virtually no other plants can survive. The plant has a vigorous system of extremely long roots that makes removal of the plant challenging.

Bittersweet vine Celastrus orbiculatus –an invasive vine frequently found along roadsides and forest edges. If allowed to grow, bittersweet vines can take over wide areas, aggressively smothering out native trees and shrubs.

Glossy buckthorn Frangula alnus –a woody shrub or small tree that can form dense stands in forests and formerly open areas. It spreads aggressively and threatens forests and wetlands by outcompeting native species for nutrients, light, and moisture.

Multiflora rose Rosa multiflora –a climbing or rambling shrub with single or multiple arching stems that can grow 10-15 feet tall. It produces a large number of hips (seed pods) that get distributed by the birds. It often forms dense thickets that prevent native shrubs and herbs from establishing.

Burning bush Euonymus alatus –this shrub has been popular with gardeners because of its crimson red color in the fall. However, the plant reseeds easily and tends to escape our yards and invade nearby forests and open fields, where it outcompetes native plant species that provide food and shelter essential for birds and other wildlife.

Garlic mustard Alliaria petiolate –a bi-annual plant that readily invades wooded habitats and spreads by seed. The plants produce a toxin that kills soil fungi that our native plants depend on. Annual pulling each spring (April-early May) before the flowers set seed is a way to eventually halt its spread. This is a great activity for kids.

Black swallow-wort Cynanchum louiseae -a perennial vine in the milkweed family with small, black-purple flowers and dark green shiny leaves. Very fast-growing, the plant out-competes native vegetation, reducing native plant diversity and wildlife habitat. Monarch Butterflies mistake this plant for common milkweed but its caterpillars cannot fully develop on it.

More comprehensive lists of invasive plants, along with photos that aid identification and information about their biology and control, are published on the web by Mass Audubon, the Lexington Conservation Commission, and CISMA (the Cooperative Invasives Species Management Area of the Concord-Sudbury-Assabet watersheds).

A word about herbicides: Many authorities recommend the prudent, limited use of pesticides to control some invasives, particularly with large, well-established populations and where the owner’s time is limited. In small areas like gardens, though, most of these invasive plants can be controlled or even eliminated with diligent cutting or digging. For those who are leery of the health and environmental impacts of herbicides, and who are willing to invest the time and energy to control these manually, we recommend trying to do it without chemicals, as we do in our own gardens.

Invasive Insects

Massachusetts is also impacted by invasive animal species, including quite a few insect species. Some you may have heard of include winter moth, viburnum leaf beetle, emerald ash borer, Asian longhorn beetle, and Sirex woodwasp. The USDA Invasive Species Information Center and the Mass Introduced Pests Resource Project are good sources for more information about insect pests of concern in Massachusetts.


Release from predator population control is a feature of most insect invasions. Parasitic wasps and flies play an important role in predator pressure in most insect communities, but they are highly specialized on what prey they attack. The biological control approach of importing a highly specialized parasitic species to control an invasive species is a complex process that takes years to develop, but at times has had great success. Successful establishment of a tachinid fly species a few years ago seems to be well on its way to controlling our winter moth problem. If you have previously hired a tree company to chemically control for winter moth, you may be able to stop that practice now.

Of particular concern in Massachusetts right now is the Spotted lanternfly. (Click here for an ALERT statement.) This is a relatively recent arrival, first found in 2014 in Pennsylvania, where it has impacted fruit trees, plant nurseries, and the timber industry, resulting in huge economic losses. It is a broader ecological problem because of the breadth of plant species it can eat. It has since spread through many states on the eastern seaboard. While not widespread in Massachusetts yet, this insect spotted in Fitchburg and a few other locations in the state in 2021. More information about the spotted lanternfly, and what to do if you see it, can be found through UMass, the Mass Dept of Agricultural Resources, and the Ecological Landscape Alliance.

Other Invaders

Among animal species, another cause for concern is the recently arrived jumping worm, Amynthas agrestis. This new type of earthworm is problematic for its unusual habit of consuming surface level organic matter, making it unavailable for plants. You can distinguish between these jumping worms and other earthworms by the white band on its clitellum, its jumping/wriggling movement, and the coffee ground appearance of surface soil where they have established. More information about jumping worms can be found here.