Impact of Invasive Species
Lexington's public lands are filled with aggressive invaders. Several minimally managed areas, such as the woods along Worthen Road, Bowman Park at Pleasant and Watertown Streets, Willards Woods, the margins of the Jack Eddison Memorial Bikeway and the edges of the Great Meadow, are host to an overabundance of invasive species.
Invasive Species Found on Lexington's Public Lands: (Examples and images of
these species may be found at http://nbii-nin.ciesin.columbia.edu/ipane/icat/catalogOfSpecies.do)
- Norway Maple,
- Multiflora Rose,
- Oriental Bittersweet,
- Japanese Knotweed,
- Asian Honeysuckles,
- Burning Bush,
- Garlic Mustard,
- Purple Loosestrife,
- Black Swallowwort and other exotics.
The Commonwealth of Massachusetts has passed legislation that bans the import, sale, or propagation of 140 species of exotic plants. You can find the whole list at the mass.gov website. Many of the plants are weeds that one would not deliberately plant anyway, but there are also many commonly used landscape plants that are no longer permitted as of January 1, 2009.
Please note and avoid planting any of these trees or shrubs:
Norway Maple, including the dark-leafed varieties such as 'Crimson King',
any of the Asian Honeysuckles (Japanese, Amur, Morrow's, Tatarian, or Bell's),
Black Locust, or
Native and Non-native Species
A native plant species in North America is usually defined as one that was present before the arrival of European colonists. These plants shared the environment harmoniously, each with checks and balances to their growth that prevented one species from overwhelming others, and provided a bio-diverse environment supportive of other plants and animals.
A non-native, exotic species may become invasive depending on where it is, and the number of specimens present in an area. A particular plant species might be invasive in one state and not in another, and a single specimen of a non-native plant escaping to a roadside might not be troublesome at all. For instance, Autumn Olive is invasive in Rhode Island, and is not yet invasive in Lexington, but if multiple specimens appear at one site, crowding out other growth, it would be considered invasive.
The pervasive development of land in the last 400 years in New England by agriculture, industry, and the building of roads, parking lots, and buildings has greatly changed the physical structure of much of the landscape. In its disturbed state, the environment is less able to resist certain aggressively growing non-native plants, which may for botanical reasons be able to overwhelm local species.
When a non-native tree such as the Norway Maple (Acer platanoides) is planted on a private property, typically the homeowners mow around it, pull up its seedlings, and take care of the property. In that spot, it is not a problem. However, the great quantities of seed it produces blow around the neighborhood and take root in minimally managed areas – fencerows, hedges, roadsides, property lines, railroad beds, and woodlands. This maple's rapid growth rate, shallow water-gulping root system, very dense canopy and longer growing season soon shade out anything else growing nearby, reducing the numbers of indigenous plants available to supply food to native animal life.
The dangers of unchecked non-native plant invaders, besides the possibility of extinction of plant or animal native species, also include the diminishment of ecosystem functions of importance to humans, such as water filtration, wood production, and recreation, as well as the mounting economic cost of control efforts.
Lexington citizens can be responsible by learning more about invasive species, by eliminating them from their own land so they don't spread to public property, and by replanting native or non-invasive species.