WHAT ARE INVASIVE TREES?
Non-native plants have been introduced to this continent since colonial times. Some were brought here on purpose as agricultural or ornamental plants. Others arrived accidentally, for example as seeds or root fragments mix with soil or animal feed.
The vast majority of non-native plants stay within the confines of the farm or garden in which they have been planted. Others, such as Queen Anne’s Lace and dandelions, have naturalized and become a part of our landscapes.
But a third group of non-native plants, those that have spread widely in their new environment or have the potential to do so, are a major concern. Usually, invasive plants get a foothold in areas that have been disturbed by human activity and then move out into natural areas, where they displace native vegetation and change wildlife habitats.
The Norway Maple is an example of an invasive tree. It was introduced into this country from Europe in 1756 and has been widely planted as a tough shade and street tree. It wasn’t until the early 1900s that its invasive potential was recognized. Norway Maples produce copious seeds that can germinate and grow strongly even in the shade under an established tree canopy. Their roots are shallow and very dense root system, and they cast a very deep shade. They leaf out early and lose their leaves later than native trees, giving them a longer growing season that provides them a competitive advantage. Many native wildflowers, as well as shrubs and trees, can’t grow in the changed environment that Norway Maples create and so get crowded out.
WHY ARE INVASIVE PLANTS “BAD”?
Natural communities, or ecosystems, whether local ones or larger, are a complex web of life in which plant and animal species have evolved together, function together as a whole, and depend on one another.
Invasive plants disrupt healthy ecosystems by crowding out and causing the loss of native plant and animal species. The resulting loss of biodiversity compromises the health of the ecosystem.
CHARACTERISTICS OF INVASIVE TREES AND OTHER INVASIVE PLANTS
Given the harm that invasive plants can cause, it is important to be able to gauge whether an introduced plant might become invasive in its new environment. There can be no prediction with absolute certainty, but certain characteristics are markers for invasive potential. According to the United States National Arboretum, invasive plants:
- Produce large numbers of new plants each season
- Tolerate many soil types and weather conditions
- Spread easily and efficiently, usually by wind, water, or animals
- Grow rapidly, allowing them to displace slower growing plants
- Spread rampantly when they are free of the natural checks and balances found in their native range
INVASIVE TREES IN MASSACHUSETTS
The Commonwealth of Massachusetts has recognized the need to control invasive plants. According to the website of the Massachusetts Department of Agricultural Resources:
“On January 1st, 2006, the Department began a two-step ban on the importation and sale of more than 140 plants identified as either noxious and/or invasive in the Commonwealth. The list of plants was developed in collaboration with the Massachusetts Invasive Plants Advisory Group (MIPAG). MIPAG members represent research institutions, non-profit organizations, green industry businesses and associations, and state and federal agencies. The MIPAG list is a product of scientific analysis and represents the scientific consensus of groups and individuals with a broad range of perspectives on the subject of invasive plants.
Effective January 1, 2009, all plants on the prohibited list are banned from importation, propagation or sale within the state of Massachusetts.
The ban is limited to the importation, sale, trade, distribution and related activities of these plants, and does not impact any existing plantings.”
The Massachusetts Prohibited Plant List, effective January 1, 2009, includes the following invasive tree species:
Amur cork-tree (Phellodendron amurense)
Black locust(Robinia pseudoacacia)
Common buckthorn (Rhamnus cathartica)
European buckthorn, glossy buckthorn (Frangula alnus)
Norway maple (Acer platanoides)
Sycamore maple (Acer pseudoplatanus)
Tree of heaven (Ailanthus altissima)
HOW CAN I LEARN MORE?
Information on the Web
MA Prohibited Plant List, effective January 1, 2009
Information in Print
Randall, John M., and Janet Marinelli. Invasive Plants: Weeds of the Global Garden. Brooklyn, NY: Brooklyn Botanic Garden, 1996.