An invasive plant is a non-native species that has been introduced, either intentionally or accidentally into a new habitat or has escaped cultivation. Because they have not evolved in this new habitat they lack natural methods of control and can spread aggressively, rapidly, and widely. They have a negative effect on native plant communities and wildlife and cost millions of dollars each year to control. $500 million a year is spent on residential invasive weed control and an additional $1 billion invested in invasive weed control on golf courses in the United States (footnote 1). This number does not include the amount spent in natural areas, that number is considerably higher. An example of an out-of-control invasive is purple loosestrife. Originally introduced as an ornamental plant, purple loosestrife now occurs in 48 states, and costs of control total $45 million per year (footnote 2).
Control methods vary from mechanical (physical removal, the introduction of fire or flooding), chemical (using pesticides, herbicides, or fungicides), or biological (introduction of a natural enemy or pest but this cannot be done without continued monitoring of the introduced control). No method is foolproof and the use of millions of pounds of pesticides carries its own risks. Invasive plants are considered second only to habitat loss as a major factor in the decline of native species.
Characteristics of invasive plants:
- Not native to North America
- Ability to spread and mature quickly
- Lack of natural controls
- Often found in disturbed areas like roadsides and fragmented edges
- Adaptable to variable growing conditions
Many invasive plants found in the United States today were introduced as ornamentals for landscaping purposes:
Others were used by the federal government for use as windbreaks and in erosion control:
USDA Forest Service Invasive Species Program is a portal to invasive species information. The goal is to reduce, minimize or eliminate the impact of invasive species. Features a national strategy available for download, species profiles, and links to current news and issues. This website also contains information on invasive insects, diseases, and other problem species now found in the United States.
The National Invasive Species Council is a national initiative to ensure the federal government has programs and activities to prevent and control invasive species. The website features FAQs, links to education and public awareness, research and control methods, restoration of degraded habitats, and much more.
Invasive Plant Atlas of the U.S. is a collaborative project between the National Parks Service and the University of Georgia’s Center for Invasive Species and Ecosystem Health. Displays invasive plants in categories: shrubs, vines, aquatics, trees, flowering plants, etc. making it very easy to find specific plants. Also has an image gallery making identification easier.
Plant Conservation Alliance’s (PCA) Alien Plant Invaders Working Group is a consortium of governmental and non-governmental organizations working to solve problems of native plant conservation. The website features downloadable fact sheets for invasive plants, notes current distribution and effects on ecosystems.
Weeds Gone Wild is a PCA working group. The website includes recipes for invasive plants in cooking, “Least Wanted” fact sheets of major invasive threats, color photos, and distribution maps and publications and articles.
Invasive Plant Atlas of New England (IPANE) is a comprehensive website, including a database of invasive plants found throughout New England, catalog of species, data, images, and distribution maps.
UConn Plant Database provides species lists of plants A-Z, lists invasive tendencies, and species of concern in Connecticut.
Connecticut Invasive Plant Working Group provides information on laws pertaining to the sale, distribution, and use of invasive plants in Connecticut. Provides links to local resources, publications, and a photo gallery. Also has a list of criteria a plant must meet to be considered invasive in Connecticut.
Connecticut Department of Energy and Environmental Protection (CT DEEP) has a list of the general statutes on invasive plants, invasive species identification sheets, and contact information for private landowners seeking to manage invasive species on their property.
- Pimental et al. (2005). “Update on the environmental and economic costs associated with alien species in the United States.” Ecological Economics, 52, pp-273-288.
- ATTRA (1997). Purple loosestrife: Public Enemy #1 on federal lands, ATTRA Interior Helper Internet, Washington D.C.