Invasive and Noxious Plant Problems

An invasive plant is ” an alien species (non-native) whose introduction does or is likely to cause economic or environmental harm or harm to human health.”

Highly invasive plants that are threats particularly to agricultural production and clog waterways are considered ‘noxious‘.  These plants are highly regulated and are illegal to buy, sell, or grow.

Norway maple (Acer platinoides) an invasive, yet widely popular, street and lawn tree that readily reseeds itself. Photo credit: geneva_wirth Flickr CC BY-NC 2.0
Purple Loostrife (Lythrum salicaria) is considered a noxious weed that invades wetland areas. It is considered invasive in all lower 48 US states. Photo credit: Ron Schott Flickr CC BY-NC-SA 2.0
Burning bush also called Winged euonymus (Euonymus alatus), is considered an invasive shrub in some parts of the US. Photo credit: Susan Buffler
English Ivy (Hedera helix), a noxious weed, takes over a tree in Virginia. Photo credit: Miles Grant Flickr CC BY-NC-ND 2.0

Why are invasive and noxious plants a problem?

According to the United States Forest Service invasive and noxious weeds are a problem for the following reasons:

  • Invasive species have contributed to the decline of 42% of U.S. endangered and threatened species, and for 18% of U.S. endangered or threatened species, invasives are the main cause of their decline.
  • Invasive species compete directly with native species for moisture, sunlight, nutrients, and space.
  • Overall plant diversity can be decreased
  • Establishment and spread of invasive species can degrade wildlife habitat
  • Results in poor quality agriculture lands
  • Degraded water quality
  • Increased soil erosion
  • Decreased recreation opportunities

These impacts change nature’s balance on which all species depend.

Invasive plants were brought to the United States for ornamental reasons, as forage for livestock, and for soil stabilization. Many of these plants arrived accidentally on ships or other means of transport and are spread by people, birds, and other animals accidentally carrying seeds on clothing and fur.

Some Landscape Plants Considered Invasive

We tend to think of invasive plants as undesirable weeds, however, many popular landscape plants are considered invasive.

Some states have made certain landscape plants illegal to sell. For instance, the state of New Hampshire has banned the sale of burning bush, Norway maple, and Japanese barberry.

Some plants may be considered more invasive in some parts of the country than others. For instance, water hyacinth does not survive freezing winters but is invasive in the southern US. Some invasive plants can be controlled with time and effort.

Recommendations

The National Arboretum recommends following these steps to reduce the amount of non-native invasive species in the landscape:

  • Contact your local native plant society or state Department of Natural Resources to find out which plants are invasive in your area
  • Lots of information is available on the Internet
  • Learn to identify locally important invasive plants
  • Remove invasive plants on your property or prevent their spread
  • Only use non-invasive plants when landscaping your property
  • If your property borders a natural area, consider using only native plants in your landscape
  • Find non-invasive or native alternatives for invasive landscape plants
  • Use systemic herbicides carefully as a last resort to remove invasive plants
  • Make others in your neighborhood aware of invasive plants

General Information:

Center for Invasive Plant Management
National Invasive Species Information Center: United States Department of Agriculture National Agricultural Library
National Resource Conservation Service (NRCS)

Additional Resources by Region:

West

Washington: The Myth of Well-Behaved Ornamentals

Northeast

           New York: Alternatives to Ornamental Invasive Plants
Maryland: Invasive Plants  Cause Ecosystem-Level Changes

Midwest

Indiana: State Noxious Weeds List

Southeast

Tennessee: Tennessee’s Native Plant Alternatives to
Exotic Invasives A Garden & Landscape Guide