Invasive Exotic Plants
Organisms are considered exotic 
when they occur artificially in locations beyond their known historical natural ranges. Species exotic to the U.S. include those transported from Europe, Asia, Africa, South America, Australia and other parts of the world. It also includes any species moved by people from one locality in the U.S. to a new one. For example, black locust (Robinia pseudoacacia) is native to the southern Appalachian region of the eastern U.S. Because of its rapid growth and hardiness, it was planted all around the U.S. during this century for living fences, erosion control, wind breaks and other purposes.
European settlers brought hundreds of plants to North America from their home lands, for food, medicinal, ornamental, and other purposes. Introductions of exotic plants continue today, and are increasing due to increased international travel and trade. Many introduced plants have become naturalized across the continent and some are replacing North American native plant species.
Exotic species are invasive if they display rapid growth and spread, allowing it to establish over large areas. Free from the vast and complex array of natural controls present in their native lands, including herbivores, parasites, and diseases, exotic plants may experience rapid and unrestricted growth in new environments. Invasiveness is enhanced by features such as strong vegetative growth, abundant seed production, high seed germination rate, long-lived seeds, and rapid maturation to a sexually reproductive (seed-producing) stage. Invasive plants reproduce rapidly, either vegetatively or by seed. Their phenomenal growth allows them to overwhelm and displace existing vegetation and form dense one-species stands.
Invasive exotic organisms are one of the greatest threats to the natural ecosystems of the U.S. These unwelcome plants, insects and other organisms are disrupting the ecology of natural ecosystems, displacing native plant and animal species, and degrading our nation's unique and diverse biological resources. Aggressive invaders reduce the amount of light, water, nutrients and space available to native species, alter hydrological patterns, soil chemistry, moisture-holding capacity, and erodibility, and change fire regimes.
- Excerpted from the National Park Service's Weeds Gone Wild website. Visit their website for additional background information.
New Hampshire regulates selected exotic organisms. For more information on state rules and legislation pertaining to exotic species, visit the New Hampshire Invasive Species Program.
Following is a list of some of the invasive exotic plants regulated by the state of New Hampshire. The links will take you to the Invasive Plant Atlas of New England profile for that species.
For more information on invasive exotic plants in New England including additional fact sheets visit the Invasive Plant Atlas of New England.
For invasive exotic plant control information, visit the Nature Conservancy's Invasives on the Web website.
