What are Invasive Plant Species, Anyway?

Why do we need a definition? Because we nationally need to "pull together" and one accepted definition will allow us to do that smoothly. Let's begin by calling them weeds. Everyone has a definition for a weed similar to a plant out of place. With this definition we call a dandelion in your front yard, a weed. Beyond this simplistic definition most States have defined noxious weed lists.

Pick out the purple loosestrife in this bouquet of invasive plants.

A noxious weed is one that has been determined by the State to be detrimental to agriculture, your health, or the environment. If your State has purple loosestrife on their list, that means the State could fine you if you do not remove it.

An invasive plant species is certainly a weed, not only out of place, but out of its country or region of origin. It is an introduced plant species that is aggressive. The Norway maple in your yard would fit this definition. It might or might not be on your State's noxious weed list. Kudzu, knapweed, star thistle, and mile-a-minute vine fit also. The definition used by the Executive Order 13112 is "an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health."

No sweat, you say! Then legally I do not have to do anything about an invasive plant species. Wrong. Any State Department of Transportation who uses federal funding, must avoid the planting of "known invasives" (State noxious weeds) or lose funding. Also each DOT must include an analysis of invasive species and future management on any new project during the NEPA process. If you care about the future value of your neighborhood, your local nature preserve or park, wildlife habitat, biodiversity or any other environmental or esthetic characteristic that adds up to your quality of life, you also care about invasive species!

The impacts of invasive species, plants and animals alike, which leave their competition behind in their place of origin, tend to outcompete native plants where lands have been disturbed. When they displace native plants and animals they lower diversity, reduce hunting and fishing potential, change the aesthetics of a habitat, lower the value of recreational and agricultural property, crowd out endangered species, replace forage value, diminish wild rice crops/forest crops, and on it goes.

Invasive Species means different things to many people

Plants known as undesirable, exotic, alien, weed, pest, opportunist, biological wildfire, nonnative, nonindigenous, and biological pollution, are terms used over the years. We now call them invasive plant species. They are introduced from another country or region of our own country, leaving behind their competition and displacing vegetation known to exist before European settlement. The Australian native tree, Melalouca has become a pest plant in Florida. The United States native tree, Black locust has become an invasive in Germany. There are many such examples. Black locust has become a weed in regions of the U.S. to which it is not native (the southeast Appalachians region is its origin). Improved global mobility in general increases the risk of unwanted plants.