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Submodule 1: What are invasive weeds?

What are invasive plants?

When someone mentions the word “weed”, most people know exactly what they mean…a plant that is growing where you don’t want it to grow. Using this definition, any plant could be called a weed, depending on where it is growing. It is estimated that there are about 1,500 “weeds” growing the in U.S. that originated outside the country. A term commonly used by professionals when describing weeds is “invasive plants.” Executive Order 13112, which in 1999 established the National Invasive Species Council (Council), defines an invasive species as one that is:

1) non-native (or alien) to the ecosystem under consideration and

2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

The Council is made up of 13 Departments and Agencies who work together to prevent the introduction of all types of invasive species (including plants, animals, and other organisms such as microbes), to provide for their control, and to minimize the potential economic, ecological, and human health impacts caused by invasive species. Because invasive plant infestations can have such a negative impact on the ecology and economics of an ecosystem, much of the efforts of the Council are directed toward preventing the introduction and establishment of these plants, and controlling invasions once they have occurred.

 

The U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) has established official definitions of “weeds,” “invasive plants,” and other terms used to describe these types of plants. Let’s look at some of these definitions from APHIS and other government sources:

• Invasive plant - A species that demonstrates rapid growth and spread, invades habitats, and displaces other species. Generally, these plants inflict harm to their new environment.
• Weed - any plant that poses a major threat to agriculture and/or natural ecosystems within the United States.
• Alien (or Exotic) plant – a plant introduced and occurring in locations beyond its known historical range. This includes introductions from other continents, bioregions, and also those not native to the local geographic region. For example, a plant native to one region of the U.S. may be considered “alien” in another.
• Non-native plant: a plant found in a particular area of interest that has been artificially brought into the area, usually by human action. Same as Non-indigenous or introduced plant. Note that many non-native plants are not invasive.
• Noxious plant (weed) –Any living stage (including but not limited to seeds and reproductive parts) of any parasitic or other plant of a kind, or subdivision of a kind, which is of foreign origin, is new to or not widely prevalent in the United States, and can directly or indirectly injure crops, other useful plants, livestock, or poultry or other interests of agriculture, including irrigation, or navigation or the fish and wildlife resources of the United States or the public health.

According to Executive Order 13112, a native plant is "a plant that, other than as a result of an introduction, historically occurred or currently occurs in that ecosystem."

 

 

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