Invasive Weeds

What is an invasive weed?

Invasive weeds are plants that have been introduced into an environment outside of their native range. In their new environment, they have few or no natural enemies to limit their reproduction and spread (Anonymous 2002). Invasive weeds affect us all— farmers, homeowners, taxpayers, consumers, and tourists.

Several invasive weeds also are considered noxious weeds. Noxious weeds are nonnative plants that have been legally designated as serious pests because they cause economic loss or harm the environment. Oregon, Washington, and Idaho each has a state-designated noxious weed list that changes over time as weed invasions occur. Some, but not all, of the currently designated noxious weeds are included in this publication.

Why should we care about invasive weeds?

  • Invasive weeds reduce land values.
  • Invasive weeds reduce crop yield and quality.
  • Invasive weeds cause fire hazards.
  • Invasive weeds impede water flow, reduce water availability, and increase soil erosion.
  • Some invasive weeds are toxic to animals and humans.
  • Invasive weeds reduce biodiversity and displace native plant and wildlife species.