Idaho OnePlan recommends the website of the Idaho Weed Awareness Campaign as the best resource for up-to-date information about Idaho's noxious weeds, and their control.

We are maintaining this online version of Idaho's Noxious Weeds, by Robert H. Callihan and Timothy W. Miller; revised by Don Morishita and Larry Lass (1999, copyright notice below). The U of I Extension now has a 4th Edition, which contains the currently designated 57 noxious weed species.


Idaho has about 800 of the nations 2,000 weed species, most of which are alien to the state. Idaho's noxious weeds have been introduced from other regions. We do not have the natural systems to keep them in check. Importing natural controls is not possible for all weeds, and it takes decades to and vast resources to introduce naturals controls. As a result, noxious weeds overwhelm native plant communities and disturbed areas, spreading steadily year by year.

Prevention and inspection are the most economical management system for reducing the rate of noxious weed spread. Once noxious weeds have become established expect to spend $30 to $70 per acre for management on your land or in higher taxes for their management on public land.

What is a noxious weed?

Noxious weeds are plant species that have been designated "noxious" by law. The word "noxious" simply means deleterious, and all listed weeds are deleterious by definition. There are hundreds of weed species in Idaho; in 1977, 35 were designated noxious by Idaho law. [As of 2009, there are 57 noxious weed species.] The Idaho Department of Agriculture uses the following criteria for designation of a noxious weed:

  1. It must be present in but not native to Idaho;
  2. It must be potentially more harmful than beneficial to Idaho;
  3. Eradication must be economically physically feasible;
  4. The potential adverse impact of the weed must exceed the cost of control.

Reducing the Spread of Noxious Weeds

Here are a few guidelines to help lessen the spread of noxious weeds in Idaho.