Noxious Weeds

Northwest Regional Resource Conservation and Development

Spotted Knapweed

Early detection and a fast treatment program can save landowners a lot of time and money. Montana state law requires land owners to control noxious weeds on their property.
What are noxious weeds? Any exotic plant species established or that may be introduced in the state that may render land unfit for agriculture, forestry, livestock, wildlife or other beneficial uses or that may harm native plant communities and that is designated by the Montana Department of Agriculture or by the local county weed district. Some negative effects of weeds include: loss of wildlife habitat, reduce livestock grazing capacity, increased soil erosion, and reduced cropland production.

What weed species are declared as noxious weeds?

• Category 1

  These noxious weeds are currently established and generally widespread:
  

  Canada Thistle Russian Knapweed Dalmatian Toadflax Hounds Tongue Oxeye Daisy

  Field Bindweed Spotted Knapweed St. Johnswort Yellow Toadflax Hoary Alyssum

  Hoary Cress Diffuse Knapweed Sulfur Cinquefoil Leafy Spurge

• Category 2

  These noxious weeds have been recently introduced and are spreading rapidly:
  

  Rush Skeletonweed Orange Hawkweed Blueweed

  Purple Loosestrife Tall Buttercup Yellow flag iris

  Tansy Ragwort Tamaris (saltceder) Perennial Pepperweed

• Category 3

  These noxious weeds have been detected and generally only localize infestations:
  

  Yellow Starthistle Dyers Woad

  Purple Loosestrife Flowing Rush

  Eurasian Watermilfoil Japanese Knotweed Complex

• Category 4

  This weed is an invasive plant and may cause significant impacts if it becomes established:
  

  Scotch Broom

To identify these noxious weeds, go to the following web site: www.mtweed.org/identifyingWeeds.html