What is a Noxious Weed?
Noxious weeds are defined as being any exotic plant species which may render land unfit for agriculture, forestry, livestock, wildlife or other beneficial uses or that may harm native plant communities.

Montana Priority 1A Weeds:
These species are not present, or have very limited presence in Montana.  State management criteria requires eradication if detected, as well as education and prevention efforts. To date, dyer's woad is the only Priority 1A species present in Missoula County.

Montana Priority 1B Weeds:
These species have a limited presence in Montana. Management criteria requires eradication if detected, as well as education and prevention efforts. Missoula County has limited infestation of blueweed, rush skeletonweed, purple loosestrife and knotweed complex.

Montana Priority 2A Weeds:
These species are common in isolated regions of Montana.  Management criteria requires eradication or containment where they are less abundant.  Management of these species are prioritized by the local county weed district. Missoula County has populations and places major emphasis on the management of orange hawkweed, perennial pepperweed, yellowflag iris and common buckthorn.

Montana Priority 2B Weeds:
These species are abundant in Montana and widespread in many counties. Management criteria requires eradication or containment where less abundant.  Management of these species are prioritized by the local county weed district.  Management of these species in Missoula County occurs through Cooperative Weed Management Areas and cost-share grants with local landowners.  There are also strong biological control systems established for leafy spurge, spotted and diffuse knapweeds and Dalmatian and yellow toadflax.