Category 1 Noxious Weeds

Category 1 noxious weeds are weeds that are currently established and generally widespread in many counties of the state. Management criteria include awareness and education, containment, and suppression of existing infestations and prevention of new infestations. These weeds are capable of rapid spread and render land unfit or greatly limit beneficial uses.

Canada Thistle	Field Bindweed	Whitetop or Hoary Cress	Russian Knapweed	Spotted Knapweed
Diffuse Knapweed	Dalmatian Toadflax	St. Johnswort	Sulfur Cinquefoil	Common Tansy
Houndstongue	Yellow Toadflax	Leafy Spurge	Oxeye Daisy	Hoary Alyssum

Category 2 Noxious Weeds

Category 2 noxious weeds have recently been introduced into the state or are rapidly spreading from their current infestation sites. These weeds are capable of rapid spread and invasion of lands, rendering lands unfit for beneficial uses. Management criteria includes awareness and education, monitoring and containment of known infestations and eradication where possible.

Rush Skeletonweed			Purple Loosestrife	Tansy Ragwort	Meadow Hawkweed Complex	Orange Hawkweed
Tall Buttercup			Tamarisk (Saltcedar)	Perennial Pepperweed	Yellow Flag Iris	Blueweed

Category 3 Noxious Weeds

Category 3 noxious weeds have not been detected in the state or may be found only in small, scattered, localized infestations. Management criteria include awareness and education, early detection and immediate action to eradicate infestations. These weeds are known pests in nearby states and are capable of rapid spread and render land unfit for beneficial uses.

Yellow Starthistle	Common Crupina	Eurasian Watermilfoil	Dyers Woad	Flowering Rush
Japanese Knotweed  Complex

Category 4

Category 4 noxious weeds are invasive plants and may cause significant economic or environmental impactes if allowed to become established in Montana.  Managment criteria included prohibition from sale by the nursery trade.  Reaserch and monitoring may result in the plant being listed in a different category.

Scotch Broom