Need Help Identifying a Weed?
Proper identification is important before attempting control. Many plants can appear similar, especially at different stages of growth.
- Take clear photos of the entire plant, leaves, and flowers
- Note the location and growing conditions
- Contact the Flathead County Weed Control District for assistance
Selected high-priority weeds may include detailed identification pages as they become available.
Priority 1A — Not Yet Established or Limited Presence
These weeds are not currently established in Montana or are present in very limited areas. Management focuses on early detection and rapid response, with the goal of eradication.
- Yellow starthistle (Centaurea solstitialis)
- Dyer’s woad (Isatis tinctoria)
- Common reed (Phragmites australis ssp. australis)
- Medusahead (Taeniatherum caput-medusae)
- Rush skeletonweed (Chondrilla juncea)
Priority 1B — Limited Distribution
These weeds are present in Montana but occur in limited areas. Management focuses on containment, control, and preventing further spread.
- Leafy Spurge (Euphorbia esula)
- Spotted Knapweed (Centaurea stoebe)
- Diffuse Knapweed (Centaurea diffusa)
- Russian Knapweed (Rhaponticum repens)
- Dalmatian Toadflax (Linaria dalmatica)
- Yellow Toadflax (Linaria vulgaris)
- Houndstongue (Cynoglossum officinale)
- Oxeye Daisy (Leucanthemum vulgare)
- Canada Thistle (Cirsium arvense)
- Field Bindweed (Convolvulus arvensis)
- St. Johnswort (Hypericum perforatum)
- Sulfur Cinquefoil (Potentilla recta)
Priority 2A — Common in Isolated Areas
These weeds are common in isolated areas of Montana. Management focuses on eradication or containment where infestations are less abundant, with local weed districts prioritizing response based on local conditions.
- Tansy ragwort (Senecio jacobaea)
- Meadow hawkweed complex (Hieracium spp.)
- Orange hawkweed (Hieracium aurantiacum)
- Tall buttercup (Ranunculus acris)
- Perennial pepperweed (Lepidium latifolium)
- Yellowflag iris (Iris pseudacorus)
- Eurasian watermilfoil (Myriophyllum spicatum; Myriophyllum spicatum × Myriophyllum sibiricum)
- Flowering rush (Butomus umbellatus)
- Common buckthorn (Rhamnus cathartica)
- Ventanata (Ventanata dubia)
Priority 2B — Abundant and Widespread
These weeds are abundant and widespread in many Montana counties. Management focuses on eradication or containment where infestations are less abundant, with local weed districts prioritizing response based on local conditions.
- Canada thistle (Cirsium arvense)
- Field bindweed (Convolvulus arvensis)
- Leafy spurge (Euphorbia esula)
- Whitetop (Cardaria draba)
- Russian knapweed (Centaurea repens)
- Spotted knapweed (Centaurea stoebe or C. maculosa)
- Diffuse knapweed (Centaurea diffusa)
- Dalmatian toadflax (Linaria dalmatica)
- St. Johnswort (Hypericum perforatum)
- Sulfur cinquefoil (Potentilla recta)
- Common tansy (Tanacetum vulgare)
- Oxeye daisy (Chrysanthemum leucanthemum or Leucanthemum vulgare)
- Houndstongue (Cynoglossum officinale)
- Yellow toadflax (Linaria vulgaris)
- Saltcedar (Tamarix spp.)
- Curlyleaf pondweed (Potamogeton crispus)
- Hoary alyssum (Berteroa incana)
Priority 3 — Regulated Plants
These plants are not listed as noxious weeds statewide, but are regulated to prevent their spread or introduction into Montana.
Management requirements may vary depending on species and location. These plants are typically monitored to limit distribution and reduce potential impacts.
- Cheatgrass (Bromus tectorum)
- Hydrilla (Hydrilla verticillata)
- Russian olive (Elaeagnus angustifolia)
- Brazilian waterweed (Egeria densa)
- Parrot feather watermilfoil (Myriophyllum aquaticum or M. brasiliense)