Yellow Startthistle

QUICK IDENTIFICATION

  • Whitish hairs on leaves; upper leaves appear winged
  • Sharp spines below yellow flower head up to 1 inch long
  • Yellow flowers similar to spotted knapweed flowers
  • Height 3 to 5 feet

Video Information


Weed Pictures



Weed Information


Type Information
Toxicity Toxic. Horses.
Control Biological, hand pulling/digging, herbicide and mowing. Contact your County Weed District or local applicator for more information.
Habitat Grassland, rangeland, pastures, cultivated fields, disturbed sites and roadsides
Root Large taproot that grows to soil depths of 3 to 5 feet.
Leaf Shape Deeply lobed rosette leaves and becomes leaves become linear as plant matures
Lifespan Winter annual; one year life cycle; may germinate in fall or spring.
Priority 1A Weed Not present or limited presence in Montana. If you think you’ve found this plant, please contact your county weed coordinator or Montana Department of Agriculture immediately!
Similar Looking Plants At rosette stage it resembles other knapweeds.
Important Information Yellow starthistle spreads primarily by seed dispersal and seeds remain viable in the soil for up to 10 years. It causes chewing disease in horses and has been known to puncture car tires.
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