Yellow starthistle
Centaurea solstitialis

• Yellow starthistle is an annual knapweed from Europe. Populations have existed for several years south of Lewiston. Recently infestations have been found as far north as Coeur d'Alene, Idaho. Overgrazed ranges, abandoned fields, rights-of-way, waste areas, and similar sites are candidates for invasion. It is on the Idaho State Noxious Weed List.
• Plants grow from 2 to 72 inches. Basal leaves form a rosette. Small leaves attach directly to the stem with a wing extension down the side of the stem. Yellow flower heads develop at tips of branched stems. Bracts surround the base of egg-shaped seed heads. The middle and lower bracts have thorns that are 3/4 inch long, stiff and sharp pointed. Seeds develop with plumes for wind dispersal and some are plumeless to scatter when the seedhead breaks up.
• This weed causes "chewing disease" and death in horses.
• Biological agents are available to aid in control of this weed.

Report Sightings of Noxious Weeds

Contact:
Kim Pierson, USFS Botanist
208-737-3212
kpierson@fs.fed.us

• Drive only on established roads and trails away from weed infested areas.
• When using pack animals, carry only feed that is certified weed free.
• Removed weed seeds from pack animals.
• Don't pick the flowers of noxious weeds and take them home.
• Don't pick and transport wild flowers that you can't identify.
• Don't camp or drive in weed infested areas.

Weed Removal Instructions

No Flowers or Seed Present:
Pull the weed and leave it on the area.

Flowers or seed present on the weed:
Pull the weed. Be careful the seed does not fall from the weed. Place the weed in a plastic bag or similar container.

Dispose of the weed by burning or turn it in at a Ranger Station.