The Mission of the Yellowstone County Weed Department is to assist the public, private, and other government agencies to manage and control existing noxious weed infestations as well as to prevent new invasive species from infesting Yellowstone County.

Yellow StarthistleCentaurea solstitialis L.

Sunflower family - Asteraceae

Photo from Weeds of the West, revised edition.

Toxic

Rosette

Stem

Leaf

Bloom

Plant

Photos from Montana Weed Control Association

Video Supplied By Ravalli County Weed District

Attribute	Description
Toxicity	To Horses.
Growth Habit	Annual, erect, rigid brancing stems.
Leaves	Basal leaves deeply lobed, upper leaves not lobed, small, sharply pointed.
Stem	Rigid, covered with a cottony fiber, to 30" tall, winged structures.
Flower	Yellow, terminal, flower bracts are tipped with straw-colored, 3/4 inch thorn.
Roots	Taproot.
Seeds	Smooth, light-colored, often darker mottled, 1/8 inch long, notched just above base.
Reproduction	Seeds.
Habitat	Rangelands, pastures, vineyards, abandoned croplands, alfalfa and small grain fields and roadsides.
Biological Controls	Seed head fly (Terellia uncinata).
Herbicides	None used in Yellowstone County at this time.