Yellow Starthistle (Centaurea solstitialis)

Status:

Listed Noxious Weed In Montana & North Dakota

History:

First Montana Specimen Collected 1

County:

Missoula

Year:

1936

“Yellow starthistle is thought to have originated along the Mediterranean Coast and has spread throughout Europe as far as the Asian steppes. Yellow starthistle was first reported growing on ballast grounds near western seaports. Early California records indicate C. solstitialis at Oakland in 1869 and Vacaville in 1887. By 1965, the California Department of Food and Agriculture estimated 1.9 million acres were infested.

By the 1920's it was widely distributed in Eastern Washington. It has spread as far north as Stevens County. An outbreak in Okanogan from certified but contaminated seed occurred following seeding after a fire.” (WWCB)

Habitat:

Growth Habit:

Annual, erect, rigid branching stems.

Leaves:

Basal leaves deeply lobed upper leaves not lobed, small, sharply pointed.

Stem:

Rigid, covered with a cottony fiber, to 30 inches tall, winged structures.

Flower:

Yellow, terminal, flower bracts are tipped with straw-colored, ¾ inch thorn.

Roots:

Taproot.

Seeds:

Smooth, light-colored, often darker mottled, 1/8 inch long, notched just above the
base.

Other Notes:

Currently no known infestations in the Yellowstone River corridor.