Kootenai County Seal, Administration Building, and Lake
  

Bill Hargrave,
Weed Superintendent

Email: kcnoxiousweeds@kcgov.us
P: (208) 446-1290
F: (208) 446-1282

Physical Address:
Click here for map.
10905 N. Ramsey Road
Hayden, ID 83835

Office Hours:
Mon - Fri 8:00a.m. - 4:30p.m.

YELLOW STARTHISTLE


BOTANICAL NAME: Centaurea solstitalis

WHAT DOES IT LOOK LIKE? Yellow Starthistle is a winter annual. Its seeds germinate in the fall, overwinter as a rosette, continue to grow in the spring, and then die before winter. It can grow from 1 to 4 feet tall depending upon growing conditions. The more rainfall, the taller the plants will grow and the more seeds they will produce. In May and June the flower stalk begins to form. Flower heads are yellow with cream colored thorns, one-quarter to three-quarter inches long, sticking out from the flowering heads.

WHERE DOES IT GROW? It grows well on dry sites in rangeland, roadsides, and waste areas.


WHEN DOES IT BLOOM?" Mid July to early August bright yellow flowers appear. plants begin to dry in August and become easily identifiable skeletons that are silvery gray with a white cottony flowerhead.

HOW DOES IT SPREAD? Yellow starthistle produces two types of seeds: plumed and plumeless. The plumed seeds are caught and spread by the wind. The plumeless seeds drop to the ground once the seed head starts to fall apart.

HOW DO I CONTROL IT? Learn to identify this weed. As with all annual weeds, keeping them from going to seed is the best control.


CONTROL METHODS

NON-CHEMICAL
- Small infestations can be controlled by hoeing or hand pulling.
- Frequent cultivation is an excellent means of removing young plants.
- Proper grazing management will limit yellow starthistle invasions.
- Horses must not graze in pastures with yellow starthistle. If eaten in large quantities, horses will develop a fatal nervous disease called "Chewing Disease". This plant is not toxic to sheep, goats or cattle.
- Six biocontrol agents, three beetles and three flies , have been released in heavily infested areas of Washington and Idaho.

CHEMICAL
Yellow starthistle in the rosette stage is not difficult to control with herbicides. As it reaches the flowering and seed making stage it becomes resistant to chemical control.


WANT TO KNOW MORE?

Call the Kootenai County Noxious Weed Control Office at (208)446-1290 or visit our office at 10905 Ramsey Road in Hayden. Email us at kcnoxiousweeds@kcgov.us

SOURCES
- Biology and Biological Control of Yellow Starthistle by L. Wilson, C. Jette, J. Connett, J. McCaffrey, 2nd Edition, 2003
- Washington Weed Board website http://www.nwcb.wa.gov
- Controlling Yellow Starthistle, Council of Bay Area Resource Conservation Districts publication Number 6, June 2000


Download a PDF
Yellow starthistle (62.92 KB)
Information to identify and control yellow starthistle a noxious weed in Idaho.