Yellow Starthistle

Yellow starthistle Centaurea solstitialis L. Sunflower Family
Key identifying traits Bright yellow flower head Sharp spines or thorns ¾"-1" long at base of flower heads Plant grows 2-3 feet tall, has grayish-green foliage and small "wings" on the stems Flower heads are borne singly on ends of branches Old plants or last year’s skeletons have a cottony white tuft where flowers were Seedlings resemble a dandelion with deep lobed leaves Biology and Ecology Annual – reproduces only by seed Invades rangelands, roadsides, and other disturbed areas Thrives in sunny sites – does not tolerate shade Toxic to horses in large amounts Flowers June through October Can have several flushes of plants per year Control Prevention - Learn to identify the plant; know your property; beware of fill dirt, hay and seed from outside your area; confirm identification of any possible sightings Biological – Over the years, several agents have been released in our county; no visible impact to date Cultural – Competitive vegetation helps although plants can invade well managed areas Mechanical – Killed by cultivation and tillage or by pulling; needs to be before bloom or, if after, bag or burn plants in a pile as appropriate; seed bank will be present for years Chemical – Several effective at label rates when applied pre-bud; the addition of 2, 4-D to other herbicides when in early flower will help stop seed production. SCNWCB has had very good results with aminopyralid. Refer to the PNW Weed Management Handbook for specific chemical recommendations	seedling/rosette
	flower head
	plants in field
	winter skeleton
*Where found –* Common in the Gold Hill area near Kettle Falls with smaller infestations found on open south and west slopes elsewhere in Stevens County. MS.doc PDF