Species Information

• Iberian starthistle (Iberian knapweed)
• Centaurea iberica Trev. ex Spreng.
• USDA Symbol: CEIB
• Oregon Noxious Weed Designation: A, T
• Pictures

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Identification: Annual or biennial; rosette forms in May and June, blooms midsummer through fall. Grows 1 to 6 feet tall. Plant covered in fine hairs. Leaves divided into narrow linear segments. Rosettes have spines in center. Flower heads are purple with straw-colored spine-like bracts over 1 inch in length. Seeds are plumed, the distinguishing factor between this plant and purple starthistle. This is a rare plant in Oregon, known to occur only in Clackamas County.

Impacts: Closely resembles purple starthistle and both species have the ability to adapt to a variety of climactic conditions. They are extremely competitive along roadsides and in low-rainfall range situations as well as in higher rainfall pastures, where they displace valuable forage species. The sharp spines deter grazing animals, access to livestock and wildlife, reduce the value of hay and can impede recreational use. This weedy plant has the potential to become widely established, having significant impact to agriculture and wildland resources.

Biological Controls: Biological control agents are not used on "A" listed weeds in Oregon. This weed is being managed for eradication or containment.

Oregon Maps of Iberian Starthistle Distribution

Links:

USDA Plants Database information on Iberian starthistle

GRIN Database information on Iberian starthistle

Oregon Department of Agriculture information on Iberian starthistle