Italian Thistle

Italian thistle is an annual to biennial invasive thistle native to the Mediterranean region and now widespread in parts of western North America, including Oregon and California. It typically invades disturbed sites, pastures, open grasslands, and roadsides, where it forms dense, spiny stands that suppress native vegetation and reduce forage quality for livestock and wildlife. The plant produces numerous pink to purple flower heads with sharp bracts and spiny, deeply lobed leaves. Italian thistle spreads exclusively by seed, which can be carried by wind, animals, or vehicles, allowing it to rapidly colonize new areas and persist without consistent management. Cobwebby hairs cover stems and the undersides of leaves, with spiny wings on the stems. The leaves are deeply incised with a slightly woolly undersurface. Small purple to pink flowers are borne singly or in clusters.