Scotch thistle USDA PLANTS SYMBOL: ONAC
Onopordum acanthium L.
Synonym(s): Scottish thistle, cotton thistle, heraldic thistle, Scotch cottonthistle

Scottish thistle is a biennial herb native to Eurasia. Plants can grow up to 8 ft. (2.4 m) tall and 6 ft. (1.8 m) wide. Stems are up to 4 in. (10.2 cm) wide at the base and are marked by prominent, spiny wings along the entire length. Leaves are broadly elliptic, 3.9-19.7 in. (10-50 cm) long, up to 12 in. (30.5 cm) wide with margins marked by large spines. Flowering occurs from July to September, when flowers develop in globe shaped flower heads. Flower heads are purple and up to 2 in. (5.1 cm) in diameter. Fruits are 0.2 in. (4-5 mm) long, smooth achenes. Scotch thistle occurs along roadsides, in fields, pastures, rangelands, riparian areas and other disturbed sites with high soil moisture.

Identification, Biology, Control and Management Resources