Cotton thistle

Onopordum acanthium, the cotton thistle or Scotch thistle, is a robust biennial in the family Asteraceae. In its first season it forms a large rosette of spiny grey-green leaves; in the second year it bolts to a stout stem 1–3 m tall, conspicuously spiny-winged 2–3 cm wide along its length and densely clothed, like the foliage, with cottony white woolly hairs that give the whole plant a pale, greyish aspect. The alternate cauline leaves are 10–50 cm long, deeply lobed and stiffly spine-margined. From summer into early autumn it bears solitary or clustered globe-shaped capitula 2–6 cm across with dark pink to lavender disc florets, followed by smooth 3 mm achenes bearing a pappus of slender bristles; a single plant may produce 8,400 to 40,000 seeds. Native to Europe and western Asia from Iberia to Kazakhstan, it thrives on disturbed, sandy or calcareous, nitrogen-rich soils along roadsides, fields and riverbanks.