Onopordum acanthium (cotton thistle)

Cotton thistle leaves

The leaves of cotton thistle (Onopordum acanthium) are covered with fine white hairs that give them a silvery sheen. This felt-like pubescence may serve as protection against the hot sun or desiccation.

Cotton thistle leaf

Habitus & biology

Onopordum acanthium is a biennial. After the seeds germinate in late summer or fall, a rosette of basal leaves first appears. Only after overwintering does it grow upwards and can reach a height of up to two meters.

The basal leaves wither before the flowers open. Once the seeds are ripe, the rest of the plant dies.

Onopordum acanthium by the wayside
Onopordum acanthium by the wayside, the basal leaves are already withered.

The flowering period of the cotton thistle can last from June to August.

Cotton thistles by the wayside
Cotton thistles by the wayside, found at the beginning of May.

Origin & habitats

The native range is Eurasia and North Africa. As an introduced species, it is also found in some regions of Australia, North America and South America (source).

Flowering cotton thistles on a dam
Flowering cotton thistles on a dam.

Onopordum acanthium grows along roadsides, embankments, meadows, and quarries and does best in warm, sunny places.

Onopordum acanthium cotton thistle


The cotton thistle belongs to the Daisy family (Asteraceae) and is closely related to the artichokes. Onopordum acanthium is also known colloquially as Scotch thistle or Scottish thistle.

The leaves of the cotton thistle are covered with tomentose hairs
The leaves of the cotton thistle are covered with tomentose hairs.