Most widespread thistle. Biennial.
Has a branched stout stem, which rises in October from a rosette grown the previous season. Plants are short and spindly on poor ground but grow to a height of 1 m in good conditions. Flowers are purple but bluer than nodding thistle.
Scotch thistles often grow after fire or soil disturbance. They can be abundant in pasture as stock, especially sheep, seldom eat them.