Marsh thistle is a large herbaceous biennial or perennial plant with very narrow spiky leaves. The stalk is reddish, prickly and can grow up to two metres high. Its small purplish red flowers are 1 - 2 cm wide and grow in clusters. The flowers bloom in late summer from July till September.

Marsh thistle grows in spring grove- and peat-like forests, in fen-like peat forests, damp meadows, near brooks and in coastal meadows. The species can also be found on farmlands, field edges and in ditches. Its range extends to Europe and Russia.

Prickly marsh thistle protects its precious interior with its harsh exterior: peeling the stalk reveals an asparagus-like delicacy. The marsh thistle can be confused with the curly plumeless thistle (Carduus crispus).

Marsh thistle grows on pastures, where horses and cows feed on it despite its spikes. Many butterflies’ larvae also feed on the marsh thistle.