Appearance Arctium minus grows up to 6 ft. (1.8 m) tall. It is a biennial forb that occurs throughout the United States. First year plants form large rosettes. A stout flowering stalk is formed in the second year. Foliage Stem leaves are large, heart-shaped and very hairy on the undersides. Basal leaves are dark green, heart-shaped and up to 1 ft. (0.3 m) long. Flowers Flowering occurs in July to October, when pink to purple flowers develop. Flowers are enclosed in a prickly bur. Fruit One plant typically produces 15,000 seeds. It reproduces by seeds. Ecological Threat Arctium minus can become a problematic invader of pastures, hay fields and open prairie ecosystems. It acts as a secondary host for pathogens, such as powdery mildew and root rot, which affect economically important plants. Arctium minus is native to Europe and came to the United States via accidental introduction. Indirectly affects the development of economically important plants by hosting powdery mildew and root rot. Reduces the value of sheep’s wool due to the seed heads entangling in it. It is responsible for tainting milk products if grazed in large quantities.