Cotton thistle is native to Europe and Western Asia, and invasive in many other parts of the world. It is a biennial plant, producing a large rosette of spiny leaves in the first year. In the second year, the plant can grow to as much as 3 m tall. The large, deeply lobed leaves are spiny, and often covered with white woolly hairs; they give the plant a greyish appearance. The massive main stem may be 10 cm wide at the base and branched in the upper part.
The flower buds form first at the tip of the stem and later at the tip of the axillary branches. The flowers are globe shaped, 2 to 6 cm in diameter, from dark pink to lavender. They are highly attractive to pollinating insects such as bees and butterflies. After flowering, the ovary starts swelling and forms up to 40,000 seeds per plant.