Carduus nutans is an herbaceous, biennial plant that grows to 6 ft. (1.8 m) tall. The stem has very spiny wings. Carduus species may hybridize with each other.
Foliage
Leaves are green and lanceolate to oblong-lanceolate. They are often pinnatifid and are very prickly. Leaves are usually sessile to slightly clasping. Basal leaves are 4-16 in. (10-40 cm) long. Leaf characteristics are variable across different varieties and subspecies.
Flowers
Showy, solitary, hemispherical, red to purple, disk flowers bloom from June to September. Phyllaries are spinetipped and overlap with several rows.
Fruit
Fruits are small achenes, 1.52 in. (45 mm) long, about 0.04 in. (1 mm) in diameter, including a white to light brown pappus. The seeds have longitudinal dotted stripes.
Ecological Threat
Carduus nutans invades a variety of disturbed areas. Pastures are particularly at risk because It is unpalatable to livestock. Once established it can spread rapidly due to high seed production (as much as 120,000 seed per plant). Carduus nutans is native to Western Europe and was accidentally introduced into the United States in the early 1900s.