bull thistle

Cirsium vulgare (Savi) Ten.

U.S. Nativity: Exotic
Habit: Herb

Synonym(s): common thistle, spear thistle

Cirsium vulgare is an annual or biennial, herbaceous plant that invades disturbed areas throughout the United States. The spiny, spreading, winged stems are up to 7 ft. (2.1 m) tall.
Leaves are 3-12 in. (7.6-30.5 cm) long, lance-shaped and very hairy.
Flowers develop, at the apex of the plant, from June to September. The purple flower heads are 1.5-2 in. (3.8-5.1 cm) in diameter and 1-2 in. (2.5-5.1 cm) long with narrow, spine-tipped bracts.
Fruits have several bristles on the tip and are up to 0.2 in. (5 mm) long.
Ecological Threat
Cirsium vulgare can invade almost any type of disturbed area, such as forest clearcuts, riparian areas and pastures. Plants can form dense thickets, displacing other vegetation. The spiny nature of the plant renders it unpalatable to wildlife and livestock and reduces the forage potential of pastures. Cirsium vulgare is native to Europe, western Asia, and northern Africa. It is thought to have been introduced to the eastern United States during colonial times and the western United States in the late 1800s. It is currently found in all 50 states.

Identification, Biology, Control and Management Resources

Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
Fire Effects Information System - USDA Forest Service
Weed of the Week - USDA Forest Service
Weed Field Guide - USDA Forest Service