Overview
Cirsium vulgare is a coarse, spiny biennial in the daisy family (Asteraceae) reaching 24–72 inches (60–180 cm) tall with an 18–36 inch (45–90 cm) spread. First-year plants form a large, flat rosette of deeply lobed, spiny leaves 6–15 inches (15–38 cm) long, dark green and rough-prickly above, gray-woolly beneath. Second-year stems are erect, branching, and conspicuously winged by decurrent leaf bases with stiff, yellow-tipped spines along the wings. Flower heads are solitary or clustered at branch tips, 1.5–2 inches (4–5 cm) in diameter, with purple to magenta tubular florets emerging from a spiny, cobwebby involucre. Pappus bristles are feathery (plumose), distinguishing Cirsium from Carduus (simple bristles). Each plant produces 4,000–10,000 seeds that disperse by wind. Seeds remain viable in soil for 3–5 years. Plants develop a fleshy taproot in the first year, reaching 12–28 inches (30–70 cm) in depth. Unlike C. arvense, bull thistle does not spread by creeping lateral roots and is strictly seed-dependent for reproduction. Listed as a noxious weed in multiple U.S. states. Dense infestations form in overgrazed pastures, clearcuts, and disturbed roadsides.
Native Range
Native to Europe, western Asia, and northern Africa, occurring in meadows, roadsides, pastures, and forest clearings from sea level to approximately 7,500 feet (2,300 m). Introduced to North America, Australia, and New Zealand. Naturalized across all 50 U.S. states and all Canadian provinces.Suggested Uses
Used in weed identification training for differentiating thistle genera (Cirsium versus Carduus versus Centaurea) based on pappus type and stem wing characters. Studied in rangeland management and biological control ecology. Seeds are an important food source for goldfinches. Flower heads visited by bumblebees and painted lady butterflies.How to Identify
Appearance
Size & Dimensions
Height2' - 6'
Width/Spread1'6" - 3'
Bloom Information
Flowers from June through September in the second year. Individual flower heads bloom for 5–8 days. Flowering progresses from the terminal head downward over 6–8 weeks. In the Pacific Northwest, peak flowering occurs in July through August. Seeds mature 2–3 weeks after pollination and disperse by wind via the plumose pappus. Pollinated by bumblebees, butterflies, and hummingbirds.Detailed Descriptions
Flower Description
Purple to magentaFoliage Description
Dark green above, gray-woolly beneath; deeply lobed with stiff yellow-tipped spines; upper leaf surface rough and pricklyGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight