Bull thistle – Cirsium vulgare
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EmailCirsium vulgare (Savi) Tenore
Asteraceae (Aster family)
MI Status
Non-native
Life cycle
Erect, spiny biennial.
Leaves
First-year leaves originate from a basal rosette, followed by an erect, branched, flowering stem in the second year. Seedlings have egg- to spatula-shaped cotyledons and oval, oblong to spatula-shaped leaves with bumpy surfaces and marginal spines. Mature leaves are alternate, lance-shaped, deeply cut or lobed, with long, stiff spines. Leaves have coarse hairs above and soft, cottony hairs below.
Stems
Spiny-winged, hairy stems elongate during the second year, often branched up to 7 feet tall.
Flowers and fruit
Red to purple solitary flower head composed entirely of disk flowers, 1–2 inches wide, surrounded by spiny bracts. Seeds are produced in single‑seeded, chili‑pepper‑shaped fruits adapted for wind dispersal.
Reproduction
Seeds.
Similar weeds
Canada thistle [C. arvense (L.) Scop.]
Differs by having a prolific, patch-forming perennial nature with a deep, creeping root system; leaves with smooth, dark green upper leaf surfaces and irregularly lobed to crinkled, spiny margins; and smaller (less than 1 inch wide) pink to purple flower heads with spineless bracts.
