Bull thistle – Cirsium vulgare

Bull thistle flower

Bull thistle flower

Bull thistle leaf

Bull thistle leaf

Bull thistle leaf surface

Bull thistle leaf surface

Bull thistle rosette

Bull thistle rosette

Bull thistle seedling

Bull thistle seedling

Bull thistle

Cirsium vulgare (Savi) Tenore
Asteraceae (Aster family)

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, usually solitary flower heads consisting of only disk flowers are 1 to 2 inches wide and encircled by spine-tipped bracts. The seed is enclosed in a single-seeded, chili- pepper-shaped, wind-disseminated fruit.

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.