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Weed Identification in Christmas Trees

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Bull thistle - Cirsium vulgare (Savi) Tenore
Home > bull thistle
Life cycle: Erect, spiny biennial.

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.

Stems: Spiny-winged, hairy stems elongate during the second year, often branched up to 7 feet tall.

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.
Bull thistle flower Bull thistle seedling
Bull thistle flower head. Bull thistle seedling.
Bull thistle rosette
Bull thistle rosette.
Bull thistle leaf surface
Coarse hairs on the upper leaf surface of bull thistle.
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.
Canada thistle flower Canada thistle plant Canada thistle mature flower heads
Canada thistle flower head. Canada thistle plant. Canada thistle mature flower heads.
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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02/07/08