Northern Prairie Wildlife Research Center
Southern Wetland Flora
Field Office Guide to Plant Species
Cirsium horridulum Michx.
- Family: Aster (Asteraceae)
- Flowering: March-October
- Field Marks: The flowering heads are subtended by a number of spiny-toothed bracts.
- Habitat: Low rich ground, wet ditches, savannas, meadows, flatwoods, marshes, wet prairies, moist or dry disturbed sites.
- Habit: Biennial herb with a thickened root.
- Stems: Upright, branched or unbranched, covered with cobwebby hairs, up to 4 feet tall.
- Leaves: Some forming a basal rosette, others alternate on the stem, simple but deeply divided, sometimes almost to the midvein, with sharp, spine-tipped teeth, smooth or usually hairy, up to 1 foot long, up to 4 inches wide.
- Flowers: Many crowded together into a head, with 1-10 heads per plant; each head up to 2 1/2 inches long, subtended by bracts, some whcih are spiny toothed; flowers all tubular.
- Sepals: 0.
- Petals: 5, yellow to reddish purple, united to form a short tube.
- Stamens: 5.
- Pistils: Ovary inferior.
- Fruits: Achenes smooth, topped by a cluster of plumose bristles up to nearly 2 inches long.
- Notes: The common name, yellow thistle, applies to some plants that live on the coastal plain
that have yellow flowers. Other specimens of the same species on the coastal plain and elsewhere
have reddish purple flowers.
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