Northern Prairie Wildlife Research Center
Western Wetland Flora
Field Office Guide to Plant Species
Cirsium arvense (L.) Scop.
- Family: Composite (Compositae)
- Flowering: June-August
- Field Marks: This thistle can be distinguished usually by its small flower heads that are usually less than 1 inch long and 1/2 inch wide.
- Habitat: Bottomland areas, ditches, old fields, disturbed areas.
- Habit: Perennial herb from a thickened, deep rootstock.
- Stems: Upright, branched, up to 4 feet tall, usually covered with white, cobwebby hairs.
- Leaves: Alternate, simple, usually pinnately lobed, up to 6 inches long, up to 3 inches wide, smooth or white-hairy, the lobes bearing sharp spines; leaf stalk up to 1/2 inch long or absent.
- Flowers: Many crowded together into a head, with several heads per plant; each head less than 1 inch long, less than 1/2 inch across, subtended by 5-6 rows of small spine-tipped,
green bracts; flowers all tubular.
- Sepals: 0.
- Petals: 5, pink or purple, forming a tube up to 1 inch long.
- Stamens: 5.
- Pistils: Ovary inferior.
- Fruits: Achenes pale brown, topped by a cluster of white or gray plumose bristles up to 1 inch long.
- Notes: The female and male flowers are usually borne in separate heads on separate plants.
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