Cirsium muticum Michx.
Family: Asteraceae
swamp thistle
[Carduus muticus (Michx.) Pers.,  more]
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Christopher Noll  
Etymology: muticum = blunt, without a point.
Plants
: 4 - 7 ft tall, coarse, stem not winged.
Leaves
: Softly spiny, deeply pinnately-divided, with lance-like to oblong segments.
Flowers
: Head purple to pink, 1 1/2 in wide, bract tips white-wooly but not spiny.
Habitat
: Wet calcareous shores, fens, sedge meadows, streamsides, and conifer swamps.
Phenology
: Blooms July to October.
Conservation Status
: Native.
- flower heads < 3 cm broad, attractive deep pink/purple color

- involucral bracts without spines (but can be mucronate), sticky, cobwebby

- leaves deeply pinnatifid, green and slightly cobwebby below

- spines on leaves < 2.5 (3.5) mm, weak

- stems relatively unarmed

- in wet haitats esp. calcareous shores, fens, sedge meadows, conifer swamps, and along streams

Robust to slender biennials 8-18 (-20) dm tall, with a shallow lateral root system and weak ephemeral taproot. Stem hollow, pubescent at base, glabrate above. Leaves thin, ovate to lanceolate, 10-30 cm long, green and sparsely crisped-hispid above, tomentulose beneath, deeply pinnatifid, the lobes lanceolate to oblong-ovate, often with alternate secondary lobes, tipped with short spines and with prickly margins. Heads with deep purple corollas, rather few, mostly solitary or rarely clustered on cobwebby peduncles. Involucre 22-27 mm high, the bracts cobwebby with very prominent glutinous ridges and without mucronate tips (or these only 0.1-0.3 mm long [lOX]), the outer bracts obtuse, the inner lanceolate with erose tips. Achenes 3.3-4.5 mm long, black.

Johnson, M.E. and H.H. Iltis. 1963. Preliminary reports on the flora of Wisconsin: No. 48. Compositae Family. Wisconsin Academy of Sciences, Arts & Letters. 52:255-342.

Throughout Wisconsin in open moist habitats, most prevalent, especially in the south, in open wet prairies and rather rare in wetmesic and mesic prairies (Curtis 1955), common in poorly drained soil at the edge of bogs, in wet sedge meadows, there with Carex spp., Solidago uliginosa, S. patula, S. gigantea and Spiraea tomentosa, around springs, and in tamarack swamps, in N. Wisconsin often in most spruce-fir-White Cedar or aspen-Paper Birch woods, usually in highly organic, mucky soil, rarely as a roadside weed in burned, second-growth, sandy woods. Flowering from mid-July to mid-September; fruiting from mid-August to early October.

This species hybridizes with Cirsium discolor.

Johnson, M.E. and H.H. Iltis. 1963. Preliminary reports on the flora of Wisconsin: No. 48. Compositae Family. Wisconsin Academy of Sciences, Arts & Letters. 52:255-342.

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Christopher Noll  
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Christopher Noll  
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Merel R. Black  
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Merel R. Black  
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Emmet J. Judziewicz  
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Scott A. Milburn  
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Merel R. Black  
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Emmet J. Judziewicz  
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