Cirsium muticum Michx.
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Family: Asteraceae or Compositae
Genus: Cirsium
Species Synonyms: Cirsium muticum var. monticola Fern.
Cirsium muticum var. subpinnatifidum (Britt.) Fern.
Cirsium bigelovii DC.
Carduus muticus (Michx.) Pers.
Common Names: swamp thistle
Canada: Saskatchewan – southern Labrador, Newfoundland, Nova Scotia
Saskatchewan: east-central Saskatchewan; Waskesiu Lake, Tobin Lake, Cumberland Delta, Red River Valley, Upper Assiniboine River
Ecoregion: Aspen Parkland, Boreal Transition, Mid-Boreal Lowland, Mid-Boreal Upland
Saskatchewan: wet woods, clearings, sloughs and lakeshores
Associated Species: Dryopteris austriaca, Lactuca biennis, Prenanthes alba, Rudbeckia hirtella, Sanicula marinlandica, Solidago canadensis
Provincial Status According
to Harms (2003):
Nature Conservancy Status: G5 S2
Saskatchewan Species at
Risk Status:
COSEWIC Status: None
Cirsium muticum is vulnerable because it is somewhat regionally restricted in Saskatchewan. Local populations are usually small. No immediate threats are known for this species.
Height: to 180 cm tall
Roots: taproot fleshy
Stems: biennial, ridged, not winged, multicellular hairs towards the base and beneath head
Leaves: basal and cauline; basal rosette, petiole winged, leaves 10 – 25 cm long, 3 – 10 cm wide, lanceolate, deeply pinnatifed with 4 – 8 pairs of lobes, lobes tipped with short, weak spines; cauline leaves alternate, sessile, twice pinnately lobed, yellow conspicuous midvein below, sparsely hairy, margin with yellow spines
Inflorescence: terminal; heads discoid, to 3.5 cm across; phyllaries in 6 – 8 series, apex blunt or sharp-toothed, tip black to dark brown, midvein dark, tomentose; outer phyllaries 4 – 9 mm long, 2 – 4 mm wide, lacking spine tip, glandular; inner phyllaries to 15 mm, lanceolate
Flowers: florets purple, 20 – 27 mm long, perfect
Fruits: achene 4 – 6 mm long, 1.5 – 2 mm wide, dark brown with yellow apical rim; pappus 13 – 20 mm, whitish, plumose
1 Upper leaf surface with yellowish appressed prickles (scabrous hispid)
Cirsium vulgare
1 Upper leaf surface without prickles, may be glabrous to tomentose
2 Rhizomes creeping; heads unisexual (plants dioecious); involucre 1 – 2 cm tall
C. arvense
2 Stems arise from center of previous year’s rosette; flowers perfect; involucres taller
3 Outer involucral bracts without spine tip
C. muticum
3 Outer involucral bracts with spine tip
4 Middle and upper cauline leaves strongly decurrent
C. canescens
4 Middle and upper cauline leaves sessile or clasping, if decurrent then for < 1 cm
5 Leaves not densely white tomentose beneath; inflorescence more compact; phyllaries lacking glutinous dorsal ridge
C. drummondii
5 Leaves densely white tomentose beneath; inflorescence loose; phyllaries with a dark, thickened glutinous dorsal ridge
6 Stems green and lightly pilose or floccose, may have multicellular hairs; upper leaf surface green and glabrous (or minutely hirsute)
C. discolor
6 Stems densely white tomentose at least on middle and above; upper leaf surface persistently more or less gray tomentose
7 Cauline leaves ovate to lanceolate, shallowly lobed to subentire; propagating by shoots from deep tap roots; involucre to 4 cm high
C. undulatum
7 Cauline leaves elliptic to oblanceolate, shallowly lobed to pinnatifed; propagating by buds borne on horizontal roots; involucre < 2.5 cm
C. flodmanii