Species: Cirsium muticum Michx.

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Cirsium muticum Michx.

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TAXONOMY

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

DISTRIBUTION

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

HABITAT

Saskatchewan:

wet woods, clearings, sloughs and lakeshores

Associated Species:

Dryopteris austriaca, Lactuca biennis, Prenanthes alba, Rudbeckia hirtella, Sanicula marinlandica, Solidago canadensis

RARITY STATUS

Provincial Status According
to Harms (2003):

Vulnerable

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

None

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.

SPECIES DESCRIPTION

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

CIRSIUM KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Upper leaf surface with yellowish appressed prickles (scabrous hispid)	Cirsium vulgare
1 Upper leaf surface without prickles, may be glabrous to tomentose	2

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

3 Outer involucral bracts without spine tip	C. muticum
3 Outer involucral bracts with spine tip	4

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

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

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

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