Cirsium muticum
Cirsium pumilum
chardon mutique, dunce-nettle, horsetops, swamp thistle
pasture thistle
single, erect, villous with septate trichomes or glabrate, distally sometimes thinly tomentose;
branches few–many, ascending.
erect, villous with septate trichomes and sometimes thinly arachnoid tomentose;
branches 0–few, distal, ascending.
ovate to broadly elliptic or obovate, 15–55 × 4–20 cm, deeply pinnatifid, to 7/8 to midribs, lobes linear to lanceolate, acute to acuminate, irregularly few toothed or lobed, main spines 2–3 mm, abaxial faces thinly tomentose or glabrate, villous with septate trichomes on the veins, adaxial faces thinly pilose;
basal usually absent at flowering, petioles spiny-winged, bases tapered;
principal cauline petiolate or sessile, gradually reduced distally, bases sometimes ± clasping, not decurrent;
distal cauline bractlike with narrowly linear lobes, often spinier than the proximal.
blades oblong-elliptic, 5–30+ × 2–10 cm, ± undulate, shallowly to deeply pinnatifid, lobes ovate to broadly triangular, usually separated by broad sinuses, spinose-dentate or lobed, main spines 1.5–7 mm, slender to stout, abaxial faces villous with septate trichomes, at least along veins, sometimes thinly arachnoid, adaxial faces villous with septate trichomes and thinly arachnoid tomentose or subglabrous;
basal often present at flowering, bases tapered;
principal cauline sessile, moderately reduced distally, bases often auriculate-clasping;
distal reduced, similar to proximal.
0–15 cm (sometimes overtopped by distal cauline leaves, not subtended by involucre-like ring of bracts).
0–15+ cm (above distal leaves), leafy-bracted.
ovoid to broadly cylindric or campanulate, 1.7–3 × 1–3 cm, arachnoid.
broadly cylindric to ovoid, 3.5–5 cm, 2.5–3 cm diam. (appearing much wider and hemispheric to campanulate in pressed specimens), loosely arachnoid on phyllary margins or glabrate.
lavender or purple (white), 16–32 mm, tubes 7–15 mm, throats 4.5–10 mm (noticeably wider than tubes), lobes 4–8 mm;
style tips 3.5–5 mm.
pink to purple (white), 40–60 mm, tubes 20–35 mm, throats 11–15 mm, lobes 7–10 mm;
style tips 3–7 mm.
in 8–12 series, strongly imbricate, dull green with darker subapical patch, ovate (outer) to linear-lanceolate (inner), abaxial faces with narrow glutinous ridge, outer and middle appressed, bodies minutely spinulose, apices obtuse to acute, spines erect (sometimes appearing as spreading in dry specimens), 0–0.5 mm;
apices of inner phyllaries straight or ± flexuous, flattened.
in 8–10 series, imbricate, ovate or lanceolate (outer) to lance-linear (inner), abaxial faces with ± prominent glutinous ridge, outer and middle appressed, apices ascending to spreading, spines 1.5–6 mm;
apices of middle and inner narrowed and scabrid-denticulate, innermost spineless, tapered and entire or with expanded, erose-denticulate, flexuous tips.
1–many in ± open corymbiform or paniculiform arrays.
1–few, borne singly at tips of main stem and branches, often closely subtended by 1–several bracts.
dark brown, 4.5–5.5 mm, apical collars yellow, 0.3 mm;
pappi 12–20 mm.
stramineous to brown, 3.5–5 mm, apical collars yellow or colored like body;
pappi 35–45 mm.
= 20, 21, 22, 23, 30.
= 30.
Cirsium muticum
Cirsium pumilum
Cirsium muticum is very widely distributed across the eastern half of North America from the prairies of southeastern Saskatchewan across southern Canada to Newfoundland and south in the United States from North Dakota and Maine to southeastern Texas and northern Florida. It is more common in the northern half of this range and extends from the coastal plain to the Appalachian highlands. The widely scattered populations in coastal lowlands in the southern United States may be relicts of the glacial distribution of the species.
Cirsium muticum is known to hybridize with C. discolor (discussed thereunder) and C. flodmanii. Draining and modification of wetlands have affected populations of C. muticum in some areas.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Flowers of Cirsium pumilum are reportedly sweetly scented.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Spines of outer phyllaries stout, 3–6 mm; plants usually with several long branches; leaves usually lobed nearly to the midvein; roots rarely and only slightly tuberous-thickened; cypselae usually 3.5– 4 mm | var. pumilum |
1. Spines of outer phyllaries slender, 1.5–3 mm; plants simple or distally with a few short branches; leaves usually shallowly lobed; roots often tuberous-thickened; cypselae usually 4.5–5 mm | var. hillii |
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