Cirsium flodmanii
Cirsium palustre
chardon de Flodman, Flodman's thistle, prairie thistle
cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle
1–several, erect, gray- or white-tomentose;
branches 0–few, ascending.
single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes;
branches 0–few, ascending, (short).
blades oblong-oblanceolate to narrowly elliptic, 4–40 × 1–10 cm, bases usually not decurrent, finely spiny-toothed and undivided to coarsely toothed or deeply pinnatifid, lobes broadly triangular to linear-lanceolate, often revolute-margined, main spines 1–7 mm, abaxial faces white-tomentose, adaxial faces green, thinly tomentose, ± glabrate;
basal usually absent or withered at flowering, winged petiolate;
principal cauline proximally winged-petiolate, distally sessile, well distributed, gradually reduced, bases usually not decurrent;
distal cauline well developed.
blades narrowly elliptic to oblanceolate, 15–30+ × 3–10 cm, margins shallowly to very deeply pinnatifid, narrow lobes separated by broad sinuses, spiny-dentate to lobed, main spines 2–6 mm, abaxial villous to tomentose with jointed trichomes, sometimes also thinly tomentose with fine unbranched trichomes, adaxial faces villous with septate trichomes or glabrate;
basal often present at flowering, petioles spiny-winged, bases tapered;
cauline many, sessile, gradually reduced and becoming widely spaced above, bases long-decurrent with prominently spiny wings;
distal cauline deeply pinnatifid with few-toothed spine-tipped lobes.
0–5 cm (elevated above distal leaves).
0–1 cm.
ovoid to broadly campanulate, 2–3.5 × 2.5–3.5 cm, thinly arachnoid.
ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes.
purple (white), 23–36 mm, tubes 12–15 mm, throats 6–8.5 mm, lobes 5–9 mm;
style tips 4–7 mm.
lavender to purple (white), 11–13 mm, tubes 5–7 mm, throats 2–3 mm, lobes 3–4.5 mm;
style tips 1.5–2 mm.
in 7–12 series, strongly imbricate, greenish with subapical darker central zone, ovate or lanceolate (outer) to linear (inner), abaxial faces with prominent glutinous ridge;
outer and middle entire, bodies appressed, entire, acute, spines abruptly spreading, slender, 2–4 mm;
apices of inner spreading, flexuous, narrow, flattened, finely serrulate, ± scabrous.
in 5–7 series, strongly imbricate, greenish, or with purplish tinge, lanceolate to ovate (outer) or linear-lanceolate (inner), margins thinly arachnoid-ciliate, abaxial faces with narrow glutinous ridge, outer and middle appressed, entire, apices acute, mucronate or spines erect or spreading, weak, 0.3–1 mm;
apices of inner phyllaries purplish, linear-attenuate, scarious, flat.
erect, borne singly and terminal on main stem and branches, or few in corymbiform arrays from distal axils (not subtended by ring of spiny-margined bracts).
few–many in dense clusters at branch tips.
light brown, 3–5 mm, apical collars stramineous, 0.5–1 mm;
pappi (white or tawny) 20–30 mm.
tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny;
pappi 9–11 mm.
= 22, 24.
= 34.
Cirsium flodmanii
Cirsium palustre
Cirsium flodmanii ranges from Saskatchewan and Alberta south through the northern Great Plains and intermountain valleys of Montana and Wyoming to northeastern Colorado and east through the prairies to Minnesota and Iowa, and in widely scattered locations eastward to northern Illinois, southern Wisconsin, southern Ontario, and southern Quebec. It is known to hybridize with C. muticum and C. undulatum. Hybrids between C. flodmanii and C. undulatum are highly sterile with numerous meiotic irregularities (S. Dabydeen 1987).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cirsium palustre is a noxious weed, native to Europe, that invasively spreads through wetland communities, forming impenetrable spiny stands as it displaces native species. The range of this pernicious weed in North America is rapidly expanding. It has the potential to spread into boreal forest areas across the continent; in Europe it grows nearly to the Arctic Circle. The rapid spread of C. palustre in Michigan (E. G. Voss 1972–1996, vol. 3) is indicative of its invasiveness. Spontaneous hybrids between C. palustre and C. arvense have been reported from England and other European countries (W. A. Sledge 1975) and can be expected wherever these species grow together in North America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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