Cirsium palustre
Cirsium eatonii
cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle
Eaton's thistle, mountaintop thistle, Peck's thistle, Steens Mountain thistle
single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes;
branches 0–few, ascending, (short).
1–several, (fleshy), erect or ascending, simple to sparingly branched in distal 1/2, sometimes openly branched, glabrous to villous or tomentose with septate trichomes, sometimes ± glabrate;
branches on distal stems 0–many, ascending.
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.
blades oblong, 10–30 × 1–5 cm, margins usually strongly undulate, unlobed and spiny-dentate or shallowly to deeply pinnatifid with 10–20 pairs of lobes, teeth or lobes closely spaced, often overlapping, lance-oblong to broadly triangular, deeply 3-lobed, ± spiny-dentate, main spines 2–12 mm, abaxial faces glabrous or villous with septate trichomes along midveins to densely arachnoid-tomentose, adaxial glabrous or villous with septate trichomes along midveins;
basal often present at flowering, spiny winged-petiolate or sessile;
principal cauline many, well distributed, proximally ± winged-petiolate, distally sessile, gradually reduced;
distal not much reduced, often closely subtending heads.
0–1 cm.
0–14+ cm.
ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes.
green or suffused with dark purple, broadly ovoid to campanulate, 2–5 × 1.5–5 cm (appearing wider when pressed), loosely to densely villous or tomentose with septate trichomes and/or arachnoid-tomentose with finer, non-septate trichomes.
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.
ochroleucous or yellow to lavender, pink, or purple, 15–35 mm, tubes 3.5–10 mm, throats 5–14 mm, lobes (linear), 4–12.5 mm;
style tips 3–6 mm, conspicuously exserted beyond corolla lobes.
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.
in 4–5 series, subequal, bases short-appressed, abaxial faces without or with very narrow glutinous ridge, apices usually stiffly ascending to spreading, linear-acicular, tapering to spines 7–35 mm;
outer usually pinnately spiny, sometimes entire;
apices of inner straight, plane or spine-tipped.
few–many in dense clusters at branch tips.
1–many, erect or nodding, closely subtended by spiny-fringed bracts, usually sessile or short-pedunculate and crowded in subcapitate, spiciform, or racemiform (less commonly in openly branched) arrays.
tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny;
pappi 9–11 mm.
dark brown, 5.5–7 mm, apical collars stramineous or not differentiated;
pappi 12–25 mm.
= 34.
Cirsium palustre
Cirsium eatonii
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.)
Varieties 7 (7 in the flora).
Cirsium eatonii is a polymorphic species widely distributed in a high elevation archipelago across the central Rocky Mountains and the Intermountain Region. During Pleistocene glacial episodes, the progenitors of this species complex undoubtedly occupied lower elevation sites and likely had more contiguous populations. Post-glacial isolation of these populations in allopatric high elevation sites has allowed them to differentiate to a greater or lesser extent. Prehistoric or recent introgressive hybridization with other thistle species probably has contributed to the diversification of the complex (R. J. Moore and C. Frankton 1965). Several of the races recognized here as varieties have been treated in the past as species (e.g., C. clokeyi, C. peckii). Their current geographic isolation and more or less distinctive features might support such recognition, but application of this approach across the complex would result in a proliferation of microspecies.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Involucres densely tomentose, individual phyllaries ± obscured by pubescence | → 2 |
1. Involucres glabrous or thinly tomentose, individual phyllaries evident | → 5 |
2. Arrays nodding; corollas yellow or pink to pale purple | var. eriocephalum |
2. Arrays erect; corollas white or pink to deep purple | → 3 |
3. Corolla throats 8–11.5 mm; se Oregon, nw Nevada | var. peckii |
3. Corolla throats 3.5–8 mm | → 4 |
4. Plants 50–150 cm, strictly erect; corollas pink or pale to deep purple; s Colorado | var. hesperium |
4. Plants 10–65 cm, ascending to erect; corollas white to pink or lavender; Idaho and Montana to Utah and n Colorado | var. murdockii |
5. Corollas usually 25–35 mm | → 6 |
5. Corollas usually 17–25 mm | → 7 |
6. Longest pappus bristles 16–18 mm | var. clokeyi |
6. Longest pappus bristles 20–25 mm | var. viperinum |
7. Most outer phyllaries with lateral spines; Nevada and Utah | var. eatonii |
7. Most outer phyllaries without lateral spines; nw Nevada and se Oregon | var. peckii |
BC
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