Cirsium palustre
Cirsium inamoenum
cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle
Davis' thistle, Greene's thistle, intermountain thistle, Jackson hole thistle
single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes;
branches 0–few, ascending, (short).
1–several, erect, thinly to densely gray-tomentose with fine, non-septate trichomes;
branches 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 oblanceolate or elliptic, 10–35 × 1–7 cm, unlobed and spinulose to dentate or deeply pinnatifid, usually 5–8 pairs of lobes, well separated, linear to lance-triangular, spinulose to few toothed or lobed, main spines 2–7 mm, abaxial faces densely gray-tomentose or sometimes ± glabrate, adaxial gray to ± green, thinly tomentose or ± glabrate;
basal sometimes present at flowering, narrowly winged-petiolate;
principal cauline well distributed, gradually reduced, sometimes spinier than basal;
proximal winged-petiolate, mid sessile, bases spiny-winged, decurrent 1–3 cm;
distal becoming bractlike, often unlobed or less deeply divided than proximal.
0–1 cm.
0–25 cm.
ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes.
ovoid or hemispheric to campanulate, 2–3 × 1.5–5 cm, glabrous or loosely floccose to densely arachnoid.
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.
dull white or faintly lavender-tinged to bright pink-purple, 19–31 mm, tubes 7–13 mm, throats 6.5–9.5 mm, lobes 4–8 mm;
style tips 3.5–7 mm.
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 6–10 series, strongly imbricate or sometimes subequal, greenish to brown, ovate to linear-lanceolate (outer) to linear (inner), entire, abaxial faces with narrow or scarcely developed glutinous ridge;
outer and mid appressed or apices ascending to spreading, linear, bodies entire, spines ascending to abruptly spreading, usually fine, 2–6 mm;
apices of inner narrow, spine-tipped or spineless.
few–many in dense clusters at branch tips.
1–many, in open corymbiform arrays or crowded near stem tips.
tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny;
pappi 9–11 mm.
brown, 5–8 mm, apical collars not differentiated;
pappi 12–25 mm.
= 34.
= 32, 34, 36.
Cirsium palustre
Cirsium inamoenum
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 2 (2 in the flora).
Cirsium inamoenum is a variable complex across the northern Great Basin and adjacent mountains. A. Cronquist (1994) treated this complex as a single species under the name C. subniveum without infraspecific taxa and including taxa that formerly had been assigned to C. utahense (e.g., J. T. Howell 1960b). Some populations consist of small-headed, white-flowered plants with strong involucres and short, appressed phyllaries. Others have larger heads, white or lavender to pink-purple corollas, and phyllaries with longer, ascending to spreading tips. My treatment of this complex as C. inamoenum is similarly inclusive as was Cronquist’s treatment of C. subniveum, except that I believe C. humboldtense, which Cronquist included, is probably a derivative of hybridization between C. subniveum and C. eatonii var. peckii. I have observed such hybrids on the slopes of Steens Mountain in Harney County, Oregon, and the type of C. humboldtense closely resembles some of the introgressants. I have examined several other specimens that are likely the products of hybridization of C. inamoenum with other varieties of C. eatonii.
I have chosen to recognize racial differentiation within Cirsium inamoenum at the rank of variety. The main difference between Cirsium inamoenum var. inamoenum and var. davisii is corolla color. Unfortunately this feature is sometimes difficult to determine on herbarium specimens, and many collectors fail to include corolla color on specimen labels. Some geographic overlap occurs between var. davisii, which has a distribution centered in northeastern Utah, southeastern Idaho, and adjacent southwestern Wyoming, and the more widespread var. inamoenum.
Plants of northeastern Oregon, southeastern Washington, and adjacent western Idaho often have large heads and densely tomentose foliage. These were named Cirsium wallowense by Peck. Similar plants occur sporadically in other portions of the range of Cirsium inamoenum var. inamoenum and I chose not to recognize these northwestern populations as a third variety. Additional study might clarify the relationships of these plants.
Some specimens of Cirsium inamoenum in central Nevada and Utah approach C. neomexicanum. It seems likely that these species have interacted in the past.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Corollas white or pale lavender | var. inamoenum |
1. Corollas lavender to rich pink-purple | var. davisii |
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