Cirsium inamoenum
Cirsium foliosum
Davis' thistle, Greene's thistle, intermountain thistle, Jackson hole thistle
elk thistle, Evert's thistle, foliose thistle, leafy or foliose or elk thistle, leafy thistle
1–several, erect, thinly to densely gray-tomentose with fine, non-septate trichomes;
branches 0–many, ascending.
usually 1, erect, stout, ± fleshy, simple, very leafy, densely villous or tomentose with septate trichomes.
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.
blades linear-oblong to oblanceolate (elliptic), 5–20(–25) × 1–4(–7) cm, subentire to dentate or pinnatifid, lobes lance-oblong to triangular, spinulose to spiny-dentate or shallowly lobed, main spines slender, 2–5(–10) mm, abaxial faces often thinly gray- or white-tomentose with felted arachnoid trichomes, ± villous along major veins with septate trichomes, adaxial green, glabrous to thinly arachnoid, often ± villous with septate trichomes;
basal usually present at flowering, spiny winged-petiolate or sessile;
principal cauline well distributed, proximally winged-petiolate, distally sessile, not or only slightly reduced;
distal often narrower than proximal.
0–25 cm.
0–1 cm.
ovoid or hemispheric to campanulate, 2–3 × 1.5–5 cm, glabrous or loosely floccose to densely arachnoid.
broadly ovoid, 2–2.5 × 1.5–2 cm, green, glabrous to densely villous with septate trichomes on margins.
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.
white to pale pink, 21–25 mm, tubes 12–14 mm, throats (very slender, scarcely larger than tubes) 6–7 mm, lobes 3–4 mm;
style tips 2.5–3 mm, short exserted.
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.
in 4–6 series, imbricate, lanceolate or ovate (outer) to linear-lanceolate (inner), bases appressed, margins of outer entire, abaxial faces without glutinous ridge, apices appressed to ascending, spines straight, slender, 2–3 mm;
apices of inner erect, straight.
1–many, in open corymbiform arrays or crowded near stem tips.
few–many, erect, sessile or subsessile, crowded in dense, woolly, leafy-bracted, subcapitate arrays, closely subtended and overtopped by crowded leafy bracts.
brown, 5–8 mm, apical collars not differentiated;
pappi 12–25 mm.
light brown, 4–5.5 mm, apical collars yellow, narrow;
pappi 23–29 mm, exceeding corollas.
= 32, 34, 36.
= 34.
Cirsium inamoenum
Cirsium foliosum
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.)
Cirsium foliosum occurs in the northern Rockies from Wyoming to the Yukon and eastward to the Slave River area in the Northwest Territories and northeastern Alberta. Reports for Alaska are unconfirmed (R. Lipkin, Alaska Natural Heritage Program, pers. comm.). The name Cirsium foliosum has been misapplied to a wide range of plants across the western United States that now are treated as one or another variety of the polymorphic C. scariosum. The only documented occurrences of C. foliosum in the lower 48 states are in the mountains of northern Wyoming. Somewhat similar plants from other mountain areas of the western United States are treated as C. scariosum var. scariosum. During Pleistocene glaciations the ancestors of C. foliosum undoubtedly occupied a more southerly distribution and very likely came into direct contact with ancestral populations of C. scariosum. The observed similarities between C. foliosum and C. scariosum var. scariosum may be a relic of hybridization in that ancient contact zone. On the other hand, the corolla features of C. foliosum suggest that this is a self-pollinating species, perhaps derived from an ancestral population similar to the modern C. scariosum var. scariosum.
(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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