Cirsium pulcherrimum
Cirsium foliosum
Wyoming thistle
elk thistle, Evert's thistle, foliose thistle, leafy or foliose or elk thistle, leafy thistle
1–few, erect or ascending, arachnoid-tomentose or ± glabrate;
branches 0–5+, usually in distal 1/2, ascending.
usually 1, erect, stout, ± fleshy, simple, very leafy, densely villous or tomentose with septate trichomes.
blades linear to oblong, oblanceolate, or elliptic, 5–25 × 0.6–7 cm, unlobed and merely spinulose or spiny-dentate to regularly pinnatifid, lobes 5–8(–many) pairs, well separated, usually with broad, U-shaped sinuses to crowded, linear to triangular-ovate, ascending-spreading to retrorse, merely spinulose to coarsely dentate or few lobed, main spines 2–7 mm, ± slender, abaxial faces gray to white, usually densely arachnoid-tomentose, sometimes ± glabrate, sometimes villous with septate trichomes along veins, adaxial green, glabrous or less commonly thinly to densely gray-tomentose;
basal often present at flowering, spiny winged-petiolate;
principal cauline well distributed, gradually reduced distally, proximal usually winged-petiolate, mid and distal sessile, bases decurrent as spiny wings 1.5–3.5 cm;
distalmost reduced, ± bractlike.
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.
0–15 cm.
0–1 cm.
ovoid to campanulate, 1.8–2.7 × 1–2 cm, thinly arachnoid-tomentose or glabrate.
broadly ovoid, 2–2.5 × 1.5–2 cm, green, glabrous to densely villous with septate trichomes on margins.
pink to purple (creamy white), 18–25 mm, tubes 7–9 mm, throats 5.5–7.5 mm, lobes 4–8 mm;
style tips 3–5.5 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 6–7 series, ± imbricate, green or with dark subapical patch or appendage, linear to linear-lanceolate, margins entire, abaxial faces with narrow glutinous ridge;
outer and middle bases appressed, apical appendages spreading to stiffly ascending, linear-lanceolate to acicular, entire, spines spreading or ascending, stout, 2–7 mm, often flattened;
apices of inner stiffly erect or sometimes flexuous, narrow, flat.
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–few, borne singly or in 2–3-headed clusters in ± congested flat-topped or racemiform arrays at tips of main stem and branches, sometimes also in distal axils.
few–many, erect, sessile or subsessile, crowded in dense, woolly, leafy-bracted, subcapitate arrays, closely subtended and overtopped by crowded leafy bracts.
tan to dark brown, 5–6 mm, apical collars yellow, narrow;
pappi 14–16 mm.
light brown, 4–5.5 mm, apical collars yellow, narrow;
pappi 23–29 mm, exceeding corollas.
= 34.
= 34.
Cirsium pulcherrimum
Cirsium foliosum
Varieties 2 (2 in the flora).
Cirsium pulcherrimum is closely related to C. clavatum. In southeastern Wyoming and northern Colorado some plants combine foliage and involucral characters of C. pulcherrimum var. pulcherrimum and C. clavatum var. americanum. The inheritance of these characters needs to be examined at the population level to determine whether the intermediates are hybrids or the products of past introgression or incomplete differentiation.
(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. Distal leaf face gray- to white-tomentose; cypselae without stramineous apical collar | var. aridum |
1. Distal leaf face usually green, glabrous or ± glabrate, but sometimes persistently tomentose; cypselae often with narrow stramineous apical collar | var. pulcherrimum |
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
BC
OR
Flora NW
