Cirsium inamoenum
Cirsium helenioides
Davis' thistle, Greene's thistle, intermountain thistle, Jackson hole thistle
melancholy thistle
1–several, erect, thinly to densely gray-tomentose with fine, non-septate trichomes;
branches 0–many, ascending.
single, erect, ± arachnoid-tomentose;
branches 0 or few, ascending.
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.
oblong to broadly lanceolate, 20–40 × 4–8 cm, finely spinulose-dentate or proximal cauline pinnatifid, lobes undivided, finely spinulose-dentate, main spines 1–2 mm, abaxial faces white-tomentose (with non-septate trichomes), adaxial glabrous;
basal present at flowering, petiolate, bases tapered;
cauline sessile, reduced distally, bases clasping, not decurrent;
distal (few, well separated), oblong or linear, the uppermost reduced to linear bracts.
0–25 cm.
2–10(–30) cm (elevated above distal leaves).
ovoid or hemispheric to campanulate, 2–3 × 1.5–5 cm, glabrous or loosely floccose to densely arachnoid.
broadly ovoid, 2–3 × 2–3.5 cm, glabrous or loosely arachnoid.
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.
red-purple, 25–30 mm, tubes 10–23 mm, throats 8–14 mm (noticeably wider than tubes), lobes 7–10 mm;
style tips 4–5 mm.
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 8–10 series, imbricate, green, ovate or lanceolate (outer) to linear-lanceolate (inner), abaxial faces with a prominent elongate glutinous ridge, outer and middle tightly appressed, margins entire, apices with ascending, weak spines 0–1 mm;
apices of inner phyllaries attenuate, flat.
1–many, in open corymbiform arrays or crowded near stem tips.
borne singly or less commonly 2–5 in terminal clusters.
brown, 5–8 mm, apical collars not differentiated;
pappi 12–25 mm.
light brown, 3–5 mm, bodies and apical collars concolorous;
pappi 20–30 mm.
= 32, 34, 36.
= 34.
Cirsium inamoenum
Cirsium helenioides
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 helenioides is one of only two species of the genus that have native populations in the Old World and the flora area. Neither reaches the North American mainland.
The conservation status of Cirsium helenioides is not known; it is known in the flora area only from a single fjord and possibly should be considered of conservation concern.
of conservation concern
(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 |
- Local floras:
OR, 
WA - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
USDA Plants Database
