Flora of North America species comparison

The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Cirsium scariosum

Cirsium inamoenum

chardon écailleux, dinnerplate thistle, elk thistle, meadow thistle

Davis' thistle, Greene's thistle, intermountain thistle, Jackson hole thistle
Habit Biennials or monocarpic perennials, acaulescent, short caulescent and forming low rounded mounds, or caulescent and erect, 0–200 cm; taprooted. Biennials or monocarpic perennials, 20–100 cm; deeply taprooted.
Stems

absent, or with crowded branches from near base, or simple and erect, often fleshy and thickened, glabrous to thinly gray- tomentose, often villous with septate trichomes.

1–several, erect, thinly to densely gray-tomentose with fine, non-septate trichomes;

branches 0–many, ascending.
Leaves

blades linear to elliptic, 5–20 × 3–7 cm, plane to strongly undulate, unlobed or shallowly to deeply pinnatifid, lobes linear-lanceolate to broadly triangular, closely spaced, spreading, spinose-dentate or lobed, main spines slender to stout, 2–15+ mm, abaxial faces glabrous or thinly to densely tomentose, ± villous with septate trichomes along the veins, glabrate or trichomes persistent, adaxial thinly arachnoid tomentose and soon glabrescent;

basal often present at flowering, sessile or winged-petiolate;

cauline many in caulescent forms, reduced distally or not, winged-petiolate or distal sessile;

distal often well developed, similar to proximal, sometimes much narrower and bractlike.

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.
Peduncles

0–10 cm, leafy-bracted.

0–25 cm.
Involucres

ovoid to hemispheric, 2–4 × 1.5–6 cm, loosely arachnoid on phyllary margins or glabrate.

ovoid or hemispheric to campanulate, 2–3 × 1.5–5 cm, glabrous or loosely floccose to densely arachnoid.
Corollas

white or pale lavender to purple, 20–40 mm, tubes 7–24 mm, throats 4–12 mm (noticeably larger than tubes), lobes 4–10 mm;

style tips 3.5–8 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.
Phyllaries

in 5–10 series, imbricate, ovate or lanceolate (outer) to linear or linear-lanceolate (inner), margins (outer) entire or scarious-fringed, abaxial faces without glutinous ridge;

outer and mid appressed, spines erect to spreading 0.5–13 mm;

apices of mid and inner narrowed and scabro-denticulate or with expanded, erose-dentate tips, spineless or tipped with flattened spines.

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.
Heads

1–many, erect, borne singly or often densely crowded in spiciform, racemiform, or subcapitate arrays, especially in acaulescent or short-caulescent plants, often closely subtended by distalmost leaves.

1–many, in open corymbiform arrays or crowded near stem tips.
Cypselae

light to dark brown, 4–6.5 mm, apical collars usually colored like body;

pappi 17–35 mm, white to tan.

brown, 5–8 mm, apical collars not differentiated;

pappi 12–25 mm.
2n

= 34, 36.

= 32, 34, 36.

Cirsium scariosum

Cirsium inamoenum
Distribution
from FNA
AZ; CA; CO; ID; MT; NM; NV; OR; UT; WA; WY; AB; BC; QC; disjunct to e Que (Mingan Archipelago)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; NV; OR; UT; WA; WY
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 8 (8 in the flora).

Cirsium scariosum is a widely distributed complex of intergrading races distributed from southwestern Canada to northwestern Mexico. These plants range from acaulescent rosettes with a tight cluster of sessile heads to tall, erect, unbranched plants, or moundlike, more or less openly branched herbs. Acaulescent and caulescent plants sometimes occur in the same population.

Members of this complex have been variously treated in the past. F. Petrak (1917) recognized ten species plus several subspecies for the taxa I am treating here as C. scariosum (in the broad sense). In floras, the names C. drummondii and C. foliosum have been widely misapplied to these plants (R. J. Moore and C. Frankton 1964). The latter two species, while clearly related to C. scariosum, have a range restricted mostly to Canada. Moore and Frankton (1967) attempted to bring order to the complex and recognized four species for plants that I include here in C. scariosum: C. acaulescens, C. congdonii, C. coloradense, and C. scariosum in the restricted sense. Moore and Frankton substituted the prior name C. tioganum for C. acaulescens. Unfortunately they did not extend their study widely enough and did not include some members of the complex in their investigations. S. L. Welsh (1982) proposed C. scariosum var. thorneae from Utah and lumped the various species recognized by Moore and Frankton within a highly polymorphic var. scariosum. After consulting with A. Cronquist and studying his manuscript treatment of Cirsium for the Intermountain Flora, D. J. Keil and C. E. Turner (1993) also accepted a broadly construed C. scariosum. Cronquist (1994) treated C. scariosum as an extremely variable species that included the four species recognized by Moore and Frankton plus the variety proposed by Welsh. Cronquist chose to not recognize infraspecific taxa.

In the present treatment I have examined these plants from a biogeographic perspective with the goal of discerning regional patterns of variation. The large number of specimens available has allowed me to examine distributional patterns in relation to the topography and biogeographic history of the regions where this species occurs. My field studies also have provided me with observations that help to explain some of the anomalous specimens represented in herbaria. Although the variation within and between populations is sometimes amazing, more-or-less differentiated geographic races can be discerned. Because of the extraordinary and overlapping patterns of variation across the range of Cirsium scariosum, the following key to varieties should be regarded as at best an approximation.

(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.)
Key
1. Plants acaulescent (occasional short-caulescent individuals sometimes present in a population)
→ 2
1. Plants caulescent (occasional acaulescent individuals sometimes present in a population)
→ 4
2. Corollas pink to purple; Sierra Nevada of w Nevada and e California to San Bernardino Mountains of s California
var. congdonii
2. Corollas white to faintly pink-or lilac-tinged; widespread
→ 3
3. Abaxial leaf faces usually gray-tomentose; widespread, Colorado to s Oregon, n California
var. americanum
3. Abaxial leaf faces usually green, glabrous or glabrate; s. California
var. citrinum
4. Larger leaf spines 1–3 cm
Cirsium scariosum var. thorneae
4. Larger leaf spines usually shorter
→ 5
5. Corollas purple
→ 6
5. Corollas white to faintly pink- or lilac-tinged
→ 7
6. Corolla lobes 5.5–8 mm; sw. Idaho, n Nevada, se Oregon
var. toiyabense
6. Corolla lobes 3.5–6 mm; e Oregon to sw Montana
var. scariosum
7. Stems usually proximally branched, plants often forming low, rounded mound; heads usually borne on short to ± elongate lateral branches; corollas 26–36 mm
→ 8
7. Stems usually erect, proximally unbranched; heads usually sessile or short-pedunculate in subcapitate to spiciform or racemiform arrays, usually closely subtended by numerous distal leaves; corollas 20–29 mm
→ 9
8. Apices of inner phyllaries acuminate and entire or rarely toothed; s California
var. citrinum
8. Apices of inner phyllaries usually expanded as a scarious, erose-toothed appendage; ne California, se Oregon
var. robustum
9. Heads usually ± tightly clustered at stem tips, closely subtended and often overtopped by crowded distal leaves; distal leaves ± thin, usually fringed with numerous weak spines, often ± unpigmented proximally or tinged pink to purplish
var. scariosum
9. Heads usually in ± leafy, racemiform arrays, usually subtended by ± reduced, bractlike distal leaves; distal leaves firm, strongly spiny, usually green throughout
var. coloradense
1. Corollas white or pale lavender
var. inamoenum
1. Corollas lavender to rich pink-purple
var. davisii
Source FNA vol. 19, p. 1. FNA vol. 19, p. 134.
Parent taxa Asteraceae > tribe Cardueae > Cirsium Asteraceae > tribe Cardueae > Cirsium
Sibling taxa
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevifolium, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, C. horridulum, C. hydrophilum, C. inamoenum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ochrocentrum, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevifolium, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, C. horridulum, C. hydrophilum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ochrocentrum, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. scariosum, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
Subordinate taxa
C. scariosum var. americanum, C. scariosum var. citrinum, C. scariosum var. coloradense, C. scariosum var. congdonii, C. scariosum var. robustum, C. scariosum var. scariosum, C. scariosum var. toiyabense
C. inamoenum var. davisii, C. inamoenum var. inamoenum
Synonyms C. hookerianum var. scariosum Carduus inamoenus
Name authority Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 420. (1841) (Greene) D. J. Keil: Sida 21: 214. (2004)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



Type/paste one or more Latin names into the boxes above; matching taxa will show up below the box as you type. You can use the up/down arrow keys to move through the list.

(If the plant you're looking for doesn't show up in the auto-complete list, that means it either isn't described in Flora of North America yet, or it's listed under a synonym. And please note that Flora of North America is still missing several plant families, including Fabaceae, Apiaceae, Boraginaceae, and Polemoniaceae.)

Choose a data source: Flora of North America, OregonFlora, UW Burke Herbarium

The species comparison tool is brought to you by:
Northwest Wildflowers