Cirsium scariosum
Cirsium muticum
chardon écailleux, dinnerplate thistle, elk thistle, meadow thistle
chardon mutique, dunce-nettle, horsetops, swamp thistle
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.
single, erect, villous with septate trichomes or glabrate, distally sometimes thinly tomentose;
branches few–many, ascending.
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.
ovate to broadly elliptic or obovate, 15–55 × 4–20 cm, deeply pinnatifid, to 7/8 to midribs, lobes linear to lanceolate, acute to acuminate, irregularly few toothed or lobed, main spines 2–3 mm, abaxial faces thinly tomentose or glabrate, villous with septate trichomes on the veins, adaxial faces thinly pilose;
basal usually absent at flowering, petioles spiny-winged, bases tapered;
principal cauline petiolate or sessile, gradually reduced distally, bases sometimes ± clasping, not decurrent;
distal cauline bractlike with narrowly linear lobes, often spinier than the proximal.
0–10 cm, leafy-bracted.
0–15 cm (sometimes overtopped by distal cauline leaves, not subtended by involucre-like ring of bracts).
ovoid to hemispheric, 2–4 × 1.5–6 cm, loosely arachnoid on phyllary margins or glabrate.
ovoid to broadly cylindric or campanulate, 1.7–3 × 1–3 cm, arachnoid.
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.
lavender or purple (white), 16–32 mm, tubes 7–15 mm, throats 4.5–10 mm (noticeably wider than tubes), lobes 4–8 mm;
style tips 3.5–5 mm.
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 8–12 series, strongly imbricate, dull green with darker subapical patch, ovate (outer) to linear-lanceolate (inner), abaxial faces with narrow glutinous ridge, outer and middle appressed, bodies minutely spinulose, apices obtuse to acute, spines erect (sometimes appearing as spreading in dry specimens), 0–0.5 mm;
apices of inner phyllaries straight or ± flexuous, flattened.
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 or paniculiform arrays.
light to dark brown, 4–6.5 mm, apical collars usually colored like body;
pappi 17–35 mm, white to tan.
dark brown, 4.5–5.5 mm, apical collars yellow, 0.3 mm;
pappi 12–20 mm.
= 34, 36.
= 20, 21, 22, 23, 30.
Cirsium scariosum
Cirsium muticum
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.)
Cirsium muticum is very widely distributed across the eastern half of North America from the prairies of southeastern Saskatchewan across southern Canada to Newfoundland and south in the United States from North Dakota and Maine to southeastern Texas and northern Florida. It is more common in the northern half of this range and extends from the coastal plain to the Appalachian highlands. The widely scattered populations in coastal lowlands in the southern United States may be relicts of the glacial distribution of the species.
Cirsium muticum is known to hybridize with C. discolor (discussed thereunder) and C. flodmanii. Draining and modification of wetlands have affected populations of C. muticum in some areas.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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 |
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria, Turner Photog. 
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