Cirsium scariosum |
Cirsium ochrocentrum |
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chardon écailleux, dinnerplate thistle, elk thistle, meadow thistle |
Beaumont thistle, yellowspine thistle |
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Habit | Biennials or monocarpic perennials, acaulescent, short caulescent and forming low rounded mounds, or caulescent and erect, 0–200 cm; taprooted. | Perennials, 30–90 cm; crown sprouts or runner roots producing adventitious buds. | ||||||||||||||||||||||||||||||||||||||||
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. |
1–20+, erect or ascending, densely gray-tomentose with non-septate trichomes; branches 0 or few, usually in distal 1/2, ascending. |
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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 oblong to narrowly elliptic, 10–30 × 2–8 cm, strongly undulate, margins coarsely dentate or shallowly to deeply pinnatifid with 8–15 pairs of lobes 0.5–2 cm, often revolute, lobes ± triangular, closely spaced, spreading, spinose-dentate and cleft into 2–5 spine-tipped divisions, main spines 5–20 mm, yellowish, abaxial faces densely white-tomentose, adaxial thinly gray-tomentose; basal usually present at flowering, winged-petiolate; principal cauline sessile, progressively reduced distally, bases ± auriculate to long-decurrent as spiny wings; distal cauline usually much reduced, less lobed. |
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Peduncles | 0–10 cm, leafy-bracted. |
0–4 cm. |
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Involucres | ovoid to hemispheric, 2–4 × 1.5–6 cm, loosely arachnoid on phyllary margins or glabrate. |
ovoid to hemispheric or broadly campanulate, 2.5–4.5 × 2.5–4.5 cm in first-formed heads, often smaller in later ones, loosely arachnoid on phyllary margins or glabrate. |
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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. |
white or pale lavender to purple, pink, or red, 25–45 mm, tubes 8–25 mm, throats 6–17 mm, lobes 6–15 mm; style tips 2–8 mm. |
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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 5–10 series, imbricate, ovate (outer) to linear-lanceolate (inner), margins entire, abaxial faces with narrow glutinous ridge; outer and middle appressed, spines spreading, 3–12 mm; apices of inner often flexuous, expanded and flat, scabrid-margined, sometimes erose, spineless. |
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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–few, in leafy, ± corymbiform arrays. |
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Cypselae | light to dark brown, 4–6.5 mm, apical collars usually colored like body; pappi 17–35 mm, white to tan. |
light brown, sometimes with lighter or darker streaks, 6–9 mm, apical collars colored like the body, narrow; pappi (white or tawny), 20–40 mm, usually noticeably shorter than corolla. |
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2n | = 34, 36. |
= 30, 31, 32, 34. |
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Cirsium scariosum |
Cirsium ochrocentrum |
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Distribution |
AZ; CA; CO; ID; MT; NM; NV; OR; UT; WA; WY; AB; BC; QC; disjunct to e Que (Mingan Archipelago)
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AZ; CA; CO; KS; NE; NM; OK; SD; TX; UT; WY; n Mexico
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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). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 1. | FNA vol. 19, p. 123. | ||||||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium | ||||||||||||||||||||||||||||||||||||||||
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Synonyms | C. hookerianum var. scariosum | |||||||||||||||||||||||||||||||||||||||||
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 420. (1841) | A. Gray: Mem. Amer. Acad. Arts, n. s. 4: 110. (1849) | ||||||||||||||||||||||||||||||||||||||||
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