Cirsium ochrocentrum |
Cirsium longistylum |
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Beaumont thistle, yellowspine thistle |
long-style thistle |
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Habit | Perennials, 30–90 cm; crown sprouts or runner roots producing adventitious buds. | Perennials monocarpic, 40–150 cm; taprooted. | ||||
Stems | 1–20+, erect or ascending, densely gray-tomentose with non-septate trichomes; branches 0 or few, usually in distal 1/2, ascending. |
usually 1, erect, less commonly several, ascending, simple to sparingly short-branched in distal 1/2, less commonly openly branched, villous with jointed trichomes; branches on distal stems 0–many, short, ascending. |
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Leaves | 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. |
blades linear to oblong or elliptic, 10–30+ × 1–10 cm, margins flat to undulate, subentire to coarsely dentate or shallowly to deeply pinnatifid, lobes lance-oblong to broadly triangular, spinulose to spiny-dentate or shallowly lobed, main spines 3–12 mm, abaxial faces green and subglabrous to gray- or white-tomentose with felted arachnoid trichomes, ± villous to tomentose along major veins with septate trichomes, rarely glabrous or glabrate, adaxial ± green, glabrous or villous with septate trichomes; basal often present at flowering, spiny winged-petiolate or sessile; principal cauline well distributed, proximally winged-petiolate, distally sessile, gradually reduced, bases sometimes short-decurrent (0–2 cm); distal ± reduced, often narrower than the proximal, sometimes with non-pigmented bases. |
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Peduncles | 0–4 cm. |
0–15+ cm. |
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Involucres | 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. |
(green), broadly ovoid, 1.5–2.5 × 1.5–2.5 cm, loosely villous with septate trichomes, sparingly if at all arachnoid. |
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Corollas | 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. |
white, ochroleucous, 19–23 mm, tubes 6.5–8.5 mm, throats 7.5–11 mm, lobes 4–5 mm; style tips 4–5.5 mm, conspicuously exserted. |
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Phyllaries | 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. |
in 4–8 series, subequal, ± lanceolate, bases appressed, apices ascending, linear to broadly expanded, erose to lacerate or spiny-fringed, spines straight, slender, 2–3 mm, abaxial faces with or without narrow glutinous ridge; apices of inner flexuous, sometimes expanded and erose. |
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Heads | 1–few, in leafy, ± corymbiform arrays. |
several–many, erect, usually in racemiform or spiciform arrays, usually closely subtended by clustered ± leafy bracts. |
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Cypselae | 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. |
brown, 5.5–6.5 mm, apical collars not differentiated; pappi 17–20 mm. |
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2n | = 30, 31, 32, 34. |
= 34. |
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Cirsium ochrocentrum |
Cirsium longistylum |
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Phenology | Flowering summer (Jun–Aug). | |||||
Habitat | Moist soil, roadsides, meadows, forest edges and openings | |||||
Elevation | 1500–2400 m (4900–7900 ft) | |||||
Distribution |
AZ; CA; CO; KS; NE; NM; OK; SD; TX; UT; WY; n Mexico
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MT |
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Discussion | Varieties 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Cirsium longistylum is endemic to the Big Belt, Castle, Elkhorn, and Little Belt ranges of west-central Montana. It is highly variable, and several authors have suggested that it has introgressed with one or more other species (R. J. Moore and C. Frankton 1963; J. M. Poole and B. L. Heidel 1993; S. J. Brunsfeld and C. T. Baldwin, unpubl.). It is closely related to C. hookerianum, and the two probably share a common ancestry or a history of hybrid interactions dating back to the Pleistocene. Cirsium longistylum is perhaps also affected by modern or historic introgression involving C. scariosum var. scariosum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 123. | FNA vol. 19, p. 149. | ||||
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | A. Gray: Mem. Amer. Acad. Arts, n. s. 4: 110. (1849) | R. J. Moore & Frankton: Canad. J. Bot. 41: 1562, plate 1. (1963) | ||||
Web links |