Cirsium hookerianum |
Cirsium brevifolium |
|
---|---|---|
Hooker's thistle, white thistle |
Palouse thistle |
|
Habit | Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 cm; taprooted. | Perennials, 25–120 cm; taproots with horizontal root sprouts. |
Stems | usually 1 and erect, less commonly several and ascending, simple to sparingly short-branched in distal 1/2, variably villous with jointed trichomes, and/or finely arachnoid, or ± glabrate; branches on distal stems 0–many, short, ascending. |
1–several, erect, thinly gray-tomentose with fine, non-septate trichomes; branches 0–many, ascending. |
Leaves | blades linear-oblong to elliptic, 5–25 × 1–8 cm, subentire to coarsely dentate or deeply pinnatifid, lobes lance-oblong to broadly triangular, spinulose to spiny-dentate or shallowly lobed, main spines 2–10 mm, abaxial faces usually ± densely gray- or white-tomentose with felted arachnoid trichomes, ± villous to tomentose along major veins with septate trichomes, sometimes glabrous or glabrate, adaxial ± green, glabrous to thinly arachnoid, often ± villous or tomentose 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; distal ± reduced, often narrower than proximal, sometimes with non-pigmented bases, sometimes pectinately spiny. |
oblanceolate or elliptic, 15–45 × 2–10 cm, unlobed and merely spinulose to dentate or deeply pinnatifid, lobes well separated, linear to triangular-ovate, merely spinulose to few toothed or lobed near base, margins often revolute, main spines 2–3(–6) mm, abaxial faces densely gray-tomentose, adaxial green, thinly tomentose or ± glabrate; basal often present at flowering, narrowly winged-petiolate; principal cauline well distributed, gradually reduced distally, bases of proximal cauline winged-petiolate or sessile, bases of distal cauline expanded and ± clasping, margins sometimes spinier than those of proximal; distalmost cauline becoming bractlike, often unlobed or less deeply divided than proximal. |
Peduncles | 0–8+ cm. |
1–8 cm. |
Involucres | (green or often purplish), broadly ovoid, 2–3.3 × 1.5–4 cm, loosely to densely villous with septate trichomes to tomentose and/or arachnoid. |
hemispheric to campanulate, 2.5–3.5 × 2–4 cm, glabrous or loosely floccose. |
Corollas | white, ochroleucous, or occasionally pink, 20–28 mm, tubes 10–13 mm, throats 6.5–9 mm, lobes 5–7 mm; style tips 3–5.5 mm. |
creamy white, rarely lavender-tinged, 22–28 mm, tubes 8–13 mm, throats 7–11 mm, lobes 4–6 mm; style tips 5–6 mm. |
Phyllaries | in 4–8 series, imbricate to subequal, bases short-appressed, entire, abaxial faces with or without narrow glutinous ridge, apices stiffly spreading to ascending, linear, long, plane, spines straight, slender, 3–5 mm; apices of inner flexuous, sometimes expanded and erose. |
in 6–10 series, strongly imbricate, greenish to brown, ovate to lanceolate (outer) to linear (inner), abaxial faces with prominent glutinous ridge; outer and middle appressed, bodies entire, spines abruptly spreading, fine, 2–3(–5) mm; apices of inner commonly flexuous or reflexed, flat, scarious. |
Heads | 1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays. |
borne singly and terminal on main stems and branches or few from distal axils in corymbiform or paniculiform arrays. |
Cypselae | dark brown, 5–6.5 mm, apical collars not differentiated; pappi 18–22 mm. |
brown, 5–6 mm, apical collars yellowish, 0.5–1 mm; pappi 18–22 mm. |
2n | = 34. |
= 22, 26. |
Cirsium hookerianum |
Cirsium brevifolium |
|
Phenology | Flowering summer (Jun–Sep). | Flowering summer (Jun–Oct). |
Habitat | Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows | Palouse prairie |
Elevation | 600–2900 m (2000–9500 ft) | 600–1300 m (2000–4300 ft) |
Distribution |
ID; MT; WA; WY; AB; BC
|
ID; OR; WA
|
Discussion | Cirsium hookerianum occurs from the Canadian Coast Ranges of British Columbia east to the northern Cascade Range and the northern Rocky Mountains. The relationship between C. hookerianum, C. kelseyi, which I have tentatively included in C. hookerianum, and C. longistylum needs further investigation. A case could be made for including all three in an expanded concept of C. hookerianum, but more investigation of the variation patterns is needed before this is done. Certainly C. kelseyi is better treated within or as a close ally of C. hookerianum than in C. scariosum (var. scariosum), where R. J. Moore and C. Frankton (1974) synonymized it. Cirsium hookerianum is known to hybridize with C. undulatum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Cirsium brevifolium occurs in the Palouse prairie region of eastern Washington, eastern Oregon, and western Idaho. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 148. | FNA vol. 19, p. 124. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | C. kelseyi | C. palousense |
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 418. (1841) | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 421. (1841) |
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