Cirsium hookerianum |
Cirsium rhothophilum |
|
---|---|---|
Hooker's thistle, white thistle |
surf thistle |
|
Habit | Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 cm; taprooted. | Biennials or short-lived, usually monocarpic perennials, 10–100 cm; taprooted with simple or branched caudices. |
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, spreading to erect, bushlike or forming low rounded mounds, gray-tomentose with appressed feltlike trichomes; branches 0–several, inclined to ascending, stiff. |
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. |
blades elliptic to ovate, 10–25 cm, strongly undulate, usually broadly pinnatifid, lobes entire or coarsely few-toothed or -lobed, main spines abrupt, 1–4 mm, faces gray-white-tomentose with appressed feltlike, non-septate trichomes; basal present or withered at flowering, winged-petiolate; principal cauline well distributed, winged-petiolate to sessile, gradually reduced, bases clasping with expanded auricles; distal reduced, spines to 8 mm. |
Peduncles | 0–8+ cm. |
0–7 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 or campanulate, 3–4 × 4–6 cm, densely arachnoid. |
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. |
white to pale yellow, 20–34 mm, tubes 11–15 mm, throats 5–8 mm, lobes 5–8 mm; style tips 3–4 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 8–10 series, imbricate, linear, abaxial faces without glutinous ridge; outer and mid bases short- appressed, margins spiny-ciliate, apices long, spreading to erect, spines straight, 2–5 mm; apices of inner flattened or spine-tipped, serrate to scabrid, sometimes pectinately fringed. |
Heads | 1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays. |
1–many, erect, terminal on branches in subcapitate to congested, corymbiform arrays, closely subtended by clustered, ± leafy bracts. |
Cypselae | dark brown, 5–6.5 mm, apical collars not differentiated; pappi 18–22 mm. |
light–brown to black, 5–7 mm, apical collars whitish, 0.2–0.3 mm; pappi 15–25 mm. |
2n | = 34. |
= 34. |
Cirsium hookerianum |
Cirsium rhothophilum |
|
Phenology | Flowering summer (Jun–Sep). | Flowering mostly spring–summer (Apr–Aug), occasionally year round. |
Habitat | Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows | Coastal dunes and bluffs |
Elevation | 600–2900 m (2000–9500 ft) | 0–20 m (0–100 ft) |
Distribution |
ID; MT; WA; WY; AB; BC
|
CA |
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.) |
Of conservation concern. Cirsium rhothophilum is endemic to the dunes of southern San Luis Obispo and northern Santa Barbara counties. It rarely forms hybrids with C. occidentale var. occidentale and C. scariosum var. citrinum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 148. | FNA vol. 19, p. 161. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | C. kelseyi | Carduus maritima |
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 418. (1841) | S. F. Blake: J. Wash. Acad. Sci. 21: 336. (1931) |
Web links |