Cirsium hookerianum |
Cirsium nuttallii |
|
---|---|---|
Hooker's thistle, white thistle |
Nuttall's thistle |
|
Habit | Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 cm; taprooted. | Biennials, 20–350 cm; taprooted. |
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. |
usually single, erect, glabrous or villous with septate trichomes; branches few–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. |
blades narrowly to broadly elliptic, (10–)15–60 × (2–)5–15 cm, thin, ± flexible, deeply pinnatifid, lobes narrow, spreading, coarsely dentate or lobed, main spines 2–5 mm, abaxial faces thinly tomentose but often wholly glabrate in age, adaxial glabrous or sparsely villous with septate trichomes; basal often absent at flowering, petioles slender, winged, bases tapered; principal cauline becoming sessile and gradually reduced distally, bases spiny-lobed, sometimes decurrent; distal reduced to linear bracts. |
Peduncles | 0–8+ cm. |
1–15 cm, essentially naked (not overtopped by crowded distal leaves). |
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, 1.5–2.5 × 1–2.5 cm, thinly arachnoid or glabrate. |
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 pink, lavender, or purple, 17–25 mm, tubes 5–11 mm, throats 4–7 mm (noticeably wider than tubes), lobes 5–7 mm; style tips 3–4.5 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, green or brownish, ovate or elliptic (outer) to linear-lanceolate (inner), abaxial faces with narrow glutinous ridge; outer and middle appressed, bodies entire, spines abruptly spreading, slender, 1–2(–3) mm; apices of inner often flexuous, flat, attenuate. |
Heads | 1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays. |
few–many, in open corymbiform or paniculiform arrays. |
Cypselae | dark brown, 5–6.5 mm, apical collars not differentiated; pappi 18–22 mm. |
dark brown, 3–4 mm, apical collars stramineous, 0.5 mm; pappi 17–21 mm (longer bristles shorter than corollas). |
2n | = 34. |
= 24, 26, 28. |
Cirsium hookerianum |
Cirsium nuttallii |
|
Phenology | Flowering summer (Jun–Sep). | Flowering summer (Jun–Aug). |
Habitat | Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows | Roadsides, ditches, woodlands, usually in damp soil |
Elevation | 600–2900 m (2000–9500 ft) | 0–100 m (0–300 ft) |
Distribution |
ID; MT; WA; WY; AB; BC
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AL; FL; GA; LA; MS; NC; SC; TX; VA
|
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 nuttallii occurs on the southern coastal plain from southeastern Virginia to southern Florida and west to eastern Louisiana. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 148. | FNA vol. 19, p. 119. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | C. kelseyi | Carduus glaber, Carduus nuttallii |
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 418. (1841) | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 6: 651. (1838) |
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