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Palouse thistle

Hooker's thistle, white thistle

Habit Perennials, 25–120 cm; taproots with horizontal root sprouts. Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 cm; taprooted.
Stems

1–several, erect, thinly gray-tomentose with fine, non-septate trichomes;

branches 0–many, ascending.

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.

Leaves

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.

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.

Peduncles

1–8 cm.

0–8+ cm.

Involucres

hemispheric to campanulate, 2.5–3.5 × 2–4 cm, glabrous or loosely floccose.

(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.

Corollas

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.

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.

Phyllaries

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.

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.

Heads

borne singly and terminal on main stems and branches or few from distal axils in corymbiform or paniculiform arrays.

1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays.

Cypselae

brown, 5–6 mm, apical collars yellowish, 0.5–1 mm;

pappi 18–22 mm.

dark brown, 5–6.5 mm, apical collars not differentiated;

pappi 18–22 mm.

2n

= 22, 26.

= 34.

Cirsium brevifolium

Cirsium hookerianum

Phenology Flowering summer (Jun–Oct). Flowering summer (Jun–Sep).
Habitat Palouse prairie Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows
Elevation 600–1300 m (2000–4300 ft) 600–2900 m (2000–9500 ft)
Distribution
from FNA
ID; OR; WA
[WildflowerSearch map]
[BONAP county map]
from FNA
ID; MT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

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.)

Source FNA vol. 19, p. 124. FNA vol. 19, p. 148.
Parent taxa Asteraceae > tribe Cardueae > Cirsium Asteraceae > tribe Cardueae > Cirsium
Sibling taxa
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, C. horridulum, C. hydrophilum, C. inamoenum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ochrocentrum, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. scariosum, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevifolium, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. horridulum, C. hydrophilum, C. inamoenum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ochrocentrum, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. scariosum, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
Synonyms C. palousense C. kelseyi
Name authority Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 421. (1841) Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 418. (1841)
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