Cirsium hookerianum

Nuttall

Trans. Amer. Philos. Soc., n. s. 7: 418. 1841.

Common names: Hooker’s or white thistle
Endemic
Synonyms: Cirsium kelseyi (Rydberg) Petrak
Treatment appears in FNA Volume 19. Treatment on page 148. Mentioned on page 100, 101, 102, 121, 126, 149.

Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 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. 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. Heads 1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays. Peduncles 0–8+ 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. 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. 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. Cypselae dark-brown, 5–6.5 mm, apical collars not differentiated; pappi 18–22 mm. 2n = 34.


Phenology: Flowering summer (Jun–Sep).
Habitat: Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows
Elevation: 600–2900 m

Distribution

V19-137-distribution-map.gif

Alta., B.C., Idaho, Mont., Wash., Wyo.

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.

Selected References

None.

Lower Taxa

None.

"fine" is not a number."often narrower" is not a number.

... more about "Cirsium hookerianum"
glabrate +, glabrous +, less villous +  and tomentose +
tomentose +, villous +, glabrous +  and thinly arachnoid +
short-tailed +
spineless +  and twisted +
dentate +, entire +  and spine-tipped +
stiffly spreading +  and ascending +
innermost +
scarious +
not differentiated +
corymbiform +, paniculiform +, subcapitate +, spiciform +  and racemiform +
indeterminate +  and determinate +
David J. Keil +
Nuttall +
sessile +, winged-petiolate +  and spiny +
short-decurrent +
non-pigmented +
decurrent +
Asteraceae tribe Cynareae +
compound +  and simple +
5 cm50 mm <br />0.05 m <br /> (25 cm250 mm <br />0.25 m <br />) +
subentire;coarsely dentate or deeply pinnatifid +
1cm;8cm +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
Hooker’s or white thistle +
actinomorphic +
pink +, ochroleucous +  and white +
2 cm20 mm <br />0.02 m <br /> (2.8 cm28 mm <br />0.028 m <br />) +
compressed +  and ovoid +
fertile +  and bisexual +
simple;sparingly short-branched +
Alta. +, B.C. +, Idaho +, Mont. +, Wash. +  and Wyo. +
600–2900 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows +
corymbiform +, branched +  and racemiform +
crowded +  and or +
indeterminate +
each +  and sessile +
2 cm20 mm <br />0.02 m <br /> (3.3 cm33 mm <br />0.033 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
bristle-tipped +
lobed +, spiny-dentate +, lance-oblong +  and broadly triangular +
0.2 cm2 mm <br />0.002 m <br /> (1 cm10 mm <br />0.01 m <br />) +
entire +  and dentate +
usually lobed +  and dissected +
2-carpellate +
persistent +
1.8 cm18 mm <br />0.018 m <br /> (2.2 cm22 mm <br />0.022 m <br />) +
0 cm0 mm <br />0 m <br /> (8 cm80 mm <br />0.08 m <br />) +
Flowering summer (Jun–Sep). +
middle +  and outer +
papillate +  and smooth +
sessile +  and winged-petiolate +
Trans. Amer. Philos. Soc., n. s. +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
straight +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
spiny-winged +, simple +  and branched +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.3 cm3 mm <br />0.003 m <br /> (0.55 cm5.5 mm <br />0.0055 m <br />) +
Cirsium kelseyi +
Cirsium hookerianum +
species +
cylindric +
expanded +
0.65 cm6.5 mm <br />0.0065 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
bristly-dentate to coarsely +
septate +  and jointed +
arachnoid +, tomentose +, felted +  and glabrate +
slender +
1 cm10 mm <br />0.01 m <br /> (1.3 cm13 mm <br />0.013 m <br />) +
perennial +  and biennial +
20 cm200 mm <br />0.2 m <br /> (150 cm1,500 mm <br />1.5 m <br />) +
tree +, vine +, shrub +  and subshrub +