Cirsium scariosum var. robustum

D. J. Keil

Sida 21: 215. 2004.

Common names: Shasta Valley thistle
Treatment appears in FNA Volume 19. Treatment on page 159. Mentioned on page 155.

Plants caulescent, 25–70 cm. Stems (1) often very stout, branched distally or throughout, leafy, glabrous, villous with septate trichomes, or arachnoid-tomentose. Leaves oblanceolate to elliptic, deeply pinnately lobed, longer spines slender or stout, usually 1 cm or shorter, abaxial thinly to densely arachnoid-tomentose, villous with septate trichomes along midveins, adaxial villous with septate trichomes or thinly arachnoid-tomentose. Heads 3–many, evidently pedunculate, in corymbiform or subcapitate arrays at stem tips (in age clustered axillary heads sometimes developing), subtended and ± overtopped by distal leaves or these ± reduced. Involucres 2.5–4 cm. Phyllaries: outer and mid lanceolate to ovate, spines slender to ± broad and flat, 1–6 mm; apices of inner linear-acuminate or more commonly expanded as scarious, erose-toothed appendages, often contorted. Corollas white, 30–36 mm, tubes 14–22 mm, throats 7–12 mm, lobes 5–10 mm; style tips 6–8 mm. Cypselae 4–6.5 mm; pappi 22–32 mm.


Phenology: Flowering summer (Jun–Jul).
Habitat: Wet ground, meadows, pastures, marshes
Elevation: 900–1900 m

Discussion

Variety robustum is known only from northern California (Siskiyou County) and south central Oregon (Klamath and Lake counties). It differs from var. scariosum in its larger, evidently pedunculate heads.

Selected References

None.

Lower Taxa

None.

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

glabrate +, villous +, glabrous or +  and thinly densely tomentose +
glabrescent +, tomentose +  and arachnoid +
short-tailed +
spineless +  and twisted +
dentate +, entire +  and spine-tipped +
erect +  and spreading +
innermost +
expanded +
scarious +
erose-toothed +
subcapitate +, racemiform +  and spiciform +
indeterminate +  and determinate +
David J. Keil +
D. J. Keil +
winged-petiolate +  and sessile +
decurrent +
Asteraceae tribe Cynareae +
compound +  and simple +
linear to elliptic +
5 cm50 mm <br />0.05 m <br /> (20 cm200 mm <br />0.2 m <br />) +
plane;strongly undulate unlobed or +
3cm;7cm +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
? (?) +  and ? (?) +
Shasta Valley thistle +
actinomorphic +
3 cm30 mm <br />0.03 m <br /> (3.6 cm36 mm <br />0.036 m <br />) +
light +  and dark-brown +
compressed +  and ovoid +
fertile +  and bisexual +
Calif. +  and Oreg. +
900–1900 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Wet ground, meadows, pastures, marshes +
pedunculate +
crowded +  and singly +
indeterminate +
each +  and sessile +
2 cm20 mm <br />0.02 m <br /> (4 cm40 mm <br />0.04 m <br />) +
glabrate +  and arachnoid +
ovoid;hemispheric +
2.5 cm25 mm <br />0.025 m <br /> (4 cm40 mm <br />0.04 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (6 cm60 mm <br />0.06 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
lobed;oblanceolate;elliptic +
bristle-tipped +
lobed +, spinose-dentate +, linear-lanceolate +  and broadly triangular +
adaxial +  and abaxial +
arachnoid-tomentose +  and villous +
stout +  and slender +
1 cm10 mm <br />0.01 m <br /> (?) +
0.2 cm2 mm <br />0.002 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
entire +  and dentate +
scarious-fringed +  and entire +
rounded +
2-carpellate +
white +  and tan +
persistent +
2.2 cm22 mm <br />0.022 m <br /> (3.2 cm32 mm <br />0.032 m <br />) +
0 cm0 mm <br />0 m <br /> (10 cm100 mm <br />0.1 m <br />) +
Flowering summer (Jun–Jul). +
middle +  and outer +
weakly to strongly +
short-caulescent +  and acaulescent +
papillate +  and smooth +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
Illustrated +
erect +  and spreading +
flattened +
0.1 cm1 mm <br />0.001 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
leafy +  and branched +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.6 cm6 mm <br />0.006 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
Cirsium hookerianum var. scariosum +
Cirsium scariosum var. robustum +
Cirsium scariosum +
variety +
cylindric +
expanded +
0.7 cm7 mm <br />0.007 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
tipped +  and spineless +
scabro-denticulate +  and narrowed +
expanded +
bristly-dentate to coarsely +
slender +
1.4 cm14 mm <br />0.014 m <br /> (2.2 cm22 mm <br />0.022 m <br />) +
taprooted +, caulescent +  and acaulescent +
perennial +  and biennial +
0 cm0 mm <br />0 m <br /> (200 cm2,000 mm <br />2 m <br />) +