Cirsium pulcherrimum var. aridum

(Dorn) D. J. Keil

Sida 21: 215. 2004.

Common names: Cedar Rim thistle
EndemicConservation concern
Basionym: Cirsium aridum Dorn Vasc. Pl. Wyoming ed. 2, 304, plate [p. 305]. 1992
Treatment appears in FNA Volume 19. Treatment on page 126.

Stems often clustered from branched rootstock, 15–40 cm, bases not thickened. Adaxial leaf faces gray to white-tomentose. Heads 1–4, in compact arrays. Cypselae without stramineous apical collars.


Phenology: Flowering summer (Jun–Aug).
Habitat: Barren slopes in shallow, stony soil in very open, arid grasslands
Elevation: 2000–2200 m

Discussion

Of conservation concern.

In describing variety aridum, Dorn suggested that it “seems to belong to the C. hookerianum group,” but I fail to see this relationship. Its affinities clearly lie with Cirsium pulcherrimum. It is usually differentiable from var. pulcherrimum by the characters above, but it grows and intergrades with var. pulcherrimum on the Sweetwater Plateau in Fremont County. W. Fertig (unpubl.) has studied the ecology and distribution of var. aridum [as C. aridum] and the very similar pubescent forms of var. pulcherriumum [as C. pulcherrimum].

Variety aridum occurs in scattered localities on barren hills in Carbon, Fremont, and Sweetwater counties. It is a rare taxon, but it has not received official recognition by governmental agencies. However it is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Selected References

None.

Lower Taxa

None.

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

gray +  and white +
villous +, glabrate +  and arachnoid-tomentose +
gray-tomentose +, less commonly +  and glabrous +
short-tailed +
spineless +  and twisted +
dentate +, entire +  and spine-tipped +
erect +  and spreading +
innermost +
scarious +
spreading +  and stiffly ascending +
linear-lanceolate +  and acicular +
indeterminate +  and determinate +
flat-topped +
David J. Keil +
(Dorn) D. J. Keil +
winged-petiolate +
decurrent +
not thickened +
Cirsium aridum +
compound +  and simple +
5 cm50 mm <br />0.05 m <br /> (25 cm250 mm <br />0.25 m <br />) +
unlobed;linear;oblong oblanceolate or elliptic +
0.6cm;7cm +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
? (?) +  and ? (?) +
deep-seated +
Cedar Rim thistle +
actinomorphic +
pink +  and purple +
1.8 cm18 mm <br />0.018 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
tan +  and dark-brown +
compressed +  and ovoid +
fertile +  and bisexual +
2000–2200 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Barren slopes in shallow, stony soil in very open, arid grasslands +
in 2-3-headed clusters in more or less congested flat-topped or racemiform arrays +  and singly +
indeterminate +
each +  and sessile +
1.8 cm18 mm <br />0.018 m <br /> (2.7 cm27 mm <br />0.027 m <br />) +
glabrate +  and arachnoid-tomentose +
ovoid;campanulate +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
sessile +  and petiolate +
white-tomentose +
cauline +  and basal +
bristle-tipped +
ascending-spreading;retrorse +
linear +  and triangular-ovate +
slender +
lobed +, few +  and dentate +
0.2 cm2 mm <br />0.002 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
usually lobed +  and dissected +
2-carpellate +
persistent +
1.4 cm14 mm <br />0.014 m <br /> (1.6 cm16 mm <br />0.016 m <br />) +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
Flowering summer (Jun–Aug). +
middle +  and outer +
weakly to strongly +
papillate +  and smooth +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
Endemic +  and Conservation concern +
ascending +  and spreading +
flattened +
0.2 cm2 mm <br />0.002 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
spiny-winged +, simple +  and branched +
ascending +  and erect +
1 +  and few +
15 cm150 mm <br />0.15 m <br /> (40 cm400 mm <br />0.4 m <br />) +
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 />) +
Compositae +
deep-seated +
Cirsium pulcherrimum var. aridum +
Cirsium pulcherrimum +
variety +
cylindric +
expanded +
0.55 cm5.5 mm <br />0.0055 m <br /> (0.75 cm7.5 mm <br />0.0075 m <br />) +
bristly-dentate to coarsely +
slender +
0.7 cm7 mm <br />0.007 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
60 cm600 mm <br />0.6 m <br /> (90 cm900 mm <br />0.9 m <br />) +
15 cm150 mm <br />0.15 m <br /> (60 cm600 mm <br />0.6 m <br />) +
tree +, vine +, shrub +  and subshrub +
1.5 cm15 mm <br />0.015 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +