Cirsium arizonicum var. tenuisectum

D. J. Keil

Sida 21: 210. 2004.

Common names: Desert mountains thistle
Treatment appears in FNA Volume 19. Treatment on page 144. Mentioned on page 142, 151.

Stems thinly arachnoid tomentose, ± glabrate, without septate trichomes. Leaf-blades deeply divided, often nearly to the midveins, abaxial faces arachnoid tomentose or sometimes glabrate, without septate trichomes, adaxial thinly arachnoid or glabrate; main marginal spines often stout, 5–30 mm; cauline bases narrowed to truncate or ± clasping, but not or only slightly decurrent. Involucres cylindric to campanulate. Phyllary spines stout, 5–25 mm. Corollas reddish purple, 25–35 mm, tubes 10–13, throats 5–8 mm, lobes 10–13.5 mm; style tips 1–2 mm. 2n = 34 (as C. nidulum).


Phenology: Flowering summer–fall (Jun–Nov).
Habitat: Rocky slopes, drainages, roadsides, pine-oak-juniper woodlands, montane coniferous forests
Elevation: 1500–2800 m

Discussion

Of conservation concern.

Variety tenuisectum occurs in the New York Mountains of southeastern California and the Spring Mountains of southwestern Nevada. The name Cirsium nidulum has long been misapplied to the plants here treated as var. tenuisectum (e.g., P. A. Munz 1959; J. T. Howell 1960b; R. J. Moore and C. Frankton 1974b; D. J. Keil and C. E. Turner 1993). My examination of the type of C. nidulum indicates that the taxon is properly treated as a synonym of C. arizonicum var. arizonicum.

Cirsium eatonii var. clokeyi occurs in close proximity to C. arizonicum var. tenuisectum in the ski area of upper Lee Canyon in the Spring Mountains. I did not see any evidence of hybridization during my brief field survey in that area.

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

glabrate +, tomentose +  and arachnoid +
glabrate +  and arachnoid +
short-tailed +
spineless +  and twisted +
spreading +  and ascending +
innermost +
inconspicuous +
scarious +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.03 cm0.3 mm <br />3.0e-4 m <br />) +
paniculiform +  and corymbiform +
indeterminate +  and determinate +
David J. Keil +
D. J. Keil +
sessile +  and winged-petiolate +
decurrent +
Cnicus arizonicus +
compound +  and simple +
3 cm30 mm <br />0.03 m <br /> (40 cm400 mm <br />0.4 m <br />) +
spinulose;shallowly lobed or divided +
1cm;13cm +
with straight or flexuous spines +  and unarmed +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
? (?) +  and ? (?) +
clasping +  and truncate +
decurrent +  and narrowed +
Desert mountains thistle +
actinomorphic +
reddish purple +
2.5 cm25 mm <br />0.025 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
compressed +  and ovoid +
fertile +  and bisexual +
Calif. +  and Nev. +
1500–2800 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Rocky slopes, drainages, roadsides, pine-oak-juniper woodlands, montane coniferous forests +
indeterminate +
each +  and sessile +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
glabrous +  and arachnoid +
cylindric;campanulate +
1 cm10 mm <br />0.01 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
bristle-tipped +
divided +, lobed +, ovate +  and linear-acuminate +
0.5 cm5 mm <br />0.005 m <br /> (3 cm30 mm <br />0.03 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (3 cm30 mm <br />0.03 m <br />) +
usually lobed +  and dissected +
2-carpellate +
persistent +
1.7 cm17 mm <br />0.017 m <br /> (2.8 cm28 mm <br />0.028 m <br />) +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
Flowering summer–fall (Jun–Nov). +
middle +  and outer +
weakly to strongly +
0.5 cm5 mm <br />0.005 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
papillate +  and smooth +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
inconspicuous +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
Illustrated +
flexuous +  and straight +
erect +  and reflexed +
flattened +  and cylindric +
Slender (?) +  and Stout (?) +
0.1 cm1 mm <br />0.001 m <br /> (3 cm30 mm <br />0.03 m <br />) +
spiny-winged +, simple +  and branched +
ascending +  and erect +
1 +  and several +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Compositae +
Cirsium arizonicum var. tenuisectum +
Cirsium arizonicum +
variety +
cylindric +
expanded +
0.5 cm5 mm <br />0.005 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
bristly-dentate to coarsely +
slender +
0.7 cm7 mm <br />0.007 m <br /> (1.25 cm12.5 mm <br />0.0125 m <br />) +
30 cm300 mm <br />0.3 m <br /> (150 cm1,500 mm <br />1.5 m <br />) +
tree +, vine +, shrub +  and subshrub +
0 cm0 mm <br />0 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +