Cirsium scariosum var. coloradense

(Rydberg) D. J. Keil

Sida 21: 215. 2004.

Common names: Colorado thistle
Endemic
Basionym: Carduus coloradensis Rydberg Bull. Torrey Bot. Club 32: 132. 1905
Synonyms: Cirsium coloradense (Rydberg) Cockerell ex Daniels Cirsium erosum (Rydberg) K. Schumann Cirsium tioganum var. coloradense (Rydberg) Dorn
Treatment appears in FNA Volume 19. Treatment on page 156. Mentioned on page 121, 125, 155, 157.

Plants usually erect, caulescent (rarely acaulescent), 20–150 cm. Stems usually simple, proximally unbranched, very leafy, ± villous with septate trichomes and/or thinly arachnoid tomentose, often glabrate. Leaves: blades oblanceolate or narrowly elliptic, pinnately lobed, longer spines ± stout, usually 1 cm or shorter, abaxial faces glabrous to thinly gray-tomentose, adaxial glabrous; distal narrow, firm, green throughout or unpigmented proximally. Heads 3–10+, ± sessile or pedunculate, usually in spiciform or racemiform arrays, subtended by ± reduced bractlike distal leaves that often do not overtop the heads. Peduncles 0–18 cm. Involucres 2–3 cm. Phyllaries: outer and mid lanceolate to narrowly ovate, spines slender to stout, 1–5 mm; apices of inner acuminate and entire or serrate, or abruptly expanded into scarious, erose-toothed appendages. Corollas white (rarely purple), 22–29 mm, tubes 11–16 mm, throats 4–5 mm, lobes 6–9.5 mm; style tips 4–6 mm. Cypselae 4–6 mm; pappi 18–25 mm. 2n = 34, 36? (as C. foliosum).


Phenology: Flowering summer (Jun–Sep).
Habitat: Wet soil, forests, meadows, roadsides
Elevation: 1900–2500 m

Distribution

V19-152-distribution-map.gif

Ariz., Colo., N.Mex., Utah, Wyo.

Discussion

Variety coloradense is common in the mountains of southern and central Colorado with outlying populations in northern New Mexico, northeastern Arizona, central Utah, and southeastern Wyoming. In Colorado it is largely allopatric with the usually acaulescent var. americanum. Some plants from the White Mountains and San Francisco Peaks of Arizona and from Gunnison County, Colorado, approach var. thorneae in having deeply divided, extremely spiny distal leaves that overtop the heads. Putative hybrids between var. coloradense and Cirsium grahamii have been documented in Apache County, Arizona, and between var. coloradense and C. undulatum in Las Animas County, Colorado.

Selected References

None.

Lower Taxa

None.

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

glabrous +  and thinly gray-tomentose +
short-tailed +
spineless +  and twisted +
serrate +  and entire +
erect +  and spreading +
innermost +
expanded +
scarious +
erose-toothed +
racemiform +  and spiciform +
indeterminate +  and determinate +
David J. Keil +
(Rydberg) D. J. Keil +
winged-petiolate +  and sessile +
decurrent +
Carduus coloradensis +
compound +  and simple +
linear to elliptic +
5 cm50 mm <br />0.05 m <br /> (20 cm200 mm <br />0.2 m <br />) +
lobed;elliptic;oblanceolate +
3cm;7cm +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
? (?) +  and ? (?) +
Colorado thistle +
actinomorphic +
2.2 cm22 mm <br />0.022 m <br /> (2.9 cm29 mm <br />0.029 m <br />) +
light +  and dark-brown +
compressed +  and ovoid +
fertile +  and bisexual +
green throughout or unpigmented +
Ariz. +, Colo. +, N.Mex. +, Utah +  and Wyo. +
1900–2500 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Wet soil, forests, meadows, roadsides +
pedunculate +  and sessile +
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 cm20 mm <br />0.02 m <br /> (3 cm30 mm <br />0.03 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 +
bristle-tipped +
lobed +, spinose-dentate +, linear-lanceolate +  and broadly triangular +
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 +
1.8 cm18 mm <br />0.018 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
0 cm0 mm <br />0 m <br /> (18 cm180 mm <br />0.18 m <br />) +
Flowering summer (Jun–Sep). +
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 +
erect +  and spreading +
flattened +
Slender (?) +  and Stout (?) +
0.1 cm1 mm <br />0.001 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
leafy +, unbranched +  and simple +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.4 cm4 mm <br />0.004 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
Cirsium coloradense +, Cirsium erosum +  and Cirsium tioganum var. coloradense +
Cirsium scariosum var. coloradense +
Cirsium scariosum +
variety +
cylindric +
expanded +
0.4 cm4 mm <br />0.004 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
tipped +  and spineless +
scabro-denticulate +  and narrowed +
expanded +
bristly-dentate to coarsely +
slender +
1.1 cm11 mm <br />0.011 m <br /> (1.6 cm16 mm <br />0.016 m <br />) +
taprooted +, caulescent +  and acaulescent +
perennial +  and biennial +
0 cm0 mm <br />0 m <br /> (200 cm2,000 mm <br />2 m <br />) +