Cirsium horridulum var. megacanthum

(Nuttall) D. J. Keil

Sida 21: 214. 2004.

Common names: Bigspine thistle
IllustratedEndemic
Basionym: Cirsium megacanthum Nuttall Trans. Amer. Philos. Soc., n. s. 7: 421. 1841 (as Circium)
Treatment appears in FNA Volume 19. Treatment on page 115. Mentioned on page 114.

Plants 100–250 cm. Stems glabrous to sparsely tomentose. Leaves: blades oblanceolate or oblongelliptic, 20–40 cm, shallowly to deeply pinnatifid, main spines 10–30 mm, abaxial faces glabrous or nearly so. Heads 10–20. Involucres 4–5 × 5–8 cm, glabrous. Phyllaries: outer and middle bodies scabridulous or minutely spinulose, marginal spinules usually 1 mm or shorter. Corollas pink to purple. 2n = 32, 34.


Phenology: Flowering spring (Mar–Jun).
Habitat: Meadows, pastures, roadsides, forest openings, low ground, often in damp soil
Elevation: 0–100 m

Distribution

V19-64-distribution-map.gif

Ala., Ark., Fla., La., Miss., Okla., Tex.

Discussion

Variety megacanthum occurs on the coastal plain and lower piedmont from northern Florida to eastern Texas and southeastern Oklahoma. Nuttall described this thistle as “one of the most terribly armed plants in the genus.”

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

nearly +  and glabrous +
glabrous +  and more or less densely villous +
short-tailed +
spineless +  and twisted +
dentate +, entire +  and spine-tipped +
erect +  and spreading +
innermost +
scarious +
subcapitate +  and corymbiform +
indeterminate +  and determinate +
David J. Keil +
(Nuttall) D. J. Keil +
winged-petiolate +
auriculate-clasping +
tapered +
Cirsium megacanthum +
compound +  and simple +
10 cm100 mm <br />0.1 m <br /> (40 cm400 mm <br />0.4 m <br />) +
pinnatifid;oblongelliptic;oblanceolate +
20 cm200 mm <br />0.2 m <br /> (40 cm400 mm <br />0.4 m <br />) +
2cm;10cm +
reddish-tinged +
10-nerved or 20-nerved +  and rugose +
spreading;ascending +
tawny +  and white +
Bigspine thistle +
actinomorphic +
pink +  and purple +
3 cm30 mm <br />0.03 m <br /> (4.7 cm47 mm <br />0.047 m <br />) +
straw-colored +  and tan +
compressed +  and ovoid +
fertile +  and bisexual +
Ala. +, Ark. +, Fla. +, La. +, Miss. +, Okla. +  and Tex. +
0–100 m +
gray-canescent +  and glabrous +
perennating +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Meadows, pastures, roadsides, forest openings, low ground, often in damp soil +
indeterminate +
each +  and sessile +
4 cm40 mm <br />0.04 m <br /> (5 cm50 mm <br />0.05 m <br />) +
hemispheric;campanulate +
5 cm50 mm <br />0.05 m <br /> (8 cm80 mm <br />0.08 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
bristle-tipped +
lobed +  and spiny-dentate +
1 cm10 mm <br />0.01 m <br /> (3 cm30 mm <br />0.03 m <br />) +
entire +  and dentate +
setulose-ciliolate +
usually lobed +  and dissected +
2-carpellate +
persistent +
2.5 cm25 mm <br />0.025 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
0 cm0 mm <br />0 m <br /> (5 cm50 mm <br />0.05 m <br />) +
Flowering spring (Mar–Jun). +
middle +  and outer +
papillate +  and smooth +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
Illustrated +  and Endemic +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
spiny-winged +, simple +  and branched +
1 +  and several +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
Compositae +
Cirsium horridulum var. megacanthum +
Cirsium horridulum +
variety +
cylindric +
expanded +
0.6 cm6 mm <br />0.006 m <br /> (1 cm10 mm <br />0.01 m <br />) +
bristly-dentate to coarsely +
slender +
1.1 cm11 mm <br />0.011 m <br /> (3 cm30 mm <br />0.03 m <br />) +
perennial +  and biennial +
appressed-ascending +
15 cm150 mm <br />0.15 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +