Cirsium horridulum var. megacanthum

(Nuttall) D. J. Keil

Sida 21: 214. 2004. 2004

Common names: Bigspine thistle
IllustratedEndemic
Basionyms: 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 oblong-elliptic, 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.

David J. Keil +
(Nuttall) D. J. Keil +
Cirsium megacanthum +
Bigspine thistle +
Ala. +, Ark. +, Fla. +, La. +, Miss. +, Okla. +  and Tex. +
0–100 m +
Meadows, pastures, roadsides, forest openings, low ground, often in damp soil +
Flowering spring (Mar–Jun). +
Illustrated +  and Endemic +
Compositae +
Cirsium horridulum var. megacanthum +
Cirsium horridulum +
variety +