Flora of North America species comparison

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Cirsium horridulum var. megacanthum
Photo is of parent taxon

bigspine thistle
Habit 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.
Involucres

4–5 × 5–8 cm, glabrous.
Corollas

pink to purple.
Phyllaries

outer and middle bodies scabridulous or minutely spinulose, marginal spinules usually 1 mm or shorter.
Heads

10–20.
2n

= 32, 34.

Cirsium horridulum var. megacanthum
Phenology Flowering spring (Mar–Jun).
Habitat Meadows, pastures, roadsides, forest openings, low ground, often in damp soil
Elevation 0–100 m (0–300 ft)
Distribution
from FNA
AL; AR; FL; LA; MS; OK; TX
[BONAP county map]
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.”

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 115.
Parent taxa Asteraceae > tribe Cardueae > Cirsium > Cirsium horridulum
Sibling taxa
C. horridulum var. horridulum, C. horridulum var. vittatum
Synonyms C. megacanthum
Name authority (Nuttall) D. J. Keil: Sida 21: 214. (2004)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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