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Photo is of parent taxon

horrid thistle, yellow thistle

Habit Plants 15–180 cm.
Stems

densely tomentose.

Leaves

blades oblanceolate or oblong-elliptic, 10–30 cm, shallowly to deeply pinnatifid, main spines mostly 5–10 mm, abaxial faces loosely tomentose.

Involucres

4–5 × 5–7 cm, ± densely tomentose.

Corollas

yellow or crimson to red-purple.

Phyllaries

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

Heads

1–10.

2n

= 32, 34.

Cirsium horridulum var. horridulum

Phenology Flowering winter–spring (Apr–Jun).
Habitat Fields, meadows, pinelands, roadsides, often weedy, often in damp soil
Elevation 0–300 m (0–1000 ft)
Distribution
from FNA
AL; CT; DE; FL; GA; LA; MA; MD; ME; MS; NC; NH; NJ; NY; PA; RI; SC; TN; TX; VA
[BONAP county map]
Discussion

Variety horridulum occurs on the Atlantic and Gulf coastal plains fom southern Maine to Florida and west to eastern Texas and into the piedmont in much of the southeastern United States. Artificial hybrids have been produced between var. horridulum and Cirsium repandum (R. J. Moore and C. Frankton 1969), and natural hybrids with C. pumilum var. pumilum have been reported.

(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. megacanthum, C. horridulum var. vittatum
Synonyms Carduus spinosissimus, Carduus horridulum var. elliottii
Name authority unknown
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