10. Cirsium lecontei Torrey & A. Gray, Fl. N. Amer. 2: 458. 1843.
Black or Le Conte’s thistle
Carduus lecontei (Torrey & A. Gray) Pollard
Perennials but sometimes appearing biennial, 35–110 cm; taproots, sometimes with root sprouts. Stems 1–few, erect, distal 1/2 nearly naked, loosely arachnoid; branches 0–5(–10), stiffly ascending. Leaves: blades linear to oblong or narrowly elliptic, 15–25 × 1–4 cm, coarsely toothed to shallowly pinnatifid, lobes undivided or coarsely few-toothed, main spines 3–6 mm, abaxial faces often ± glabrate, loosely arachnoid when young, adaxial glabrous or sparingly villous with coarse, multicellular trichomes; basal sometimes absent at flowering, petiolate; principal cauline sessile, progressively reduced distally, bases clasping or ± decurrent; distal cauline few, widely separated, bractlike. Heads borne singly or less commonly 2–5(–10) in open, corymbiform arrays. Peduncles 5–30 cm (elevated above cauline leaves, not subtended by ring of involucre-like bracts. . Involucres broadly cylindric to campanulate, 2.5–4 × 1.5–4 cm, loosely arachnoid, ± glabrate. Phyllaries in 6–10 series, imbricate, ovate or lanceolate (outer) to linear-lanceolate (inner), abaxial faces with prominent glutinous ridge, outer and middle tightly appressed, margins spinulose-serrulate, spines ascending, 0.5–2 mm; apices of inner flat, linear- acuminate. Corollas pink-purple, 22–45 mm, tubes 10–23 mm, throats 8–14 mm, lobes 7–10 mm; style tips 4–5 mm. Cypselae light brown, 5–5.75 mm, apical collars paler than body, ca. 0.75 mm; pappi 20–40 mm. 2n = 28, 32.
Flowering spring–summer (May–Aug). Sandy pinelands of coastal plain, often in damp soil; of conservation concern; 0–150 m; Ala., Fla., La., Miss., N.C., S.C.
Cirsium lecontei occurs on the southern coastal plain. R. J. Moore and C. Frankton (1969) suggested that it originated as a derivative of ancient hybridization between the ancestors of C. horridulum and C. nuttallii. They further suggested a relationship between C. lecontei and C. grahamii of Arizona and hypothesized an ancient dispersal from the southeastern coastal plain to the western cordillera. Although such relationships are possible, I have seen little support for them in my examination of these taxa. I think it is more likely that C. lecontei, C. horridulum, and C. nuttallii originated from a common stock, and that the resemblances between C. lecontei and C. grahamii are a result of convergence.