Cirsium texanum

Annuals or biennials, 20-200 cm; taprooted. Stems usually single, erect, tomentose to ± glabrate; branches 0-many, usually restricted to distal part, ascending. Leaves: blades oblong to elliptic, 7-30 × 2-12 cm, unlobed and merely spinulose to irregularly dentate or shallowly to deeply pinnatifid, lobes ± triangular, separated by narrow to wide sinuses, sometimes coarsely dentate or lobed proximally, obtuse to acute, main spines slender to stout, 1-5 mm, abaxial faces arachnoid tomentose, adaxial glabrous or thinly arachnoid; basal often absent at flowering, petioles slender, ± winged; cauline progressively reduced, proximal petiolate, mid and distal broadly sessile, bases ± auriculate-clasping or decurrent 1-3 cm; distalmost linear to lanceolate, bractlike, irregularly dentate or shallowly lobed. Heads 1. many, in openly paniculiform arrays. Peduncles slender, 3-30 cm (not overtopped by crowded distal leaves. . Involucres ovoid to hemispheric, 1.5-2 × 1.5-2 cm, thinly arachnoid, glabrate. Phyllaries in 8-10 series, imbricate, green, lanceolate (outer) to linear (inner), abaxial faces with prominent glutinous ridge; outer and middle appressed, bodies entire, acute, spines spreading, slender, 1-5 mm; apices of inner often flexuous, flat, scabrid-ciliolate, acuminate. Corollas white to pink-purple, 20-25 mm, tubes 7-10 mm, throats 6-8 mm (noticeably wider than tubes. , lobes 4-7 mm; style tips 3-4 mm. Cypselae brown, 3-5 mm, apical collars not differentiated; pappi 15-16 mm. 2n = 22, 23, 24.

Flowering spring-summer (Apr-Jul). Roadsides, pastures, fields, shrub-tree savannas; 0-1000 m; Ark., La., Mo., N.Mex., Okla., Tex.; Mexico (Coahuila, Durango, Nuevo León, San Luis Potosí, Tamaulipas).

Cirsium texanum ranges from the Chihuahuan Desert regions of trans-Pecos Texas and adjacent southeastern New Mexico across the plains of Texas and southern Oklahoma to southwestern Arkansas and southwestern Louisiana and south into north-central Mexico. D. S. Correll and M. C. Johnston (1970) suggested hybridization between Cirsium texanum and C. undulatum to explain anomalous specimens in the Edwards Plateau and trans-Pecos regions of western Texas.