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FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Cirsium

13. Cirsium engelmannii Rydberg, Fl. Rocky Mts. 1069. 1917.

Blackland or Engelmann’s thistle

Cirsium virginianum (Linnaeus) Michaux var. filipendulum A. Gray, Manual ed. 2, 233. 1856, not C. filipendulum Lange 1861; C. terrae-nigrae Shinners

Biennials or monocarpic perennials, 40–200 cm; taproots and clusters of coarse fibrous roots that often have tuberlike thickenings. Stems single, erect, often branched above middle, thinly arachnoid-tomentose, ± glabrate; branches few, ascending. Leaves: blades elliptic or ovate, 5–20 × 1–10 cm, usually deeply pinnatifid, lobes narrowly to broadly triangular, sinuses broad, rounded (basal and distal cauline sometimes less divided, lobes linear-lanceolate), margins revolute, spreading, entire or spinulose to remotely few-toothed or sharply lobed, main spines slender, 1–5 mm, abaxial faces white-tomentose, adaxial green, villous with septate trichomes or glabrate; basal usually absent at flowering, winged-petiolate, bases tapered; principal cauline well distributed, gradually reduced, bases narrowed, sometimes weakly clasping; distal reduced, widely separated, distalmost bractlike. Heads 1–10+, borne at tips of main stem and branches. Peduncles 2–20+ cm, essentially naked with much reduced bracts. Involucres ovoid to broadly cylindric or campanulate, 2.5–3.5 × 2–3 cm, thinly arachnoid. Phyllaries in 10–12 series, strongly imbricate, greenish with subapical darker central zone, ovate (outer) to lanceolate (inner), abaxial faces with narrow glutinous ridge; outer and middle entire, bodies appressed, spines abruptly spreading to deflexed, slender, 2–4 mm; apices of inner phyllaries narrow, flexuous, flattened, entire or finely erose. Corollas pink to purple (white), 32–38 mm, tubes 15–20 mm, throats 6–9 mm, lobes 8–11 mm; style tips 5–6 mm. Cypselae brown, 5–6 mm, apical collars yellow, ca. 1 mm; pappi 25–30 mm. 2n = 18 (as C. terrae-nigrae), 20 + 1B.

Flowering spring–summer (May–Jul). Tallgrass prairies, old fields, roadsides, oak savannas, forest edges, in calcareous clay or rarely sandy soils; 50–200 m; La., Okla., Tex.

Cirsium engelmannii occurs mostly in the blackland prairies of eastern Texas. It ranges northward into southeastern Oklahoma and eastward to northwestern Arkansas.


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