Amsonia glaberrima Woodson

Stems erect (somewhat ascending at base), (34–)48–92(–107) cm, glabrous or seldom sparsely pubescent; branches borne on distal portion of stem, exceeding infructescence. Leaves: petiole (1–)2–5(–6) mm, glabrous or slightly to moderately pubes­cent; blades not heteromorphic; stem leaf blades elliptic, narrowly oblong, lanceolate, or obovate, (3.1–)3.9–8.4(–9.3) cm × (4–)8–18(–23) mm, margins entire, often slightly revolute, usually irregularly and sometimes appearing dentate, sometimes sparsely ciliate, or moder­ately scabrous, apex acuminate, sometimes acute, sur­faces glabrous or slightly to moderately pubescent on midrib or on veins; branch leaf blades similar to stem leaf blades. Flowers: sepals narrowly deltate to deltate, (0.8–)1–1.5(–1.8) mm; corolla tube blue, greenish above, (5.5–)6–8(–8.5) mm, lobes blue (to white or rarely lavender), (4–)5–7.5 mm, outer surface of corolla glabrous (very sparsely short-pubescent). Follicles erect (sometimes partly spreading), 9–13(–15) cm × 3–4 mm, apex acute, sometimes elongated, glabrous. Seeds 8.5–12(–15) × 1.9–2.6(–3) mm.

Flowering spring; fruiting early summer to summer. Pond and swamp edges, stream bottoms and flats, stream banks, coastal prairie, wet meadows, bogs, ditches and flooded areas, moist woods, black prairie, roadsides; 10–200 m; Ala., Fla., Ga., La., Miss., Mo., Tex.

Amsonia rigida is very similar to narrow-leaved forms of the more common and widespread A. tabernaemontana, but it can be distinguished by its usually glabrous corolla and leaves with often irreg­ularly revolute margins. Almost all populations from Alabama and Mississippi, primarily from the Black Belt Prairie region, have leaf margins that are ciliate, often with short, sturdy, curved hairs, and often pale flowers. These populations have been informally labeled as a variety or species, but no name has been validly pub­lished. Although they are not formally recognized as a variety here, for conservation purposes they should be considered possibly distinct.