Actinea herbacea (Greene) B. L. Robinson; Hymenoxys acaulis (Pursh) K. F. Parker var. glabra (A. Gray) K. F. Parker; H. herbacea (Greene) Cronquist

Perennials, 6–35+ cm. Caudices ± branched, branches notably thickened distally. Stems 1–10, erect, unbranched. Leaves all basal, new leaves tightly clustered; blades spatulate or oblanceolate to linear-oblanceolate, entire, glabrous or sparsely to rarely moderately hairy, moderately to densely gland-dotted. Heads 1–10 per plant, borne singly. Peduncles 5–35 cm, ± hairy proximally, densely hairy distally. Involucres 10–15 × 12–20 mm. Outer phyllaries 8–12, 5–7.5 mm, margins 0–0.2 mm wide, sometimes slightly scarious, abaxial faces ± hairy. Ray florets 14–27; corollas 11.8–20 mm. Disc florets 50–100+; corollas yellow, 3.4–4 mm. Cypselae 2.4–3.4 mm; pappi of 4–7 obovate, usually non-aristate scales 1.9–2.2 mm. 2n = 28.

Flowering (Apr–)May–Jun(–Oct). Alvars (limestone flats), openings in woods; 200 m; Ont.; Ill., Ohio.

Tetraneuris herbacea is in the Center for Plant Conservation’s National Collection of Endangered Plants.