Sida 16: 6. 1994.
Perennials, 30–150 cm (polycarpic, with sparingly branched, woody caudices). Stems 1–3, usually purple-red-tinted proximally, branched distally, glabrous or ± hairy. Leaves: blades simple or lobed (lobes 3–19+), glabrous or sparsely hairy, glanddotted; mid leaves lobed (lobes 3–19+, terminal lobes 0.7–1.3 mm wide). Heads 25–400+ per plant, in paniculiform to corymbiform arrays. Peduncles 0.4–2 cm, glabrous or ± hairy. Involucres campanulate to narrowly campanulate, 5–7.5 × 2.2–4.5 mm. Phyllaries in 2 series, unequal; outer 3–5, basally connate 1/2–3/4 their lengths, obovate to oblanceolate, 4–6 mm, apices acuminate, acute, obtuse, or rounded; inner 3–5, obovate to oblanceolate, 2.5–4.5 mm, apices acuminate, acute, obtuse, or rounded, sometimes mucronate. Ray-florets 3–5; corollas yellow, extending beyond phyllaries, 3.4–6 × 1.7–4 mm. Disc-florets 6–15 (functionally staminate); corollas 3–4 mm. Cypselae obconic, 1.7–3.5 mm (hairy, hairs straight or wavy); pappi 0, or of 2–6 ± lanceolate scales 1–2.5 mm.
Varieties 3 (3 in the flora).
|1||Apices of inner phyllaries acuminate to mucronate; pappus scales 3–6 (sometimes 0 on disc florets); hairs on cypselae usually straight, sometimes slightly wavy; Arizona, Mescal, Pinaleno, and Santa Teresa mountains||Hymenoxys ambigens var. ambigens|
|1||Apices of inner phyllaries rounded or obtuse to weakly acute or mucronate; pappus scales 0 or 2–4; hairs on cypselae moderately to strongly wavy; Arizona or New Mexico||> 2|
|2||Plants 30–150 cm; outer phyllaries 3–4; hairs on cypselae strongly wavy; Arizona, Chiricahua, Dos Cabezas, Dragoon, Little Dragoon, and Mule Mountains||Hymenoxys ambigens var. floribunda|
|2||Plants 30–40+ cm; outer phyllaries 5; hairs on cypselae moderately wavy; New Mexico, Animas and Peloncillo mountains||Hymenoxys ambigens var. neomexicana|