Riddellia tagetina Nuttall, Trans. Amer. Philos. Soc., n. s. 7: 371. 1841 (as tagetinae); Psilostrophe tagetina var. grandiflora (Rydberg) Heiser; P. tagetina var. lanata A. Nelson

Biennials or perennials (rarely flowering first year), 10–30(–60+) cm. Stems arachno-villous (gray to gray-green). Heads in ± loose to crowded, corymbiform arrays. Peduncles (3–)12–20(–40) mm. Involucres 4–8 mm. Rays 3–4(–6); laminae (3–)7–14+ mm, spreading in fruit. Disc florets 6–9(–12). Cypselae usually glabrous, sometimes hirtellous and/or gland-dotted; pappi of (4–)6–8 elliptic or lanceolate to lance-subulate scales 2–3+ mm. 2n = 32.

Flowering (Apr–)May–Sep(–Dec). Desert scrub, grasslands, limestone soils, saline flats, sandy soils; (300–)600–2400 m; Ariz., N.Mex., Tex., Utah; Mexico (Chihuahua, Coahuila).

See comments under 6. Psilostrophe villosa.