Mexican Woollywhite

Perennials, 20–90 cm. Leaves: basal simple or 1-pinnate, 6–20 cm, lobes 5–15+ × 1–9 mm; cauline 0 or 3–6. Heads 1–8(–20+) per stem. Peduncles 1–10 cm. Phyl-laries yellowish to whitish or red-tinged, 6–9 × 2–3 mm. Ray florets 0. Disc florets 20–40; corollas yellow, 3–4.5 mm, tubes 2–2.5 mm, throats campanulate, 1–1.5 mm, lengths 3–4 times lobes. Cypselae 4–6 mm, glabrous or sparsely hirtellous; pappi of 12–20 scales 0.1–0.4 mm. 2n = 34.

Hymenopappus mexicanus A. Gray, Proc. Am. Acad. 19: 29
1883. Hymenopappus obtusifolius A. Heller, Bull. Torrey Club 26: 251. 1899.
A perennial with cespitose caudex; stems 3-6 dm. high, tomentose-floccose; leaves mostly basal, the earlier ones entire, linear-oblanceolate, 5-10 cm. long, somewhat floccose above, white-tomentose beneath, the rest of the lower leaves pinnatifid with linear-lanceolate or oblong, acute or obtuse divisions ; stem-leaves reduced, either entire or with 2-4 approximate lobes below, sessile; heads few, corymbose; involucre hemispheric, about 6 mm. high and fully 1 cm. broad; bracts broadly obovate, tomentose below, with conspicuous yellow tips; corolla lightyellow; tube and campanulate throat each 1.5 mm. long; lobes ovate, shorter than the throat; anthers partly exserted; achenes 4 mm. long, faintly striate on the faces, hispidulous or in age glabrate; pappus a mere minute crown or wanting.
Type locality: San Luis Potosi, Mexico.
Distribution: New Mexico and Arizona to San Luis Potosi.

Hymenopappus mexicanus, the Mexican woollywhite, is a North American species of flowering plant in the daisy family. It grows in northern Mexico (Chihuahua, San Luis Potosí) and the southwestern United States (Arizona, New Mexico).

Hymenopappus mexicanus is a biennial herb up to 90 cm (3 feet) tall. One plant produces 1-20 flower heads per stem, each head with 20-40 yellow disc flowers but no ray flowers.