Trans. Amer. Philos. Soc., n. s. 7: 315. 1840.
Annuals, biennials, or short-lived perennials, 10–250 cm (atypical, spring-blooming, dwarf dune plants have short stems; perennating from proximal stem nodes in south; aromatic); taprooted. Stems 1–5+, ascending to erect (strict, 0.9–1.7 cm diam., only distal lateral branches developing in larger plants), moderately to densely hispido-strigose, more so proximally, moderately to densely stipitate-glandular, more so distally. Leaves: basal and proximal cauline petiolate (petioles 3–7 cm, bases auriculate-clasping), blades ovate or elliptic to oblong, 50–80 × 20–30 mm, margins flat or somewhat undulate, coarsely serrate to serrulate or entire, proximally long-ciliate, apices acute, faces moderately to densely long-hispido-strigose; distal sessile, blades oblong-lanceolate to lanceolate, 20–40 × 20–30 mm, reduced distally, margins often undulate, coarsely serrate. Heads 10–110+, in corymbiform arrays, becoming paniculiform with age, branches ascending, usually relatively short compared to plant height. Peduncles 10–65 mm, sparsely to densely hispido-strigose, densely stipitate-glandular; bracts 0–3, linear-lanceolate to linear, reduced distally. Involucres campanulo-hemispheric, 6–9 mm. Phyllaries in 4–6 series, linear-lanceolate, unequal, margins scarious, faces strigose, densely stipitate-glandular. Ray florets 20–40; laminae 5–8 × 1–2 mm. Disc florets 30–75; corollas 4–6 mm, lobes 0.5–0.8 mm. Cypselae dimorphic, (ray) 2–5 mm, faces glabrous or slightly strigose on angles, (disc) 4–6 mm, faces moderately to densely strigose; pappi 0 (ray) or (disc) stramineous to rusty brown, outer bristles 0.4–0.7 mm, inner 6–9 mm, longest weakly clavate. 2n = 18.
Phenology: Flowering Apr–Dec(–Jan).
Habitat: Sandy and gravelly soils, dunes, disturbed ground, roadsides, vacant lots, fields
Elevation: 0–100(–900) m
Ariz., Calif., Nev., Utah, introduced in Pacific Islands (Hawaii).
Heterotheca grandiflora is common in California, rare and probably introduced in Arizona, Nevada, and Utah, and introduced in Hawaii. Rosette plants can bloom in the spring.