Proc. Amer. Acad. Arts 19: 18. 1883.
Plants 7–55 cm (self-incompatible); glandular, not strongly scented. Stems usually purple-streaked. Leaf-blades lanceolate or oblanceolate to linear, 10–70 (–90) mm, margins (basal leaves) lobed to pinnatifid. Involucres ± broadly urceolate, 4–8 × 4–8 (–12) mm. Phyllaries 13–27, apices usually shorter, sometimes longer than folded bases. Paleae in 1 series between ray and disc-florets. Ray-florets 13–27 (in 2 series); laminae proximally yellow, distally white, 5–10 (–14) mm. Disc-florets 35–100+; corollas 3–5 mm; anthers ± dark purple. Ray cypselae glabrous. Disc pappi 0 or of 8–14 whitish, ± ovate or elliptic, ± equal scales 0.5–2 mm, not plumose, not adaxially woolly (bases sparsely setose). 2n = 14.
Phenology: Flowering Mar–May.
Habitat: Grasslands, openings in chaparral, on clay or serpentine soils
Elevation: 0–400 m
Of conservation concern.
Layia jonesii occurs on the immediate coast from Cayucos to Morro Bay and in the Outer South Coast Ranges near San Luis Obispo. Layia jonesii is most closely related to L. leucopappa and L. munzii (B. G. Baldwin, unpubl.); the three species are interfertile (they do not co-occur; J. Clausen 1951).