Plants 5–100 cm (self-incom-patible); glandular, strongly lemon- or acrid-scented. Stems not purple-streaked. Leaf blades oblanceolate or lanceolate to linear, 6–110 mm, margins (basal leaves) 1–2-pinnatifid. Involucres ± hemispheric, 5–12 × 2–12+ mm. Phyllaries 4–14, apices shorter or longer than folded bases. Paleae in 1 series between ray and disc florets. Ray florets 3–14; laminae yellow or white, 3–26 mm. Disc florets 7–120+; corollas 3–6 mm; anthers yellow to brownish. Ray cypselae glabrous. Disc pappi 0 or of 1–22 whitish, ± equal, setiform scales 1.5–3.5 mm, each proximally plumose, seldom adaxially woolly.

Subspecies 2 (2 in the flora): California.

Molecular phylogenetic data have indicated that Layia pentachaeta is closely related to L. glandulosa and L. discoidea (B. G. Baldwin, unpubl.). Distributions of L. pentachaeta and L. glandulosa overlap broadly; the two species occur in different habitats and natural hybridization has been rarely detected (first-generation hybrids are of low to moderate fertility; J. Clausen 1951).