Proc. Amer. Acad. Arts 20: 292. 1885.
Leaves: petiole 12–35 mm, often distally winged, wings often lobed, base attenuate to rounded; in lobed blades, lobes oblong-rounded to broadly falcate-acute or almost triangular, base broadly sessile along axes, margins near bases often overlapping, surfaces: abaxial tomentose, tardily glabrescent, adaxial tomentulose, soon glabrescent. Flowers: sepals 1.5–2 mm; stamens 2 mm, filaments unequal. 2n = 54.
Phenology: Flowering May–Jul.
Habitat: Canyons, ravines, ridges, and slopes in chaparral, oak woodlands, openings
Elevation: (20–)100–500+ m
Of conservation concern.
On Santa Catalina Island, most plants of Lyonothamnus floribundus have most leaves not divided into leaflets and have been called forma, subsp., or var. floribundus. Plants with most leaves palmately or pinnately divided, usually with 3–5(–7), pinnately lobed leaflets, have been called forma, subsp., or var. aspleniifolius; such plants are known from San Clemente, Santa Catalina, Santa Cruz, and Santa Rosa islands. Continuity of variation in leaf form in L. floribundus has been documented by T. S. Brandegee (1890) and others. J. M. Bushakra et al. (1999) noted genetic similarity among clones.