Layia discoidea is regarded as a strict serpentine endemic with several populations known (as of 2017) to occur on greywacke and chert outcrop and talus at the edge of the New Idria Serpentine Mass near Condon Peak, Sampson Peak, and Idria Reservoir.

The flower head is a cluster of many deep yellow disc florets with a base of bractlike scales.

Individuals of Layia discoidea occasionally display ray florets that are light yellow in color (see Calphotos and [4]).

Individuals bearing ray florets have been observed in populations at the New Idria, Laguna Mountain, and Panther Peak serpentine masses.

It is unclear if the ray florets are a result of hybridization with nearby Layia glandulosa, a genetic mutation, or simply induced by environmental conditions.