Flowering Mar-Apr. Open, rocky or gravelly desert slopes and flats, shrublands; of conservation concern; 0-200 m; Calif.
Variety peirsonii is known from the eastern Santa Rosa Mountains and adjacent Salton Sea area near the common border of Imperial, Riverside, and San Diego counties. Unlike var. attenuata, in which it has sometimes been included, var. peirsonii is geographically and morphologically well defined.