Authors: Torr.
Annual or perennial, up to 30cm tall, sometimes with a simple stem but often also having decumbent basal branches, the surface of which is whitish with an exfoliating skin. Leaves at the base largest and loosely rosetted at first, obovate to lanceolate, often somewhat rhombic in outline, 2-8cm long; stem leaves progressively smaller. Flowers up to 4cm across, opening in the evening, white ageing pink, late spring (if autumn sown) or summer to autumn. California and adjacent Mexico, in desert areas under 1200m. Variable in flower size and perenniality. O.d, var. eurekensis and O.d. var. howellii are always perennial, the latter with pinnatifid leaves under 3cm long. Probably not very winter hardy.
