The greyish green leaves of physaria purpurea
are somewhat variable; their shape ranges from obovate to oblong, and the length may be more than twice the width, or broadly the same. Edges can be entire, lined by a few shallow teeth or partly pinnately lobed. Leaves grow mostly around the base but also along the stems, where they are smaller, and untoothed. Plants produce several unbranded stems, purplish at the base, green higher up. Stems and leaves have a covering of short, rough, branched hairs.
The terminal flower clusters can be compact and spherical, or slightly elongated. Flowers have four green, elliptic sepals and four larger white petals, crossed by faint lengthwise veins. The bases of the petals are green, and all the petals become dark purple as they wither. Petal shape varies from obovate to round. Fruits form at the end of short, curving stalks, pendent or spreading; they are green (sometimes tinged with purple), spherical and hairless, with a darker line separating the two valves.