It has lobed leaves, elliptic (cup-shaped) drooping flowers with dark maroon-colored petals, and many yellow anthers.

The petals are dark red or purplish, sometimes almost black, while the margins are lighter, elliptic in shape and 1½–2½ cm long, usually longer than the sepals.

It can still be easily distinguished from P. browniii however by 35–75 cm high stems bearing seven to twelve leaves which are green, while the leaflet blade gradually eases into the leaflet stalk or lacks such a stalk all together, and the finest lobes are lanceolate or narrowly elliptic.

P. brownii is only 20–40 cm high, has six to eight glaucous leaves per stem that suddenly narrow at their base and the finest segments are egg-shaped.

[2] Paeonia californica was first described in 1838 by Thomas Nuttall in the Flora of North America which was edited by John Torrey and Asa Gray.

Several later authors considered it a subtaxon of P. brownii: a subspecies (Abrams in 1944, and Halda in 1997) or a variety (Lynch, 1890).

[4][5] all Eurasian herbaceous peonies all other tree peonies P. ludlowii P. delavayi P. brownii P. californica California peonies have a native distribution in southwestern California (Los Angeles, Monterey, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, San Luis Obispo and Ventura Counties) and in neighboring Mexico (northern Baja California), although distribution in Mexico is poorly known.