Like many coastal plants, castilleja mendocinensis
has thick, fleshy leaves; these are green to purplish in color, rounded in shape, and covered by long white hairs, non-glandular; bracts and stems are similarly hairy. Leaves are usually unlobed. Stems grow upright or at an angle, and branch readily.
The inflorescence is relatively compact, extending between 2 and 7 inches at the top of the stem. The red to orange/red bracts are a little less than one inch long, generally obovate in shape, sometimes with two small side lobes. The red calyces are about one inch long, divided on both sides by half their length, while the tubular, greenish-yellow corollas are around twice as long.
This a rare plant, and as its species name suggests, is mostly restricted to the coast of Mendocino County, north California.