Lepidium serra is a small, many-branched shrub, standing 60 to 180 cm tall, notable for its pubescence with simple hairs. The leaves are simple and alternate, occasionally opposite, and tend to be crowded at the ends of the branches. These blades are typically elliptic, sometimes lanceolate or oblanceolate, measuring 6 to 17 cm in length and 0.6 to 4 cm in width, with thin, non-fleshy, glabrous surfaces. The leaf margins are serrate to the base with teeth that are acuminate to acute, and sometimes obtuse. Each leaf has a 1 to 4-cm long petiole, and there are no stipules. The plant’s flowers are generally bractless, forming in paniculate racemes with a puberulent texture. These racemes are accompanied by linear, leaf-like bracts 2 to 3 cm long. The flowers are bisexual (perfect), actinomorphic, or sometimes slightly irregular, and appear in white, pale yellow, or greenish hues, usually 2 to 3 mm long. The calyx consists of four sepals, which are deciduous, erect, and oblong, with the inner two sometimes having gibbous bases for nectar. The petals are usually four in number, yellow, white, or lavender, and range from 1 to 1.5 mm in length. There are six stamens that are longer than the petals, with dithecal anthers that open longitudinally. The superior ovary is usually 2-celled, with ovules borne on parietal placentas and a short or absent style leading to a capitate stigma. The fruit is a capsule, elongate and referred to as a silique, divided into two cells by a thin membranous septum and is depressed-orbicular in shape. It measures 2.5 to 3.1 mm long and 4 to 4.5 mm wide, with a conspicuously roughened surface. The reddish-brown seeds are suborbicular, 1.6 to 2 mm in diameter, with thin winged margins, and often become mucilaginous when wet. It is typically found on rocky ledges and cliffs within mesic forests between 450 to 1,160 meters.