This is an introduced annual plant about 1.5' to 3.5' tall that branches occasionally to abundantly. Initially, it forms a low rosette of basal leaves; this is followed by flowering stalks with alternate leaves. The stems are light green to purplish green, and usually glaucous; there are scattered white hairs along the lower stem(s), while the upper stems are hairless. The basal and lower alternate leaves are up to 8" long and 2" across; they are pinnatifid with several pairs of narrow lobes. The upper leaves are up to 4" long and 1½\" across; they are divided into 3 lobes (a terminal lobe and 2 lateral ones) or lanceolate-ovate in shape. The upper surfaces of these leaves are dull green and hairless; their margins are irregularly dentate or shallowly cleft. The basal and lower leaves have long petioles, while the upper leaves have short petioles or they are sessile. The upper stems terminate in long slender racemes of yellow flowers up to 10" long; axillary racemes from the upper leaves are also produced. The flowers are concentrated toward the apex of each raceme, while small siliques (narrowly cylindrical seedpods) develop below. Each flower is a little less than ¼" across; it has 4 yellow petals, 4 green to yellow sepals, a stout central style, and several stamens. The siliques are less than 2/3" long and stiffly erect or appressed against the central stalk of the raceme; each silique is a little wider at the base than at the apex. The typical variety of Hedge Mustard has pubescent siliques, while var. leiocarpum has glabrous siliques. The pedicels of the siliques are very short (about 1/8" long). The blooming period usually occurs during the summer for about 2 months; some plants may bloom during the late spring or fall. Siliques become light brown at maturity; each silique splits in half to release several seeds. The small seeds are short-cylindrical in shape, slightly flattened, reddish brown, and about 1 mm. in length. The root system consists of a taproot. This plant spreads by reseeding itself.