Elongated mustard is a biennial, short-lived perennial, or sometimes winter annual herb with erect, branched stems up to 3 ft tall. The leaves on elongated mustard help distinguish the species from other mustards. Basal leaves are slightly lobed to shallowly toothed and lance-shaped. Upper leaves are much smaller and do not clasp the stem. The small yellow flowers have four petals and six stamens and are present from June through July. The plant has a sweet fragrance when in bloom. Fruits are 0.4 to 0.6 in long with a stalk-like base and a seedless, narrow tip.