Bastard cabbage is an annual, many-branched, herbaceous plant that grows from 1 to 5 feet or more in height. It has a robust taproot that can become quite large and deep-rooted. Leaves are deep green, lobed and wrinkled, and sometimes have a reddish cast. The terminal lobe is larger than the lateral lobes, especially on the basal leaves. Younger leaves growing higher up on the plant are less lobed and more elongated. Bastard cabbage typically flowers from early spring into summer, bearing clusters of small, showy yellow flowers at the tips of its branches, resembling those of broccoli and cabbage. Bastard cabbage can be identified more easily and certainly by its unusually shaped fruit - a two-segmented seed capsule, called a silique. The seed capsule is stalked, with a long beak at the tip, and contains 1-2 seeds. The seeds are oval-shaped, dark brown, smooth, and tiny (about 1/16-inch).
Two subspecies of this plant are recognized: R. rugosum ssp. rugosum and R. rugosum ssp. orientale. Bastard cabbage is also known as turnip-weed, common giant mustard, ball mustard, wild turnip, wild rape and tall mustard-weed. It is designated a terrestrial noxious-weed seed in the state of Texas.
(L) Rosette. Note large terminal lobe. (R) Several plants.
(L) Flowers. (R) Fruit. Note beak at tip.