Brassica nigra, Koch. (Sinapis nigra, L.)
Time of bloom: June to September.
Seed-time: July to November.
Range: In most parts of the American Continent except the far
North; most abundant on the Pacific Coast. Habitat: Fields and waste places.
Mustard seeds, both the Black and the White, are used in making a popular condiment, also in medicine, and to express a fine, clear oil which has little or none of the sharp flavor of Mustard. The United States imports these seeds to the amount of over five million pounds annually, at a cost of three to six cents a pound.
Fig. 130. - White Mustard (Brassica alba). X 1/4.
Fig. 131. - Black Mustard (Brassica nigra).
Stems two to seven feet tall, or even more in warm southern soil, branching widely, sometimes hairy near the base but usually smooth above. Lower leaves pinnatifid, with the terminal lobe very large and the several lateral lobes small, toothed all around, with a long, slim petiole; upper leaves less divided, becoming lance-shaped and nearly sessile at the top. Flowers bright yellow, a little more than a quarter-inch broad. This plant is often confused with Charlock, or Wild Mustard, but the difference between the fruits readily distinguishes them: Charlock has long, knotted or wavy pods, with stout, two-edged beaks, while Black Mustard has short, smooth, four-angled pods, a half-inch to an inch long, with short, slim beaks; and they are held closely pressed to the stalk, making the raceme very slender. Seeds globular, almost black, very pungent to the taste. (Fig. 131.) Means of control the same as for Charlock.