10. Brassica L. (mustard)
Plants annual or biennial (woody-based perennials or shrubs elsewhere),
terrestrial, glabrous or with unbranched, frequently coarse, spreading hairs.
Stems erect, usually branched. Leaves alternate and basal, the lower leaves
usually relatively long-petiolate, the upper leaves progressively reduced and
short-petiolate or sessile, the bases clasping or not clasping, the leaf blades
entire to pinnately divided and toothed. Inflorescences panicles or racemes,
the lower branches rarely subtended by reduced leaves, the flowers bractless.
Sepals erect or ascending, mostly narrowly oblong or linear-lanceolate. Petals
unlobed, yellow, without conspicuously darkened veins. Fruits 10–70 mm
long, mostly more than 10 times as long as wide, spreading, ascending, or erect
(reflexed elsewhere), straight or slightly arched upward, circular or somewhat
4-angled in cross-section, short- to long-beaked with a distinct, tapering,
usually seedless area in addition to the style, the portion below the beak dehiscing
longitudinally, each valve with a midnerve. Seeds in 1 row in each locule,
1.2–1.7 mm long, globose, the surface with a fine to coarse, netlike or
honeycomb-like pattern of ridges and pits, reddish brown to gray or black.
About 40 species, Europe, Asia, Africa, a few
species introduced nearly worldwide.
The genus Brassica is of tremendous economic importance for its
agricultural crop species, with major uses ranging from vegetables to seed
oils. One species, B. oleracea L., has numerous economically important
cultivars, including broccoli, brussels sprouts, cabbage, cauliflower,
collards, kale, and kohlrabi, the so-called kohl crops that have been advocated
as potentially reducing the risk of heart disease when eaten regularly. Several
species have been used pharmaceutically and medicinally, and some of the weedy
species have been shown to be poisonous to humans and livestock when ingested
in large quantities (Al-Shehbaz, 1985).
Mühlenbach (1983) reported B. oleracea as a member of the synanthropic
railroad flora of the St. Louis
area; however, this report was based upon misdetermined specimens of B.
juncea. Brassica oleracea rarely if ever becomes established outside of
cultivation and was not accepted as naturalized in the recent treatments of
Al-Shehbaz (1985) for the southeastern United States and Rollins (1993) for