Annuals, biennials, or, rarely, perennials; not scapose; glabrous, glabrescent, or pubescent. Stems erect, unbranched or branched distally. Leaves basal and cauline; petiolate or sessile; basal (persistent in B. tournefortii), rosulate or not, petiolate, blade margins entire, dentate, or lyrate-pinnatifid; cauline petiolate or sessile, blade (base sometimes auriculate or amplexicaul), margins entire, dentate, lobed, or sinuate-serrate. Racemes (corymbose), considerably elongated in fruit. Fruiting pedicels erect, spreading, ascending or divaricately-ascending, often slender. Flowers: sepals usually erect or ascending, rarely spreading, oblong [ovate], lateral pair usually saccate basally; petals yellow to orange-yellow [rarely white], obovate, ovate, elliptic, or oblanceolate, claw often differentiated from blade, (sometimes attenuate basally, apex rounded or emarginate); stamens tetradynamous; filaments slender; anthers oblong or ovate, (apex obtuse); nectar glands confluent or not, median glands present. Fruits siliques, dehiscent, sessile or stipitate, segments 2, linear, torulose or smooth, terete, 4-angled, or latiseptate; (terminal segment seedless or 1–3-seeded, usually filiform or conic, rarely cylindrical); valves each prominently 1-veined, glabrous; replum rounded; septum complete; ovules [4–]10–50 per ovary; stigma entire or 2-lobed. Seeds uniseriate, plump, not winged, globose; seed coat (reticulate or reticulate-alveolate), mucilaginous or not when wetted; cotyledons conduplicate. x = 7, 8, 9, 10, 11.
Introduced; sw Europe, sw Asia, e, nw Africa, introduced also in Mexico, West Indies, Central America, South America, Atlantic Islands, Pacific Islands (New Zealand), Australia.
Species 35 (8 in the flora).
Crops of Brassica are the most important economic plants of the family. Probably, the earliest known utilization of mustards dates from Sanskrit records in India to 3000 b.c., but there is archaeological evidence suggesting that cultivation of cabbage in coastal northern Europe was occurring nearly 8000 years ago. Brassica crops include oilseeds, food crops (e.g., B. juncea, Asian vegetables; B. oleracea, cole crops; B. rapa, Chinese cabbages), fodder for animals, and condiments (B. juncea or B. nigra). The latter two species have also been used for medicinal purposes (I. A. Al-Shehbaz 1985). In addition to being noxious weeds, some species of Brassica are harmful or poisonous to humans and livestock (Al-Shehbaz).
Historically, native peoples of North America have used a number of “wild” Brassica species for both food and medicinal purposes (T. Arnason et al. 1981; H. A. Jacobson et al. 1988): Brassica species—young shoots cooked as greens by Iroquois and Malecite Indian tribes; B. nigra—seeds ground and used as snuff to cure head colds by the Meskwaki, and leaves used to relieve toothaches and headaches by the Mohegans; B. napus—bark used to treat colds, cough, grippe, and smallpox by the Micmac, and used for chilblains by the Rappahannock; B. oleracea—used for headaches by the Rappahannock; and B. rapa—used as medicine by the Bois Fort Chippewa.
|1||Cauline leaves sessile, blade bases auriculate and/or amplexicaul||> 2|
|1||Cauline leaves petiolate or sessile, blade bases tapered, not auriculate or amplexicaul||> 4|
|2||Biennials or perennials; petals (15-)18-25(-30) mm; terminal segments of fruits (3-)4-11 mm.||Brassica oleracea|
|2||Annuals or biennials; petals 6-16 mm; terminal segments of fruits (5-)8-22 mm||> 3|
|3||Flowers usually not overtopping buds, rarely at same level, when open; petals pale yellow, 10-16 mm; terminal segments of fruits (5-)9-16 mm.||Brassica napus|
|3||Flowers overtopping or equaling buds when open; petals deep yellow, 6-11(-13) mm; terminal segments of fruits 8-22 mm.||Brassica rapa|
|4||Fruits and pedicels erect, ± appressed to rachises; fruits 10-25(-27) mm, not torulose; fruiting pedicels (2-)3-5(-6) mm.||Brassica nigra|
|4||Fruits and pedicels spreading to ascending, not appressed to rachises; fruits often 2 cm+, torulose; fruiting pedicels (6-)8-20 mm||> 5|
|5||Fruits stipitate, gynophores 1.5-4(-5) mm, terminal segments 0.5-2.5(-3) mm; basal leaf blade margins entire or dentate.||Brassica elongata|
|5||Fruits sessile or stipitate, gynophores to 1 mm, terminal segments (4-)5-20 mm; basal leaf blade margins lyrate to pinnatisect, or pinnatifid to pinnately lobed||> 6|
|6||Basal leaves persistent, blades with 4-10 lobes each side, surfaces hirsute; petals 4-7 × 1.5-2(-2.5) mm.||Brassica tournefortii|
|6||Basal leaves deciduous, blades with 1-3 (or 4) lobes each side, surfaces glabrous or nearly so; petals (7-)9-13 × 3-7.5 mm||> 7|
|7||Fruits stipitate (gynophore 1-1.5 mm), 1.5-3 cm × 1.5-2 mm, terminal segment 3-6 mm.||Brassica fruticulosa|
|7||Fruits sessile, (2-)3-5(-6) cm × 2-5 mm, terminal segment (4-)5-10 (-15) mm.||Brassica juncea|