Description from Flora of China
Brassica alba (Linnaeus) Rabenhorst; B. hirta Moench.
Herbs (15-)25-100(-220) cm, retrorsely hispid, rarely glabrescent. Stems erect, often branched above. Petiole of basal and lower cauline leaves 1-3(-6) cm; leaf blade oblong, ovate, or lanceolate in outline, lyrate, pinnatifid, pinnatisect, (3.5-)5-14(-16) × 2-6(-8) cm; terminal lobe broadly ovate, (1-)3-6 cm, usually 3-lobed, margin dentate; lateral lobes 1-3 on each side of midvein, oblong, ovate, or lanceolate, 1.5-2.5 cm, margin dentate, repand, or rarely pinnatifid. Upper cauline leaves shortly petiolate; leaf blade ovate or oblong-ovate, 2-4.5 cm, margin coarsely dentate, rarely subentire. Fruiting pedicels divaricate, stout, (3-)6-12(-17) mm. Sepals yellow or green, narrowly oblong, (3.8-)4-7(-8) × 1-1.8 mm, spreading or reflexed. Petals pale yellow, obovate, (0.7-)0.8-1.2(-1.4) cm × (3-)4-6(-7) mm. Filaments (3-)4-7(-8) mm; anthers oblong, 1.2-1.5 mm. Fruit lanceolate, (1.5-)2-4.2(-5) cm × (2-)3-5.5(-6.5) mm; valvular segment (0.5-)0.7-1.7(-2) cm, 2-5-seeded in each locule, 3-5(-7)-veined, torulose, terete or slightly compressed, hispid with subsetose trichomes mixed with much shorter and more slender ones; terminal segment ensiform, strongly compressed, (1-)1.5-2.5(-3) cm, straight or curved upward, seedless or 1(or 2)-seeded. Seeds gray, pale brown, or reddish brown, globose, (1.7-)2-3(-3.5) mm in diam., finely reticulate. Fl. and fr. May-Sep. 2n = 24*.
The seeds are used for the manufacture of table mustard and also for the extraction of oils, which are used for cooking and making soap and mayonnaise. The species is a cosmopolitan, naturalized weed.
Roadsides, fields, pastures, disturbed sites. Anhui, Gansu, Hebei, Liaoning, Qinghai, Shandong, Shanxi, Sichuan, Xinjiang [India, Kashmir, Russia, Tajikistan, Turkmenistan, Vietnam; N Africa, SW Asia, Europe; naturalized elsewhere].