Brassica arvensis (Linnaeus) Rabenhorst; B. kaber (de Candolle) L. C. Wheeler; B. sinapistrum Boissier; B. xinjiangensis Y. C. Lan & T. Y. Cheo; Sinapis kaber de Candolle.

Herbs (5-)20-100(-210) cm, retrorsely or spreading hirsute or hispid, rarely glabrous. Stems erect, often branched above. Petiole of basal and lower cauline leaves 1-4(-7) cm; leaf blade oblong, ovate, or lanceolate in outline, lyrate, pinnatifid, or undivided and dentate, (3-)4-18(-25) × 1.5-5(-7) cm; terminal lobe broadly ovate, obovate, to elliptic, margin dentate; lateral lobes 1-4 on each side of midvein, oblong, ovate, or lanceolate, smaller than terminal one, margin dentate. Upper cauline leaves shortly petiolate; leaf blade ovate or lanceolate, often undivided, margin dentate or subentire, apex acute. Fruiting pedicels ascending or suberect, stout, (2-)3-7(-15) mm. Sepals yellow or green, narrowly oblong, (4.5-)5-6(-7) × 1-1.8 mm, spreading or reflexed. Petals bright or pale yellow, obovate, (0.8-)0.9-1.2(-1.7) cm × (3-)4-6(-7.5) mm. Filaments (3-)4-6 mm; anthers oblong, 1.2-1.5 mm. Fruit linear, (1.5-)2-4.5(-5.7) cm × (1.5-)2.5-3.5(-4) mm; valvular segment (0.6-)1.2-3.5(-4.3) cm, (2-)4-8(-12)-seeded in each locule, 3-5(-7)-veined, torulose, terete, glabrous or pubescent with 1 kind of trichome; terminal segment conical or subulate, terete, (0.7-)1-1.6 cm, straight or curved upward, seedless or 1- or 2-seeded. Seeds blackish to dark brown, globose, (1-)1.5-2 mm in diam., finely reticulate. Fl. and fr. May-Sep. 2n = 18*.

Roadsides, waste places, fields, pastures; 400-1800 m. Xinjiang [Afghanistan, Kazakhstan, Kyrgyzstan, Mongolia, Pakistan, Russia, Tajikistan, Turkmenistan, Uzbekistan; N Africa, SW Asia, Europe; naturalized elsewhere].