Description from Flora of China
Brassica asperifolia Lamarck; B. campestris Linnaeus; B. campestris var. chinoleifera Viehoever; B. campestris subsp. nipposinica (L. H. Bailey) G. Olsson; B. campestris (Linnaeus) subsp. oleifera (de Candolle) Schübler & Martius; B. campestris var. oleifera de Candolle; B. chinensis Linnaeus var. angustifolia V. G. Sun; B. chinensis var. utilis M. Tsen & S. H. Lee; B. dubiosa L. H. Bailey; B. nipposinica L. H. Bailey; B. perviridis (L. H. Bailey) L. H. Bailey; B. rapa subsp. campestris (Linnaeus) Clapham; B. rapa subsp. nipposinica (L. H. Bailey) Hanelt; B. rapa subsp. oleifera (de Candolle) Metzger; B. rapa var. campestris (Linnaeus) Petermann; B. rapa var. chinoleifera (Viehoever) Kitamura; B. rapa var. perviridis L. H. Bailey.
Plants annual or rarely biennial. Taproot not fleshy, cylindric. Basal leaves rarely up to 10, not rosulate or obscurely rosulate; petiole slender, neither fleshy nor winged; leaf blade subentire, sinuately lobed, pinnatifid, or incised with irregularly serrate lobes. Fl. Mar-May, fr. May-Jul. 2n = 20*.
Widely cultivated in Asia as a source of seed oil, but also grown in China as a medicinal plant and vegetable for its purple shoots. Plants of this variety are weedy throughout much of the world and are better known as Brassica campestris.
Purplish forms of this subspecies with shallowly lobed or unlobed basal leaves are cultivated in China as a vegetable. They were originally described as Brassica campestris var. purpuraria L. H. Bailey and later as B. purpuraria (L. H. Bailey) L. H. Bailey. If a formal recognition were needed, then the name would be B. rapa var. purpuraria (L. H. Bailey) Kitamura (Mem. Coll. Sci. Kyoto Imp. Univ., Ser. B, Biol. 19: 78. 1950).
Another leafy form, originally described from Sichuan and later cultivated in Jiangsu and many other provinces, is Brassica juncea var. celerifolia M. Tsen & S. H. Lee (Hort. Sin. 2: 28. 1942). It was correctly excluded from B. juncea because it has 2n = 20, but was raised to the rank of species, as B. celerifolia (M. Tsen & S. H. Lee) Y. C. Lan & T. Y. Cheo (Acta Phytotax. Sin. 29: 74. 1991). It has deeply incised leaf blades.
Cultivated. Throughout China [widely cultivated elsewhere].