[mass noun]a yellow-flowered European plant of the cabbage family. It was formerly widely grown in Britain as a source of blue dye, which was extracted from the leaves after they had been dried, powdered, and fermented 菘蓝属植物,欧洲菘蓝
Isatis tinctoria, family Cruciferae 拉丁名Isatis tinctoria,十字花科 ■the dye obtained from this plant, now superseded by synthetic products 靛蓝
语源
Old English wād, of Germanic origin; related to Dutch wede and German Waid