Perennial, 1-2 m tall, branched, robust herb, glabrous or subhairy; main stem 6-12 cm thick at the base. Basal leaves pinnatisect, 7-9-jugate, 15-30 cm long; lobes 10-20 cm long, 1-5 cm broad, oblong-lanceolate, serrate or sinuatedentate, apex ± acuminate; upper leaves gradually becoming smaller; uppermost lanceolate or linear, entire or sinuate-toothed. Racemes panicled, large, dense, many flowered, up to 20 cm long in fruit. Flowers c. 1 cm across, white or creamy yellow; pedicels up to 20 mm long in fruit. Sepals 5-5.5 mm long, 2-3 mm broad, Petals 4.5-6 mm long, 2-3 mm broad. Stamens 8-16, subequal, 4.5-5 mm long; anthers c. 1.5 mm long. Siliculae large, sub-orbicular, 3-3.5 cm long, 3.5-5 cm broad, bilobed, deeply notched at the apex and slightly at the base; lobes sometimes unequal in size, rarely one lobe abortive; wing about as broad as the locule; seed c. 1 cm in diameter, suborbicular, not winged or margined, brown.