Sisymbrium incanum Bernhardi ex Fischer & C. A. Meyer, Index Seminum (St. Petersburg) 1: 38. 1835; Descurainia incana var. brevipes (Nuttall) S. L. Welsh; D. incana var. macrosperma (O. E. Schulz) Dorn; D. incana var. major (Hooker) Dorn; D. incana subsp. procera (Greene) Kartesz & Gandhi; D. richardsonii var. alpestris (Cockerell) O. E. Schulz; D. richardsonii var. brevipes (Nuttall) S. L. Welsh & Reveal; D. richardsonii var. macrosperma O. E. Schulz; D. richardsonii subsp. procera (Greene) Detling; D. richardsonii var. procera (Greene) Breitung; S. canescens Nuttall var. alpestre Cockerell; S. canescens var. brevipes Nuttall; S. canescens var. major Hooker; S. procerum (Greene) K. Schumann; Sophia brevipes (Nuttall) Rydberg; S. procera Greene

Biennials; usually eglandular, rarely glandular; finely pubescent, sometimes canescent, trichomes dendritic. Stems erect, unbranched basally, often many-branched distally, (1.5-)2.5-12 dm. Basal leaves: petiole 1-3.5(-5.5) cm; blade pinnatifid, broadly lanceolate to oblanceolate or obovate in outline, 1.5-10(-13) cm, lateral lobes linear to oblong or narrowly lanceolate, [3-10(-15) × 1-3(-5) mm], margins entire. Cauline leaves sessile or shortly petiolate; blade smaller distally, distal lobes often narrower. Racemes considerably elongated in fruit. Fruiting pedicels erect to erect-ascending, straight, 2-8(-11) mm. Flowers: sepals erect, yellowish, oblong, 1-1.8 mm, sparsely pubescent; petals oblanceolate, 1.2-2 × 0.3-0.6 mm; median filaments 1.4-2 mm; anthers 0.3-0.4 mm. Fruits erect, (often strictly appressed to rachis), linear, slightly torulose, (4-)5-10(-15) × 0.7-1.2(-1.5) mm, (acute at both ends); valves each with distinct midvein; septum often with distinct midvein; ovules 14-22 per ovary; style 0.1-0.4 mm, glabrous. Seeds uniseriate, reddish brown, ellipsoid to narrowly oblong, 0.8-1.2 × 0.4-0.5 mm. 2n = 14, 28.

Flowering May-Sep. Alpine and subalpine areas, gravel and sand bars, scree, grassy slopes, prairies, steep rocky slopes, roadsides, disturbed sites, waste grounds, meadows, spruce-fir, pine, aspen, or sagebrush communities; 100-3500 m; Alta., B.C., Man., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Calif., Colo., Idaho, Maine, Minn., Mont., Nev., N.Mex., N.Dak., S.Dak., Utah, Wyo.

Descurainia incana is a distinctive species readily separated from the other North American taxa of the genus by having fruits and fruiting bases strictly appressed to rachises, and septums with a distinct midvein. Collections identified as such, but with fruits and pedicels not or only weakly appressed to the rachis, most likely represent hybrids between this species and others.