Perennials; (caudex simple or many-branched). Trichomes of leaves 2- or 3-rayed. Stems erect, unbranched or branched (several) basally, 0.4-3 dm. Basal leaves: blade usually oblanceolate, rarely spatulate, 2-8 cm × 3-10 mm, base attenuate, margins entire or dentate, apex acute or obtuse. Cauline leaves (distal) sessile; blade margins entire or dentate-sinuate. Racemes considerably elongated in fruit. Fruiting pedicels divaricate-ascending, slender, narrower than fruit, 5-8 mm. Flowers: sepals oblong to linear-oblong, 7-10 mm, lateral pair saccate basally; petals yellow, obovate, 14-27 × 3.5-6 mm, claw 9-13 mm, apex rounded; median filaments 9-12 mm; anthers linear, 2-3.5 mm. Fruits erect to ascending, narrowly linear, often straight, sometimes twisted, strongly torulose, 3-10(-12) cm × 1.5-2.7 mm, latiseptate, not striped; valves with somewhat prominent midvein, pubescent outside, trichomes 2-4-rayed, glabrous inside; ovules 24-42 per ovary; style cylindrical, slender, 1.5-5 mm, sparsely pubescent; stigma slightly 2-lobed, lobes as long as wide. Seeds oblong, 2-3.5 × 0.8-1.5 mm; not winged or winged distally. 2n = 36. Flowering Jun-Aug. Rock crevices, talus slopes, alpine areas, open ridges, gravelly ground; 900-2200 m; B.C.; Oreg., Wash. Erysimum arenicola is distributed at the higher elevations of northern Oregon northward into the Olympic and Cascade mountains in Washington and Vancouver Island.
Both G. B. Rossbach (1958) and R. C. Rollins (1993) recognized Erysimum arenicola as a distinct species. It is closely related to E. perenne and both can be easily distinguished from E. capitatum, with which they hybridize where their ranges meet, by the strongly torulose (versus not torulose) fruits and the longer styles 1.5-5.5 versus 0.2-2.5(-3) mm.