Perennials; (caudex simple or branched, covered with persistent petiolar remains); sparsely to moderately pubescent, trichomes sub-setiform, bulbous-based, simple, (to 1.5 mm), often mixed with fewer, forked, stalked ones. Stems simple or few from base (caudex), erect, unbranched, (0.6–)1.5–3.5(–4.5) dm, (sparsely to densely hirsute basally or throughout). Basal leaves: petiole 0.3–1.5 cm, (ciliate); blade oblanceolate to obovate, (0.5–)1–3(–4) cm × (2–)3–6(–10) mm, margins entire, repand, or obtusely dentate, (ciliate), apex obtuse, surfaces pubescent, trichomes usually simple, sometimes mixed with fewer forked ones, rarely subglabrate. Cauline leaves 3–6 (or 7); blade oblong, 0.4–1(–1.5) cm × (1–)2–4 mm, base not auriculate, margins entire or repand, apex obtuse. Racemes simple, (dense). Fruiting pedicels ascending to suberect, 8–12(–15) mm, (subglabrate or sparsely pubescent). Flowers: sepals (purple), oblong, 4–8 × 1.5–2.5 mm, lateral pair saccate basally; petals purple, spatulate, (9–)10–18(–20) × (2.5–)3.5–6(–8) mm, apex obtuse; filaments 4–9 mm; anthers oblong, 1.5–2 mm. Fruits ascending to suberect, not torulose, sometimes slightly curved, 3.5–6.5 cm × 1.5–2 mm; valves each with prominent midvein extending full length; ovules 24–36 per ovary; style (0.7–)1–2 mm. Seeds narrowly winged nearly throughout except wider distally, oblong, 1.5–2.3 × 1–1.3 mm; wing 0.1–0.3 mm wide. 2n = 32.
Phenology: Flowering Mar–May(-Jun).
Habitat: Serpentine slopes, rocky hillsides
Elevation: 200-1800 m
Arabis aculeolata is known only from Curry, Douglas, and Josephine counties.