Arabis lemmonii S. Watson var. paddoensis Rollins, Rhodora 43: 384. 1941

Perennials; long-lived; (ces-pitose); apomictic; caudex usually woody. Stems 1-3 per caudex branch, arising from center of rosette near ground surface, or arising laterally proximal to sterile shoots, 1-2.5 dm, glabrous throughout. Basal leaves: blade narrowly oblanceolate, 1-3(-6) mm wide, margins usually entire, rarely apically few-toothed, not ciliate, surfaces sparsely pubescent, trichomes short-stalked, 4-8-rayed, 0.08-0.2 mm. Cauline leaves: 4-8, not concealing stem; blade auricles 1-2 mm, surfaces of distalmost leaves glabrous. Racemes 5-12(-18) -flowered, usually unbranched. Fruiting pedicels usually divaricate-ascending, rarely horizontal, straight, 2-5 (-10) mm, glabrous. Flowers ascending at anthesis; sepals glabrous; petals lavender to purple, 4-5.5 × 1-1.5 mm, glabrous; pollen spheroid. Fruits usually divaricate-ascending, rarely horizontal, not appressed to rachis, secund (often weakly so), straight, edges parallel, 3-5.5 cm × 1.5-2 mm; valves glabrous; ovules 42-54 per ovary; style 0.05-0.1 mm. Seeds uniseriate, 1.1-1.5 × 0.9-1.3 mm; wing continuous, 0.1-0.3 mm wide.

Flowering Jul-Aug. Rocky ridges; 1500-2100 m; Oreg., Wash.

Morphological evidence suggests that Boechera paddoensis is an apomictic species that arose through hybridization between B. lemmonii and B. lyallii (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). Boechera paddoensis is known only from the mountains of central Washington and northeastern Oregon.