Alyssum desertorum

Annuals; canescent throughout except fruit, trichomes appressed, 8-20-rayed. Stems simple or few to several from base, erect, ascending, or decumbent, (0.2-)0.5-1.8(-2.8) dm. Cauline leaves subsessile or (proximal) attenuate to petiole-like base (to 0.5 cm); blade linear to oblanceolate-linear, (0.3-)0.5-2.5(-3) cm × (0.5-)1-3(-4) mm (gradually smaller distally), base attenuate, apex acute. Fruiting pedicels ascending or subdivaricate, straight, stout, (1-)1.5-3.5(-4.5) mm, trichomes uniformly stellate. Flowers: sepals oblong, 1.4-1.8(-2) × 0.4-0.5 mm, stellate-pubescent; petals pale yellow, oblanceolate, 2-2.5 × 0.5-0.6 mm, base attenuate, apex obtuse or retuse, sparsely stellate-pubescent abaxially; filaments: median pairs not toothed, gradually expanded from apex to narrowly winged base, lateral pair with broadly winged appendage apically notched into 2 teeth, 1-1.8(-2) mm; anthers ovate, 0.1-0.2 mm. Fruits orbicular, 2.5-4(-4.5) mm diam., apex shallowly emarginate, usually glabrous; valves uniformly inflated at middle, broadly flattened at margins, often glaucous, rarely sparsely pubescent (when young); ovules 2 per ovary; style 0.3-0.7 mm, glabrous. Seeds ovoid, slightly compressed, 1.2-1.5 × 0.9-1.1 mm, margined or not. 2n = 32.

Flowering Apr-Jul. Deserts, rocky areas, disturbed sites, roadsides, fields, meadows, sagebrush flats; 800-2000 m; introduced; Alta., B.C., Sask.; Calif., Colo., Idaho, Mont., Nebr., Nev., N.Dak., Oreg., S.Dak., Utah, Wash., Wyo.; Europe; c Asia.