Alyssum murale

Perennials; (cespitose, sometimes caudex woody); canescent or not, trichomes stellate, 5-20- rayed. Stems often several from caudex (sterile shoots absent or few), usually erect or ascending, (2.5-)3-6(-7) dm. Cauline leaves subsessile; blade narrowly oblanceolate to linear, (0.5-) 0.7-2.5(-3) cm × 1-5(-8) mm (gradually smaller distally), base cuneate to attenuate, apex obtuse to subacute, (surfaces often more grayish abaxially than adaxially). ( Racemes corymbose, in panicles terminating each stem.) Fruiting pedicels divaricate-ascending, straight or slightly curved distally, slender, (2-)2.5-6(-8) mm, trichomes uniformly stellate. Flowers: sepals oblong, 1.2-2 × 0.4-0.7 mm, stellate-pubescent; petals yellow, spatulate, 2.5-3.5 × 0.5-1 mm, base attenuate, apex often obtuse or rounded, glabrous abaxially; filaments: median pairs broadly winged, apically 1-toothed, lateral pair with lanceolate or narrowly oblong basal appendage, apically subacute, 1.5-2.5 mm; anthers oblong, 0.2-0.3 mm. Fruits broadly elliptic to orbicular, 3.5-5 × 2.5-5 mm, apex obtuse to rounded; valves not inflated, flattened and slightly undulate, stellate-pubescent; ovules 1 per ovary; style (slender) 1-2 mm, sparsely pubescent. Seeds suborbicular to broadly ovoid, compressed, 3-3.8 × 2-3.2 mm, margins winged, wing 0.5-0.9 mm wide. 2n = 16, 32.

Flowering May-Jul. Waste areas, roadsides; 1500-1800 m; introduced; Alta., B.C., Ont., Que.; Colo., Oreg., Utah; Europe; sw Asia.