Nasturtium perfoliatum (Linnaeus) Besser

Annuals or biennials; (glaucous), glabrous or sparsely pubescent proximally. Stems simple from base, erect, branched distally, (0.7-)1.5-4.3(-5.6) dm. Basal leaves rosulate; petiole (0.5-) 1-2(-4) cm; blade 2- or 3-pinnatifid or pinnatisect (lobes linear to oblong), (1-)3-8(-15) cm, margins entire. Cauline leaves sessile; blade ovate to cordate or suborbicular, (0.5-)1-3 (-4) cm × (5-)10-25(-35) mm, base deeply cordate-amplexicaul, not auriculate, margins entire. Racemes considerably elongated in fruit; rachis glabrous. Fruiting pedicels divaricate-ascending to horizontal, straight, (terete), 3-6(-7) × 0.2-0.3 mm, glabrous. Flowers: sepals oblong, 0.8-1(-1.3) × 0.5-0.8 mm; petals pale yellow, narrowly spatulate, 1-1.5(-1.9) × 0.2-0.5 mm, claw 0.5-1 mm; stamens 6; filaments 0.6-0.9 mm, (glabrous); anthers 0.1-0.2 mm. Fruits orbicular to rhombic or broadly obovate, 3-4.5 (-5) × 3-4.1 mm, apically winged, apical notch 0.1-0.3 mm deep; valves thin, smooth, not or obscurely veined, glabrous; style 0.1-0.4 mm, subequaling or slightly exserted beyond apical notch. Seeds (dark brown), ovate, 1.6-2(-2.3) × 1.2-1.4 mm. 2n = 16.

Flowering Mar-Jun. Waste places, dry sandy slopes, pinyon-juniper woodlands, sagebrush flats, open deserts, roadsides, pastures, meadows, open grasslands, alkaline flats and sinks, fields, disturbed sites; 0-2500 m; introduced; Alta., B.C., Man., Ont., Sask.; Ariz., Ark., Calif., Colo., Conn., Ga., Idaho, Ind., Iowa, Kans., Maine, Mass., Mich., Miss., Mo., Mont., Nebr., Nev., N.Mex., N.Y., N.C., Ohio, Okla., Oreg., Pa., S.Dak., Tenn., Utah, Wash., Wis., Wyo.; Europe; Asia; n Africa; introduced also in Mexico (Baja California), South America (Argentina), Australia.