2. Diplotaxis muralis (Linnaeus) de Candolle, Syst. Nat. 2: 634. 1821.
Annual or stinking wall-rocket, stink-weed, cross-weed, sand-rocket, wall-mustard
Sisymbrium murale Linnaeus, Sp. Pl. 2: 658. 1753; Sinapis muralis (Linnaeus) W. T. Aiton
Annuals or perennials, (short-lived, frequently scapose or subscapose, taprooted), strongly scented (with glucosinolates). Stems ascending to suberect, (0.5-)2-5(-6) dm, moderately pubescent (trichomes predominantly patent basally, retrorse distally to near racemes). Basal leaves (rosulate); blade elliptic to obovate, 2-9 cm × 10-35 mm, margins sinuate to pinnatifid, lyrate, [2-4(-6) lobes each side], (margins and veins glabrescent to sparsely pubescent). Cauline leaves shortly petiolate to sessile; blade margins entire or dentate. Fruiting pedicels (3-) 8-20(-37) mm. Flowers: sepals 3-5.5 mm, pubescent or glabrous, trichomes straight; petals yellow, 5-8(-10) × 3-5 mm; filaments 3.5-6 mm; anthers 1.5-2 mm; gynophore obsolete or to 0.5 mm. Fruits erect-patent, (1.5-)2-4 cm × 1.5-2.5 mm; terminal segment beaklike, (1-)1.5-3 mm, seedless; (ovules 20-36 per ovary). Seeds 0.9-1.3 × 0.6-0.9 mm. 2n = 42.
Flowering spring-fall. Waste ground, disturbed or cultivated soil, ballast places, wharves, roadsides, railroads, around buildings, grazed grasslands; 80-2000 m; introduced; Alta., N.B., N.S., Ont., P.E.I., Que., Sask.; Ala., Ariz., Ark., Calif., Conn., Fla., Ill., Ind., Iowa, Kans., Mass., Mich., Minn., Mont., Nebr., N.J., N.Mex., N.Y., Ohio, Oreg., Pa., Tex., Utah, Wis.; Eurasia; Africa; introduced also in Mexico (Coahuila, Nuevo León), West Indies (Bahamas), Bermuda, South America, Pacific Islands (New Zealand), Australia.
Diplotaxis muralis was introduced from Europe as a ballast plant in the last century and may have failed to persist in some of the recorded provinces and states. It is an allopolyploid arisen from D. tenuifolia and the Eurasian D. viminea (Linnaeus) de Candolle with 2n = 20 (M. D. Sánchez-Yélamo and J. B. Martínez-Laborde 1991; K. Mummenhoff et al. 1993; G. Eschmann-Grupe et al. 2003). There does not seem to be a sound basis for attributing D. viminea to the flora area, as done by V. I. Dorofeev (1998), because most specimens cited by him belong, in fact, to D. muralis.