1.
Sisymbrium altissimum
Linnaeus, Sp. Pl. 2: 659. 1753.
Tumbleweed
Annuals;
glabrous or pubescent.
Stems
erect, branched distally, (2-)4-12(-16) dm, sparsely to densely hirsute basally, glabrous or glabrate distally.
Basal leaves
rosulate; petiole 1-10(-15) cm; blade broadly oblanceolate, oblong, or lanceolate (in outline), (2-)5-20(-35) cm × (10-)20-80(-100) mm, margins pinnatisect, pinnatifid, or runcinate; lobes (3-)4-6(-8) on each side, oblong or lanceolate, smaller than terminal lobe, margins entire, dentate, or lobed.
Cauline leaves
similar to basal; distalmost blade with linear to filiform lobes.
Fruiting pedicels
usually divaricate, rarely ascending, stout, nearly as wide as fruit, (4-)6-10(-13) mm.
Flowers:
sepals ascending or spreading, oblong, (cucullate), 4-6 × 1-2 mm; petals spatulate, (5-)6-8(-10) × 2.5-4 mm, claw 3.5-6 mm; filaments 2-6 mm; anthers oblong, 1.5-2.2 mm.
Fruits
narrowly linear, usually straight, smooth, stout, (4.5-)6-9(-12) cm × 1-2 mm; valves glabrous; ovules 90-120 per ovary; style 0.5-2 mm; stigma prominently 2-lobed.
Seeds
0.8-1 × 0.5-0.6 mm.
2
n
= 14.
Flowering Apr-Sep. Roadsides, fields, pastures, waste grounds, disturbed sites, grasslands; 0-2700 m; introduced; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Conn., D.C., Fla., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; w Asia; nw Africa; introduced also in South America (Argentina, Chile).
