3. Sisymbrium officinale (L.) Scop. (hedge mustard)

S. officinale var. leiocarpum DC.

Pl. 328 f, g; Map 1393

Stems 25–75(–110) cm long, sparsely to usually densely hairy, especially near the base. Leaves 2–20 cm long, hairy or the uppermost leaves sometimes nearly glabrous, the middle and lowermost leaves petiolate, lanceolate to lanceolate-triangular in outline, pinnately lobed or divided into 3–11 lobes, these entire to irregularly toothed or lobed, the uppermost leaves often sessile, triangular to narrowly lanceolate in outline, entire or pinnately 3–5 lobed, the lobes entire or few-toothed. Sepals 1.0–2.0(–2.5) mm long. Petals 2.5–4.0 mm long. Style (0.8–)1.0–1.5(–2.0) mm long at fruiting. Fruits 0.7–1.8 cm long, erect, appressed to the inflorescence axis, the stalk 1.5–3.0(–4.0) mm long, relatively stout, about as wide as the fruit. Seeds 10–20 per fruit, 1.0–1.3 mm long. 2n=14. May–October.

Introduced, scattered nearly throughout Missouri (native of Europe, Asia; introduced widely in North America). Banks of streams and rivers; also fallow fields, pastures, farmyards, railroads, roadsides, and open, disturbed areas.

Sisymbrium officinale is the most widespread species of the genus in the state. Missouri plants of this species mostly have glabrous or nearly glabrous fruits. These have been referred to as var. leiocarpum. However, presence and density of pubescence varies greatly in the species, and these variants are not worthy of formal taxonomic recognition.