Myagrum perfoliatum Linnaeus, Sp. Pl. 2: 640. 1753. TYPE: “Habitat inter Galliae segetes,” (lectotype designated by Hedge (in Jarvis et al., Regnum Veg. 127: 68. 1993): Herb. Linn. No. 819.10 (LINN).
Herbs, annual. Stems 2–5(–6) dm, erect, simple below, rigidly branched at or above middle. Basal leaves short-petiolate, oblanceolate, 2–7 cm x 0.5–1.5 cm, pinnatifid, runcinate, sinuate, or dentate, withered by anthesis; cauline leaves below branches sessile, oblong to lanceolate, (1–)1.5–6(–8) x (0.3–)0.5–2(–2.5) cm, base sagittate to amplexicaul or auriculate, margin entire or denticulate, apex acute or obtuse; leaves of branches similar but progressively smaller upwards, entire. Racemes with numerous flowers; fruiting pedicels 3–5 mm, stout, appressed to rachis, much wider distally. Sepals oblong to ovate, 2.5–3.5 x 0.6–1.4 mm; petals yellow, oblong to oblanceolate, 3–5 x 0.7–1.4 mm, attenuate to base, obtuse at apex; filaments 2.5–3.7 mm; anthers oblong, 0.5–0.7 mm. Fruit obpyriform to clavate-obcordate, 4.5–7.5(–8.5) x 2.5–4.5(–5) mm, appressed to rachis; style (0.8–)1.2–2 mm. Seeds brown, oblong to ovoid, 2–3 x 1–2 mm. 2n = 14.
Habitat: roadsides, waste grounds, disturbed sites.
Distribution: s Europe (Albania, Bosnia and Herzegovenia, Bulgaria, Czech Republic, France, Germany, Greece, Hungary, Italy, Romania, Russia, Serbia, Slovak Republic, Slovenia, Spain, Ukraine);SW and C Asia (Armenia, Azerbaijan, Georgia, Iran, Iraq, Israel, Jordan, Lebanon, Syria, Turkey); introduced into South Africa, E Asia (Japan, Korea), Australia, and the United States (Texas, Virginia).