1. Barbarea verna (Mill.) Asch. (early winter cress, American cress)

Map 1317

Stems (10–)25–80 cm long. Leaves 2–15 cm long, the basal and lowermost stem leaves with the blade oblanceolate, deeply pinnately divided with (3–)6–10 lateral segments or lobes and a large, circular to oval, terminal lobe, the median and upper stem leaves oblanceolate, irregularly lobed, toothed, or nearly entire. Sepals 3–5 mm long. Petals 5–8 mm long. Styles 0.2–2.0 mm long. Fruits (4.5–)5.5–7.0(–8.0) cm long, the stalks 3–6 mm long, nearly as thick as the fruits. Ovules or seeds (34–)38–48(–52) per ovary or fruit, the seeds 1.5–2.5 mm long, more or less oblong in outline, broadly elliptic in cross-section, slightly flattened. 2n=16. April–June.

Introduced, uncommon, known thus far only from a single historical collection from Iron County (native of Europe, Asia; introduced widely in North America, Africa, Australia). Habitat unknown, but presumably open, disturbed areas.

The Iron County record originally was misdetermined as B. vulgaris and was discovered during the present research. The species occurs in most surrounding states and thus will likely be found elsewhere in Missouri in the future.