Rorippa sinuata (Nutt.) Hitchc.
Spreading Yellow Cress
Family - Brassicaceae
Stems - Decumbent to prostrate, often rooting at nodes, herbaceous, multiple from thin rhizomes, glabrous or with vesicular hairs.
Leaves - Alternate, pinnately lobed, clasping or not, auriculate or not, to 8cm long, 2.5cm broad, glabrous or with few vesicular hairs. Lobes shallow toothed to entire.
Inflorescence - Terminal and axillary racemes elongating in fruit to 20cm long. Pedicels 5mm long in flower, to +1cm in fruit, typically at right angles to axis and curved in fruit.
Flowers - Petals 4, yellow, glabrous, to 5mm long, +2mm broad, narrowed at base to claw. Stamens 6, erect. Filaments to +3mm long, greenish-yellow, glabrous. Anthers yellow, 1.1mm broad. Ovary green, glabrous, 3mm long, slightly compressed. Style 1mm long, persistent in fruit. Stigma capitate. Sepals 4, greenish-yellow, to 4mm long, 1.8mm broad at base, glabrous, with scarious margins, erect to spreading, acute. Siliques to 6mm long, few seeded, 2-valved, cylindrical, beaked with persistent style, ascending (curving) towards the axis of the inflorescence.
Flowering - April - July.
Habitat - Moist ground of flood plains, , railroads, disturbed sites.
Origin - Native to U.S.
Other info. - The fruits of this genus are cylindrical and appear "short and fat" compared to other genus of the family. Technically they are classified as siliques but could be called silicles also. Some of the species in this genus can be difficult to distinguish.
Photographs taken at the Kansas City Zoo, 6-22-00.