Perennial herb with thin rhizomes 10 - 40 cm tall Leaves: alternate, pinnately divided, sometimes clasping, 3 - 8 cm long, 0.5 - 1.5 cm wide, reverse egg-shaped or oblong, bases sometimes lobed, tips usually rounded, sometimes shallowly toothed, sometimes with some bladder-like (vesicular) hairs. Leaf segments commonly five to seven pairs. Flowers: in branched clusters (racemes), which are borne terminally and axillary on the stems. Flower stalks 5 mm long and at right angles to the axis. Sepals four, upright to spreading, greenish yellow, to 4 mm long, 1.8 mm wide at base, tips pointed. Petals four, light yellow, 3.5 - 5.5 mm long, over 2 mm wide, longer than sepals, bases narrowed. Stamens six, upright. Anthers yellow. Fruit: a pod (silique), ascending, 5 - 12 mm long, 1.5 - 2 mm wide, cylindrical, often with bladder-like (vesicular) hairs, two-valved, on curved stalks to 1 cm long, with a 1.3 - 2.5 mm long beak. Seeds few. Stems: multiple, decumbent to prostrate, sometimes with bladder-like (vesicular) hairs, often rooting at the nodes.
Similar species: No information at this time.
Flowering: April to July
Habitat and ecology: Typically found in moist to wet areas, especially along rivers, but rare in the Chicago Region. Two specimens from Cook and DuPage counties in Illinois, both found growing along a railroad, are believed to be introductions.
Occurence in the Chicago region: native
Etymology: Rorippa possibly comes from the Latin roro, meaning "to be moist," and ripa, meaning riverbank. Sinuata means "with a wavy margin."
Perennial 1-4 dm, usually with several ascending branches from near the base, the stem and lower surface (or at least the midrib) of the lvs sparsely to densely beset with small, vesicular, hemispherical trichomes that may be collapsed and scale- like in dried specimens; lvs all cauline, 3-8 נ0.5-1.5 cm, oblanceolate or oblong, auriculate-clasping or not, pinnatifid, the segments commonly 5-7 pairs, spreading or ascending, usually obtuse, entire or with a few teeth, separated by rounded sinuses; lateral sep somewhat saccate at base; pet light yellow, 3.5-5.5 mm, surpassing the sep; mature pedicels slender, ascending to recurved, 5-9 mm; frs subterete, 5-12 נ1.5-2 mm, straight or upcurved, often beset with vesicular trichomes, abruptly narrowed to a slender stylar beak 1.3-2.5 mm; 2n=16. Moist, especially sandy soil, fields, and shores; Ill. to Alta. and Wash., s. to Ark., Tex., and Calif., and occasionally adventive eastward. Apr.-July. (Radicula s.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.