Aquatic and Wetland Vascular Plants of the Northern Great Plains
22. Brassicaceae, the Mustard Family
4. Rorippa Scop. -- Yellow cress6. Rorippa sylvestris (L.) Bess. -- Creeping yellow cress
Rhizomatous and sometimes stoloniferous perennial 2-5 dm tall, glabrous or sparsely hirsute, the stems erect and branched. Leaves short to long-petioled at the base, becoming sessile upward, nonauriculate and nonclasping to auriculate and partly clasping, the blades of cauline leaves pinnately divided to the midrib, 3-12 cm long, 2-5 cm wide, glabrous, the lobes oblong or oblanceolate, entire to irregularly toothed or cleft, the blades of lower and basal leaves often larger with broader lobes. Racemes terminal and axillary, all about the same age or the oldest siliques on the lower portion of terminal racemes. Sepals yellowish-green, 2-2.5 mm long; petals yellow, 2.5-4 mm long, up to 2 mm longer than the sepals. Siliques linear-elongate, 4-10 mm long, 0.5-1 mm wide, mostly 5-10X longer than wide, usually ascending on divergent to deflexed pedicels 5-12 mm long. Jun--Aug. Thus far found only at very scattered locations but potentially spreading to native wetland habitats, e.g., stream banks, shores and ditches; (Intro. to N.Amer. from Europe, now occurring from Newf. to B.C., s to NC, AL, LA, KS, CO and OR).
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