Rorippa sylvestris (L.) Besser

Rorippa species are aquatic or mesic, annual, biennial or perennial herbs, glabrous or pubescent with simple trichomes, not scapose. Rootstocks rhizomatous, caudex sometimes present. Stem erect or prostrate, ascending, leafy, simple or branched. Basal leaves simple, rosulate or not, usually withered before flowering, obovate-oblanceolate to oblong, base cuneate to attentuate, margin entire, sinuate dentate, lyrate to pinnatisect, apex acute, petiolate, cauline leaves usually gradually smaller, base cuneate, margin entire, dentate to pinnatisect, petiole short to sessile. Inflorescence racemes, many flowered, considerably elongated in fruit, ebracteate, rarely bracteate. Flowers bisexual, yellow, white or pink, pedicel erect or slightly curved, divaricate or reflexed, slender, ascending, sepals 4, erect or spreading, linear ovate-oblong, margin membranous, inner lateral pair base rarely saccate, petals 4 or rarely absent, obovate-oblanceolate to spathulate, margins entire, apex obtuse or emarginate, claw distinct, usually shorter than sepals. Stamens 6 rarely 4, tetradynamous, filaments not dilated near the base, anthers ovate-oblong, apex obtuse rarely apiculate, nectar glands 4 confluent, usually subtending the bases of stamens, median glands present. Ovary superior, bicarpellary, ovules 10-250. Fruit siliqua or silicles, dehiscent, linear cylindrical, ellipsoid or obovoid, sessile or shortly stipitate, terete, erect or slightly curved, latiseptate, smooth or torulose, valves chartaceous with prominent or obscurely veined, replum rounded, septum complete, style obsolete or short, stigma capitate, entire or slightly bilobed. Seeds usually biseriate, rarely uniseriate, brown, plump, elliposid, oblong-ovoid, not winged or rarely winged, minutely reticulate, mucilaginous or not when soaked, cotyledons accumbent.

Rorippa species flowers are complete, bisexual, i.e., with functional male (androecium) and female (gynoecium), including stamens, carpels and ovary. Pollination is entomophilous i.e., by insects, or cleistogamy i.e., by self or allogamy i.e., by cross pollination. Flowering/Fruiting: May—August.

Seeds may be dispersed by autochory i.e., self dispersal, anemochory i.e., wind dispersal, zoochory i.e., dispersal by birds or animals, anthropochory i.e., dispersal by humans.

Perennial herbs, usually glabrous or sparsely pubescent with simple trichomes, stoloniferous, about 10-80 cm tall. Stem glabrous, procumbent or decumbent, ascending, simple or branched from the base. Basal leaves not in rosulate, usually withered very soon before flowering, obovate-oblanceolate in outline, about 3-15 x 0.8-4.5 cm across, margin deeply pinnatisect, lateral lobes 3-6 pairs, gradually becoming larger towards the apex, lobes obovate to oblong, margins coarsely sinuate dentate to serrate, petiole short, cauline leaves similar to basal, gradually smaller, petiole subsessile to sessile, usually uppermost leaves not lobed. Inflorescence raceme corymbs, 10-50 flowered, about 5-30 cm long, elongated in fruit, ebracteate. Flowers bisexual, yellow, pedicel erect, divaricate, slender, ascending, about 4-10 mm long, sepals 4, erect, linear oblong, ascending or spreading, margin membranous, inner lateral pair base rarely saccate, about 2-3 x 0.8-1.5 mm across, petals 4, obovate-spathulate, margins entire, apex emarginate, about 3-5.5 x 1.5-2.5 mm across. Stamens 6, tetradynamous, filaments not dilated near the base, about 2-3.5 mm long, anthers oblong, about 0.7-1 mm long, apex obtuse. Ovary superior, bicarpellary, ovules 24-90. Fruit siliqua, dehiscent, linear cylindrical, about 10-25 x 1-1.3 mm across, erect or slightly curved, base and apex acute, smooth, valves chartaceous with prominent midvein, replum rounded, septum complete, style 0.5-1 mm long, stigma capitate, subentire or slightly bilobed. Seeds uniseriate or sub-biseriate, reddish brown, plump, orbicular, ovate-ovoid, about 0.5-0.9 mm long, minutely reticulate, colliculate, cotyledons accumbent.

Rorippa species are susceptible to various insect pests, virus, mildews and moulds.

Meadows, waste places, nurseries, along streams, near cultivated fields and wet lands, altitude up to 2000 m.

Least Concern (IUCN).

Troublesome weed.