Rorippa sessiliflora


Rorippa sessiliflora (sessile-flowered yellow cress or stalkless yellow cress) is a native herbaceous annual in the mustard family (Brassicaceae). Leaves are alternate, simple, with pinnate major veins and lower leaves often dissected. Flowers are produced in racemes but with very short to no peduncles and have four yellow sepals and four stamens. Petals are lacking or very small if present. The fruit is a terete silique. The mustard family has some distinct characteristics of four sepals, four petals and four stamens with the flower especially the petals looking like a cross hence the old name of Cruciferae. The inflorescence is a raceme and the fruit a dry dehiscent one that splits into two parts with a partition between. The partition remains on the plant as a white distinct structure and is called the septum. If the fruit is more than 3 times as long as wide, it is called a silique as in this genus and also mustard. But if the fruit is less than three times as long as wide and thus roundish, it is called a silicle as in peppergrass or shepherd’s purse. Found this plant at Bundick Lake during the Graminoid Plant ID Class on Wed. No caterpillars reported to eat this species but three butterflies (Checkered White, Cabbage White, and Great Southern White) plus four moths (Diamondback Moth, salt Marsh Moth. The Gem, and Variegated Cutworm Moth) are reported to eat other species in this genus or the genus.