has spread from Europe and Asia across most areas of the US, especially west of the Rocky Mountains. The plant grows in or near water; its stems are light and hollow, allowing them to float on the surface of streams and lakes. Leaves are edible, and the plant has a long history of cultivation as a salad vegetable. Stems and leaves are smooth and usually hairless. Leaves are divided into an odd number of non-overlapping leaflets, somewhat variable in shape, often with slightly rippled or toothed edges.
The inflorescence is a densely-packed, spherical cluster, typical of the brassicaceae family; flowers have four unfused, greenish-yellow sepals and four white petals, slightly unequally spaced, with bilateral rather than radial symmetry. The flower center contains six stamens, about the same height as the petals, and a style, which gradually lengthens after pollination to form the slender fruit.