Ludwigia alternifolia
A branched, bushy 2-4' plant with smooth, reddish stems. The alternate leaves are narrow and pointed. The 1/2" flowers are on short stalks in the upper leaf axils. The 4 roundish yellow petals fall quickly, leaving 4 broad sepals about as long as the petals. The characteristic seed capsule is box-like and rounded at the base. Blooms June-September in swamps, other wet areas.