Ludwigia peploides

Native to parts of the Americas, eastern Asia, and Australia, this perennial aquatic herb is commonly called creeping waterprimrose. Its trailing stems spread across shallow water and root at the nodes, while flowering shoots rise above the surface. Bright yellow flowers usually have five petals. Stems and stem fragments can establish new plants, allowing colonies to form dense floating or emergent mats along sheltered water margins. It is invasive in France, where colonies can obstruct waterways and crowd out other aquatic plants. Photographed in Colombia.