Lysimachia congestiflora

Native from Nepal through China and northern Indochina, this low-growing perennial herb forms a creeping mat with stems that root at the nodes. Yellow, cup-shaped flowers have five petals and a red eye, appearing in dense terminal clusters. Plants grow about three to six inches tall and occur naturally along damp forest margins, roadsides, rice paddies, and ditches. Photographed in Colombia.