Ludwigia octovalvis

Native across tropical and subtropical regions of the world, this wetland plant grows as a branching herb or subshrub. Robust stems may become woody at the base and reach about 13 feet tall. Yellow flowers have four petals and eight stamens. It occupies damp ground and shallow water, including marshes, stream margins, and drainage ditches. It reproduces by seed and can flower throughout the year in tropical conditions. It can be a serious weed in rice fields in Asia, Latin America and the Caribbean. Photographed in Colombia.