Ludwigia inclinata

Ludwigia inclinata is a highly variable herb from Central and South America, usually found growing emersed or submersed on the beds of dried ponds or lakes, either submerged or with emergent stems. The verticillate forms, of which several are known, are among the most highly prized aquarium plants in the trade. They include Ludwigia inclinata var. verticillata "Pantanal" and Ludwigia inclinata var. verticillata "Cuba". When grown to its full height, Ludwigia inclinata var. verticillata "Pantanal" is one of the most beautiful stem plants....read more on Wikipedia.