Pontederia Cordata, also called Pickerel Weed or Heart-leaved Pickerel Weed is part of the Pontederiaceae. A marginal habitat perennial it flowers with small erect spikes of violet blue tubular flowers in late summer. Once flowers gets to seed stage the stems bend to get submersed.
Pontederia Cordata is native to North America and Caribbean and south all the way to Argentina, it is a wetland plant. It is deciduous, clump-forming herbaceous perennial that needs full sun. Plant it in shallow water in fertile but poorly drained soil. You can propogate by seeds or division in spring.