Hydrocleys, genus of perennial aquatic plants of the family Alismataceae (formerly placed in Limnocharitaceae), consisting of five species, all native to tropical America. These herbaceous plants have floating, emergent, or submersed leaves and commonly employ stolons or plantlets (small offshoots) for asexual reproduction. The radially symmetric flowers are somewhat showy and produce follicular fruits (dry fruits that split open along one side). The water poppy (Hydrocleys nymphoides), with yellow flowers about 5 cm (2 inches) across, is the only cultivated species and is often grown in ponds and aquariums.