Nymphoides, commonly known as floatingheart, is a genus of approximately 50 aquatic flowering plants in the family Menyanthaceae, order Asterales. The genus name alludes to the resemblance of their floating leaves to those of true water lilies in the genus Nymphaea — the suffix -oides meaning "resembling."
Plants grow with roots submerged in still or slow-moving fresh water, sending up long petioles that hold rounded or heart-shaped leaves flat on the water surface. Flowers are raised just above the water on short stalks. They are sympetalous with typically five lobes; petals may be yellow or white and are often ornamented with fringed lateral wings or covered in small hairs — a characteristic that gives many species a delicate, lacework appearance. The inflorescence takes the form of either an umbellate cluster or a lax raceme, with flowers often borne in pairs at internodal positions along the stem.
The genus has a pantropical to temperate distribution, with the greatest diversity in Australia, and additional species across Africa, Asia, the Americas, and Europe. Notable members include Nymphoides peltata, native to Europe and Asia and widely naturalized as an invasive aquatic weed in North America, and Nymphoides aquatica, the "banana plant" of the southeastern United States, popular in the aquarium trade for its distinctive cluster of banana-shaped tuberous roots. Nymphoides indica, the "water snowflake," is a pantropical species also widely cultivated in aquaria. In Taiwan, the slim stems of Nymphoides hydrophylla are harvested and eaten as a vegetable.
Etymology
The genus name Nymphoides is derived from Nymphaea — the classical genus of water lilies — combined with the Greek suffix -oides, meaning "resembling." The name refers to the floating leaves of Nymphoides species, which closely resemble those of true water lilies, though the two genera belong to unrelated families.
Distribution
Nymphoides has a pantropical to temperate distribution. Species occur on every inhabited continent, with the greatest diversity in Australia. In North America, Nymphoides cordata is native to the northeast and N. aquatica to the southeast; N. peltata, native to Europe and Asia, has naturalized widely in the United States as an invasive aquatic weed. Non-native species including N. cristata and N. indica have also been reported in Florida.
Ecology
Nymphoides species inhabit still or slow-moving fresh water — ponds, lakes, ditches, and sluggish streams — where they root in bottom sediments and extend floating leaves to the surface. The floating leaf canopy shades the water column and provides shelter for aquatic invertebrates and small fish. N. peltata, when introduced outside its native range, can form dense monocultures that displace native macrophytes and alter aquatic habitat structure.
Cultivation
Several Nymphoides species are cultivated as ornamental aquatic plants in ponds and aquaria. Nymphoides aquatica (banana plant) is especially popular in freshwater aquariums because of its unusual cluster of banana-shaped storage roots; it is kept both rooted in substrate and as a floating plant. Nymphoides indica (water snowflake) and the yellow-flowered N. peltata are grown in outdoor water gardens in temperate and warm climates. Where N. peltata is regulated as invasive (much of the United States), planting in open water is restricted.
