Menyanthaceae, the Bogbean or Buckbean Family
Nymphoides is a genus of approximately 50 species of aquatic plants distributed in temperate, subtropical and tropical regions almost worldwide. Six species occur in Florida. Two of these (N. aquatica and N. cordata) are native, while three (N. cristata, N. indica and N. peltata) were introduced to Florida through the aquatic plants trade and subsequently escaped from cultivation. The sixth (N. grayana) is native to the Caribbean and the Bahamas and is not often found in the plant trade. This species likely arrived in Florida by natural means, such as seeds floating or being carried by waterfowl or migrating birds.
Crested floating heart and yellow floating heart are rhizomatous perennial aquatics that are usually rooted in the substrate of shallow waters, but small vegetative propagules may be free-floating. The long, narrow, unbranched stems are submersed. The leaves typically float on the water surface, but a few leaves may also be submersed. Most leaves are alternately arranged. In yellow floating heart, leaves toward the end of the stem may be opposite or subopposite. The leaf blades are somewhat leathery, ovate to circular in outline, with a cordate (heart-shaped) base and indistinct, palmate venation. Leaves are often reddish or purplish below. The leaf margins are usually entire (and often tinged red) in crested floating heart, but slightly wavy and shallowly scalloped in yellow floating heart. Clusters of flowers are borne at the distal stem nodes. The flowers develop under water and rise above the surface at maturity. The corolla of crested floating heart is white with a yellow eye and is ½-¾ inch wide. Each petal has a ruffled crest running lengthwise down the center. The petal margins are slightly wavy to ruffled, sometimes fringed distally. Yellow floating heart has a corolla that is golden yellow in color and measures 1 to 1½ inch wide, with finely fringed petal margins. The fruit of crested floating heart are ellipsoid to subglobose capsules to ¼ inch long, which contain up to 20 tiny (less than 1/20 inch long) tuberculate (with numerous small rounded warts) seeds. The capsules of yellow floating heart are ellipsoid to ovoid with a distinct distal beak. Measuring up to an inch long, they bear numerous, larger (⅙ to ¼ inch long) seeds, which are elliptic in shape, flattened and have densely ciliate margins.
Crested floating heart is native to subtropical and tropical regions of eastern India, Vietnam and southern China, while yellow floating heart is native to temperate Asia and Europe. Both species are typically found in still, shallow waters, such as ponds, lakes and canals, but may also occur in slow-moving streams, and have been reported as weeds in rice fields. Yellow floating heart has escaped from cultivation and naturalized in parts of the eastern, central and western United States, as well as eastern Canada. The naturalized range for crested floating heart is somewhat more restricted. It has been reported from Florida, South Carolina, Mississippi and Texas.
Crested floating heart has been vouchered with herbarium specimens from several, scattered Florida counties, ranging from Broward to St. Johns. In Florida, yellow floating heart has a very restricted distribution.
The name Nymphoides means “resembling Nymphaea” (the water lily), but the two genera are fairly easy to distinguish. True water lilies are usually larger-statured plants with angled leaf bases and showy, rose- or camellia-like flowers that have four sepals, eight to many petals and numerous prominent stamens forming a cluster. Floating hearts, on the other hand, are smaller plants with rounded leaf bases and flowers consisting of five sepals, five petals and five stamens that are separate (not clustered together). Of the six Nymphoides species native or naturalized in Florida, yellow floating heart is the only one with flowers that are consistently golden yellow in color with petals fringed by fine hairs. .Nymphoides grayana also bears flowers that are solid yellow, but has petal margins with long, prominent hairs. Crested floating heart can be distinguished by the longitudinal, ruffled crest or fold running down the center of each petal.
Species | Origin | Flowers | Leaves |
Nymphoides aquatica big floating heart | native (eastern and central USA) | white with yellow center, ⅓-¾ inch wide | ovate to kidney-shaped, 2-6 inch long, veins prominent above, underside scabrous |
Nymphoides cordata little floating heart | native (eastern USA and Canada) | white to cream with yellow center, ⅕-⅖ inch wide | cordate-ovate, 1¼-2¾ inches long, often variegated with reddish-purple above, underside smooth |
Nymphoides cristata crested floating heart | introduced (Asia) | white with a yellow center, ½-¾ inch wide, petals with a ruffled crest down the center | ovate-orbicular to suborbicular, 1¼-4 inches long, underside densely glandular and scabrous, margin entire and often tinged red (sometimes entire upper surface with red markings) |
Nymphoides grayana Gray’s floating heart | natural range expansion, previously mistaken as yellow N. indica Caribbean, Bahamas | pure yellow, 1-1½ - inches wide, petals prominently fimbriate (with slender, hair-like projections) along the margins | suborbicular , 2 ½ - 3 inches long, with overlapping lobes, dull green above, purple below |
Nymphoides indica water snowflake | introduced (Asia, Africa, Australia, tropical America) | white with yellow center, 1-1½ inches wide, petals prominently fimbriate along the margins | ovate-orbicular to subcordate, 1¼-7 inches long, underside densely glandular and scabrous, margin entire |
Nymphoides peltata yellow floating heart | introduced (Europe, temperate Asia) | golden yellow, 1-1½ inches wide, petals with finely fringed margins | suborbicular, 1¼-6 inches long, underside densely glandular and often purplish, margin slightly wavy and usually shallowly scalloped |
Both species are very successful at vegetative (asexual) reproduction. In addition to spreading by rhizomes, new plants are generated by the formation of adventitious roots on separated leaves and stem fragments. In crested floating heart, bulbils often form on the undersides of the leaves, and when separated from the leaf, each bulbil grows into a new plant. Fragmentation and dispersal may be facilitated by boats and flooding. Fruit and seed formation appears to be uncommon in Florida populations of crested floating heart. Yellow floating heart, on the other hand, reproduces readily by seed. The hairs on the seed margins help them float and attach to the feathers of waterfowl, which can disperse the seed over longer distances.
These aggressively growing species form dense mats of vegetation that crowd out native aquatic plant species and have negative impacts on water quality and fish and wildlife habitat. Recreational activities are also impacted since extensive networks of submersed stems can entangle boat motors, water skis, fishing lines and swimmers.