Taxonomic name: Nymphoides peltata (Gmel.) O. Kuntze
Synonyms: Limnanthemum peltatum Gmel., Nymphoides nymphaeoides (L.) Britt.
Common names: asaza (Japanese), entire marshwort (New Zealand), floating heart (English), fringed water lily (English), xing cai (Chinese), yellow floatingheart (English)
Organism type: aquatic plant
Nymphoides peltata is usually introduced as an aquatic ornament though it is not the case in its native area. However, the sale and distribution of Nymphoides peltata is slowing becoming more controlled. It can become extremely invasive in shallow, slow-moving swamps, rivers, lakes and ponds. Currently there is little information available on the control of Nymphoides peltata but hand removal for small infestations and herbicides for larger infestations seem to be the most effective.
According to NWCB (2003), N. peltata is an “aquatic, bottom-rooted perennial with long branched stolons extending up to one metre or more and lie just beneath the waters surface. The node on the stolons typically produces a plant and many thread-like roots. The floating heart to almost circular shaped leaves are 3-10cm long on long stalks, and they arise from creeping underwater rhizomes. The leaves are frequently purplish underneath, with slightly wavy, shallowly scalloped margins. The flowers are bright yellow, 5-petaled and 3-4cm in diameter. The flowers are held above the water surface on long stalks, with one to several flowers per stalk. The flower edges are distinctively fringed (its common name is Fringed water lily). The fruit is a capsule up to 2.5cm long containing numerous seeds. The seeds are flat, oval and about 3.5mm long with hairy edges.”
lakes, riparian zones, water courses, wetlands
According to NWCB (2003), N. peltata prefers slow moving rivers, lakes, reservoirs, ponds and swamps 0.5 to 4 metres deep. It can also grow on damp mud. It is usually restricted to a belt between the helophytes and other floating leaved and submerged macrophytes at deeper sites.
WSDE (2003) states that “like other floating leaved plants, yellow floating heart / fringed water lily grows in dense patches, excluding native species and even creating stagnant areas with low oxygen levels underneath the floating mats. The structural complexity of its mats make it difficult to fish, water ski, swim, or even paddle a canoe through. NWCB (2003) would add “fish and wildlife habitat, recreation and water quality is negatively impacted when the dense mats of N. peltata outcompete native and beneficial plant species. Another problem is that "Hitchiker" plants, such as the invasive Hydrilla verticillata (hydrilla), can be introduced to an area with N. peltata when mail-ordered.
Yellow floating heart can be a popular aquatic garden ornamental for outdoor water gardens (NWCB, 2003).
With its floating leaves N. peltata effects a vigorous competition for light, notably with phytoplankton, and it seems not to suffer from turbid waters in the numerous eutrophic waterbodies it colonises.
Native range: Asia-temperate, Asia-tropical, and Europe (USDA-ARS NGRP, 2002).
Known introduced range: North America (USDA-ARS NGRP, 2002) and New Zealand (NWCB, 2003).
Introduction pathways to new locations
For ornamental purposes: According to NWCB (2003), "N. peltata popular aquatic garden ornamental for outdoor water gardens."
Internet sales/postal services: According to NWCB (2003), "N. peltata is sometimes is mail-ordered.
Local dispersal methods
Garden escape/garden waste: According to NWCB (2003), N. peltata is used as in outdoor water garden. This would allow it to be spread to new areas by water (during rain events) and/or by waterfowl.
On animals: According to NWCB (2003) these hairs also aid their attachment to waterfowl, which can also be a means of spreading this plant to new areas.
Water currents: The hairs on the seeds help the seeds float to new locations, according to NWCB (2003).
Preventative measures: New Zealand and the US states of Washington, Maine, New Hampshire, Connecticut, Vermont, South Carolina, Canada are also attempting to use regulations to control the invasive.
Integrated management: According to DECFW, VANR, and TNCV (1998), “little information is available on the control of N. peltata. Based on the plant’s characteristics, mechanical and hand removal would most likely be effective. It is not known whether biological or chemical controls are effective on N. peltata. According to WSDE (2003), “N. peltata has a similar growth habit to the fragrant waterlily and it is expected that methods used to manage waterlilies would also be effective on yellow floating heart. Waterlilies (and yellow floating heart) can be controlled by cutting, harvesting, covering with bottom barrier materials, and aquatic herbicides (Rodeo®). Grass carp do not eat waterlilies in Washington and it is not known if they would readily eat N. peltata.” According to NWCB (2003), “New Zealand information suggests that hand clearing is possible with small infestations and herbicides need to be used for larger infestations.”
The plant, as in most of rooted-macrophytes, functions as an important nutrient pump from the sediment. Nutrients are then partitioned between the decomposition pathway and the resorption by the rhizomes during senescence of the above-ground organs.
NWCB (2003) writes that “N. peltata reproduces by seeds and vegetatively by broken stems. Seed hairs help the seeds float and aid their attachment to waterfowl, which can be a vector in spreading this plant to new areas. However hydrochory seems to be the main dispersal mode of seeds. Viable seeds are produced abundantly and germinate readily. Broken leaves with attached stem parts will also form new plants.”
The growing season ranges from April/May to late October. Biomass of above-ground organs peaks in late Summer and represents up to 50-60% of total plant biomass. As in most floating-leaved plants, primary production is relatively high and mainly results from high turn over rates (3,4-7,3). Leaf life span varies from 23 to 43 days in relation to several factors (substrate, water level fluctuations, degree of exposure to wind and wave action). The plant overwinters as dormant tuberous rhizomes.
Reviewed by: Jean-Marc Paillisson, UMR CNRS 6553 Ecobio - Population and Conservation Biology. University of Rennes - France.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 20 September 2006