|Botanical Name||Nymphoides geminata|
|Origin||Victoria, New South Wales|
DescriptionEntire marshwort is a robust, bottom-rooted perennial which has long branched running stems which extend for several metres and lie just beneath the water surface. The leaves are broadly ovate to rounded and are somewhat smaller than the leaves of other water lilies being 30mm to 80mm long.
Where is it found?It is most clearly distinguished form other floating aquatic plants by its bright yellow 5 lobed flowers, which are borne above the water surface on long stalks arising in pairs from short leafless side stems. The flowers are 25 to 35mm wide and have distinctive fringed wings around the top of the margins of the petals and a fringed perimeter around the top of the corolla tube. Flowers can be observed from November through to April, although they only last for one day.
Why is it a problem?Entire marshwort is an invasive aquatic plant with the ability to impede drainage or block waterways. It can block access to water, be a nuisance to recreational activities and is a threat to wetlands by displacing native species.
How does it spread?Entire marshwort has the ability to rapidly spread from one area to another by fragmentation. The plant has the unusual ability to grow roots from detached leaves and this is how new infestations are formed. Detached stems and leaves are spread by water currents, on boats and sometimes in fishing nets. Localised spread or increases in size of established infestations occurs by running stems (stolons) extending outwards, several metres at a time, from the parent infestation. Seeds have not been observed in New Zealand but have been reported from Australia.
How do I get rid of it?
All sightings of this plant should be reported to a Pest Plants Officer who will organise the clearance of the plant.
Smaller infestations are cleared by hand whilst larger sites are controlled by the laying of black weed mat.
All plants removed by hand must be disposed of away from water courses.
Spraying with Glyphosate is an effective defoliant however repeated applications will be necessary.
Entire marshwort is an Eradication Pest plant in the Bay of Plenty.
This native of Australia was first recorded at a field site in New Zealand in 1976. It has appeared at several dozen sites throughout the country since then, due mainly to the plant being sold for use in ornamental ponds. (Sale of the plant has been restricted for several years).
For further information on Marshwort please refer to Environment Bay of Plenty's Fact Sheet on Aquatic Pest Plants.
This plant is prohibited from propagation, sale and distribution within New Zealand!