Marshwort
Botanical Name
Nymphoides montana
Family
Menyanthaceae
Also known as
Entire marshwort
Where is it originally from?
Victoria and New South Wales, Australia
What does it look like?
Water lily-like perennial aquatic with floating, bright green, heart-shaped leaves (up to 10cm across, and slightly longer than wide) with often pinkish undersides and stems (stolons) that are long and branched, and float just below the water surface. Leaves, roots and flowers grow in clusters from nodes along the stem. Roots are suspended in deeper water. Flowers (25-35 mm wide) with five bright yellow petals with fringed wing margins are produced from November to April, held above the water on long (7cm) stalks, with each stalk bearing about 2-7 flowers. Seeds have not been observed in NZ.
Are there any similar species?
Fringed water lily (Nymphoides peltata) has leaves with scalloped margins, compared to smooth margins of marshwort. Yellow water lily (Nuphar lutea) has much larger leaves and very thick spongy stems. Water lily (Nymphaea alba) has much larger leaves with distinct mid veins. Water poppy (Hydrocleys nymphoides) has an inflated mid vein on the underside of the leaf.
Why is it weedy?
Grows rapidly, forming dense floating mats of foliage that fill waterways.
How does it spread?
Spreads by long, creeping stems and by fragments of plant taking root. Fragments can spread by water currents, boats and fishing nets.
What damage does it do?
Rapidly colonises shallow water, forming dense mats inpeding drainage and shading out other aquatic plants, blocking access to water and interfering with recreational activities.
Which habitats is it likely to invade?
Lake margins and ponds (or other water bodies) in still conditions.
What can I do to get rid of it?
Contact your regional council to determine the status of this species and responsibility for control and/or advice on control.
What can I do to stop it coming back?
Monitor the site and report any regrowth to your regional council.
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