Swamp lily
Botanical name
Ottelia ovalifolia
Family
Hydrocharitaceae (frogbit)
Also known as
Ottelia
Where is it originally from?
Australia
What does it look like?
Surface-floating, bottom-rooted perennial with fibrous roots instead of tubers, rhizomes or runners. Leaves emerge from the root base; ribbon-like submerged juvenile leaves are transparent, and mature leaves (<16 x 6 cm) that float on the water surface are oval, glossy green and fleshy, with 5-7 parallel veins and many cross veins. Solitary, fragile, 3-petalled flowers (5 cm diameter) are white with orange base (Dec-Mar) and there are also closed underwater flowers. Seed capsules (2-5 cm long) contain many seeds.
Are there any similar species?
Cape pondweed (Aponogeton distachyus) is very common, floating leaves 15 x 2 cm, flower a forked white spike. Water poppy (Hydrocleys nymphoides) has fleshy leaves and bright yellow flowers.
Why is it weedy?
Seeds freely, grows in water up to 3 m deep. Forms mats on water surface. Tolerant to hot-cool temperatures. Minor weed, only occasional problem.
How does it spread?
Seed is spread via water flow, contaminated diggers, and probably birds, from ponds, farm dams, and intentional plantings.
What damage does it do?
Can cover still or slow-moving water. Blocks light to native plants below. Impedes oxygenation by wind, affecting water fauna and other plants.
Which habitats is it likely to invade?
Lake margins, shallow ponds, slow streams and rivers.
What can I do to get rid of it?
1. Physical removal - In small ponds/drains rake up and leave to rot away from the water body. Where it’s possible to lower the the pond level weed mat may be used to cover the bottom of the pond to smother the plants and help prevent regrowth.
What can I do to stop it coming back?
In some still and sheltered waterbodies (eg ponds), introducing more wind by removing windbreak on prevailing side may check plant.
Images
