Ottelia alismoides Care Guide
Ottelia alismoides (duck lettuce) is an aquatic plant of the family Hydrocharitaceae with rosettes of broad leaves and white floating flowers, native to Asia and northern Australia.
Compiled by Aquairi from published sources · Published · Updated
Overview
Ottelia alismoides, known as duck lettuce, is an aquatic plant in the family Hydrocharitaceae with the binomial authority (L.) Pers. It forms rosettes of broad, heart-shaped leaves and produces white flowers that float at the surface. The species is notable for unusual carbon metabolism mechanisms and has had its genome sequenced for research and conservation.
Taxonomy
- Family: Hydrocharitaceae
- Genus: Ottelia
- Scientific name: Ottelia alismoides
- Common name: Duck lettuce
Origin
The species is native to Asia and northern Australia. It is widespread but listed as endangered in China and Japan owing to habitat loss, and is regarded as an invasive weed in parts of America.
Habitat
It grows in still and slow-moving fresh waters such as rice paddies and ponds, rooting in the substrate and forming submerged rosettes whose flowers reach the surface.
Tank requirements
- Temperature: 22-28 °C (optimal 22-26 °C)
- pH: 6.0-7.8
- GH: 4-16 °dGH
- Lighting: high
- CO2: not strictly required; tolerates 10-40 mg/L
- Substrate: nutrient-rich
- Maximum height: about 60 cm
- Placement: background
Planting & care
The plant is rooted in nutrient-rich substrate and given strong light. Growth can be fast under good conditions. Its rosette habit and surface flowers make it a striking background species, though it benefits from stable parameters.
Propagation
Propagation is by seed; the plant can also be increased by splitting and removing daughter plants.
Difficulty
The species is rated intermediate. Strong light and a rich substrate are needed for healthy rosette growth.
Conservation status
IUCN Red List: Least Concern (3.1), though regional populations in China and Japan are endangered.
Propagating Ottelia alismoides (Duck Lettuce)
Overview
Ottelia alismoides, known as duck lettuce, is a submerged macrophyte in the family Hydrocharitaceae, native to Asia and northern Australia. It grows as a rosette of broad leaves and is widely distributed across tropical and warmer regions, occurring along lake shorelines, in marsh ponds, irrigation ditches and stream margins in water roughly 0.05 to 1 m deep. While listed as Least Concern overall, it is endangered in China and Japan through habitat loss, yet behaves as an invasive weed in America.
Reproductive Mode / Propagation Method (Seeds)
This species lacks specialised organs for vegetative reproduction, so population recruitment and expansion depend solely on sexual reproduction. In practice that means propagation runs through flowering and seed set: as with the genus Ottelia, flowers are held in herbaceous bracts and develop into tapering, winged fruits whose six-chambered ovaries contain many small oblong seeds. For the aquarist this makes seeds the realistic route, rather than cuttings or runners.
Step-by-Step
- Grow a strong parent rosette in nutrient-rich substrate under bright light so it has the energy reserves to flower.
- Allow flower stems to extend to the water surface, where the flowers open and can set seed.
- After flowering, watch the developing winged fruits and let them ripen on the plant.
- Collect the many small seeds released from the mature fruit.
- Sow seed onto soft, nutrient-rich substrate in shallow, warm water and keep light high until seedlings establish rosettes.
Conditions for Healthy Growth
Treat it as a demanding rosette: high light, a nutrient-rich substrate it can feed through its roots, and warm, stable water in the 22-28 C range with a pH around 6 to 7.8. Shallow water that lets flowers reach the surface mirrors its natural lakeshore, ditch and stream habitat and encourages the flowering needed for seed.
Maintenance
Keep the substrate rich, since this is a root feeder, and maintain strong lighting to sustain dense rosette growth. Often behaving as an annual in the wild, a parent plant may decline after flowering, so timing seed collection around that flowering peak protects the next generation. Remove decaying outer leaves to keep water clean.
Common Challenges
The main difficulty is that there is no vegetative shortcut: if the plant never flowers and sets seed, you cannot multiply it. Insufficient light or a depleted substrate stalls the rosette and prevents flowering. Its status as a rice-paddy and waterway weed elsewhere is a reminder to contain seed and never release it into local waters.