Greater duckweed
Spirodela polyrhiza · Araceae
The gardener's calendar
Ideal time to plant greater duckweed: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Botanical family
- Araceae
- Plant type
- Floating aquatic
- Foliage
- Evergreen
- Adult size
- 2 to 8 mm diameter per frond
- Growth
- Very fast
- Hardiness
- Moderate (0 to 15°C depending on conditions)
- Origin
- Cosmopolitan (all continents)
- Natural habitat
- Fresh stagnant or slow-moving waters
Care
Watering and submersion
Duckweed floats naturally at the surface and doesn't need traditional watering. Keep the water level constant in your pond or aquarium, avoiding sudden fluctuations. Avoid strong currents that would fragment the colonies and reduce their density.
Light exposure
Place it in full light or partial shade, ideally 4 to 6 hours of direct sunlight daily. It tolerates indoor environments well when lit with horticultural LED lamps. Insufficient light slows growth and can promote abnormal root elongation.
Nutrition and fertilizer
In poor water conditions, add a diluted complete fertilizer (macro and micronutrients) every 2 to 3 weeks in small amounts. In fish-populated ponds, natural nitrate input is usually sufficient. Avoid overdosing, which encourages filamentous algae.
Substrate and water
No substrate needed: the plant floats freely. Water should be soft to moderately hard (pH 6.5 to 8.0). It adapts well to aquariums and ponds as long as the water isn't polluted by detergents or heavy metals.
Pruning and management
Regularly thin out colonies to prevent total surface coverage and maintain light penetration. Remove fronds by hand or with a small net. This pruning stimulates branching and keeps the plant in good health.
Pests and prevention
Seldom affected by disease. Watch out for aquatic snails that can nibble the roots. Monitor for green or red algae that compete with duckweed. Regular maintenance and moderate water circulation limit these issues.
Did you know?
Spirodela polyrhiza is one of the world's smallest flowering plants and reproduces mainly through fragmentation: each frond can generate a genetically identical descendant. It's so invasive in some temperate ecosystems that it's become a scientific model for studying population dynamics in aquatic plant communities.
Where to buy it
Best planted in spring or autumn, away from frost and heatwaves. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September, October.
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Tips generated and checked by Viridia — adapt them to your local climate.