TankBud

Giant duckweed

Spirodela polyrhiza

Also known as Greater duckweed, Great duckweed, Common duckmeat, Lemna polyrhiza, Spirodela polyrrhiza

FreshwaterFloatingDivisionFragmentation

Giant duckweed (Spirodela polyrhiza)
Aquarium Plants Factory · Used with permission

Care at a glance

Light
Low light
CO2
No CO₂ needed
Temperature
59–82°F
15–28°C
Max height
0.4 in
1 cm
Growth rate
Fast
Placement
Floating
Type
Floating
pH
6.0–8.0
Hardness
2–18 dGH
Spread
11.8 in (30 cm)
Nutrient uptake
Water column
Growth region
Submersed or emersed
Difficulty
Easy
Family
Araceae
Origin
A free floating duckweed found on still and slow fresh water across most of the world, forming green films on sheltered ponds and backwaters.

Overview

Giant duckweed is a fast floating plant and the larger cousin of common duckweed. It is easy to grow.

Did you know

In cold conditions giant duckweed makes dense, starch-filled buds called turions. They sink to the bottom to overwinter, then rise and sprout again in spring.

Caring for giant duckweed

Float giant duckweed on the surface, with no substrate or CO2 needed. Low light is enough, and it handles 59 to 82°F (15 to 28°C).

It takes its food from the water and soaks up nitrate and phosphate quickly, which makes it useful for controlling nutrients. It also shades the tank and clogs filters, so skim off the excess often.

Giant duckweed grows fast, budding off new plants, and pieces that break away keep growing. Once a few fronds are in a tank, it is almost impossible to remove completely.

Good to know

Giant duckweed is one of the duckweeds, which are among the smallest and simplest flowering plants. Each plant is reduced to a flat frond and roots, with tiny flowers that are rarely seen. Its rounded fronds reach about a centimeter across, bright green on top and often reddish purple underneath. Each frond trails a small cluster of roots, which sets Spirodela polyrhiza apart from Lemna, with its single root.

In the wild

Giant duckweed floats on still and slow fresh water across most of the world. It forms green films on sheltered ponds and backwaters, multiplying fast into a living blanket across calm water.

Common questions

Does giant duckweed need to be planted in the substrate?

No. Giant duckweed floats at the surface and takes its nutrients straight from the water.

Does giant duckweed need CO2?

No. Giant duckweed grows well without added CO2 and suits a low-tech tank.

How much light does giant duckweed need?

Giant duckweed is a low-light plant, and the light that comes with a standard tank kit is enough for it.

How do you propagate giant duckweed?

Giant duckweed propagates by division and fragmentation. Each plant buds off new ones, so a few soon cover the surface. Pieces that break off keep growing, so pulling a clump apart spreads it.

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