Greater Duckweed care guide
Greater Duckweed (Spirodela polyrhiza) — medium light, 18-28 °C, pH 6-8, no CO2.
Compiled by Aquairi from published sources · Published · Updated
Overview
Greater Duckweed (Spirodela polyrhiza) is an aquatic plant of the family Araceae, listed in the Aquairi knowledge base as a beginner-level species. It is typically grown under medium light and without obligatory CO2 injection on any substrate. Larger relative of common duckweed with multiple roots per frond and reddish underside. Excellent shade and nutrient export plant; can dominate a surface quickly.
Taxonomy
- Family: Araceae
- Genus: Spirodela
- Scientific name: Spirodela polyrhiza
- Common synonyms: Giant Duckweed
Habitat
Spirodela is a genus of free-floating plants (Araceae, duckweed subfamily) of still fresh waters worldwide; its rounded fronds are larger than Lemna and bear several roots each. In the Aquairi knowledge base, populations associated with this form are recorded from Cosmopolitan.
Growth requirements
- Lighting: medium
- CO2: not required
- Temperature: 18-28 °C (64-82 °F)
- pH: 6-8
- GH: 3-16 °dGH
- Substrate: any
- Maximum height: 3 cm
- Growth rate: fast
- Recommended placement: floating
Placement
A floating plant that forms a surface layer, providing shade and absorbing excess nutrients from the water column. In the Aquairi knowledge base this form is recommended for the floating layer under medium light and without obligatory CO2 injection, using any substrate.
Propagation
Reproduces by budding, with daughter fronds separating from the parent; it can also form dormant turions that overwinter on the bottom. Documented propagation techniques for this entry include: adventitious plantlets on flower stalks.
Common issues
Rapid surface coverage shades plants below and impedes gas exchange; surplus growth must be skimmed off regularly.
Propagating Greater Duckweed (Spirodela polyrhiza)
Overview
Spirodela polyrhiza, the greater duckweed, is a floating plant whose smooth round flat fronds are 0.5 to 1.0 cm wide. Each frond carries several minute roots and a dark red underside, with the upper surface mostly green. It forms dense colonies that mat across freshwater surfaces and is valued for shade and nutrient export.
Propagation Method
Greater duckweed reproduces vegetatively through frond budding during spring and summer; flowering is rare. New daughter fronds form on and separate from parent fronds. For overwintering it also produces turions, dense dormant buds storing more than 60% starch, which sink and later germinate when water warms.
Step-by-Step
- Skim a small group of healthy multi-rooted fronds from an established mat.
- Float them on still freshwater so the roots dangle freely below.
- Provide medium light and a little dissolved nutrient; parent fronds bud new daughters within days.
- Let the colony spread, then divide off a portion of fronds to seed new containers.
- If turions form and sink, they will germinate on their own once water reaches about 15 C.
Conditions for Healthy Growth
- Temperature 18-28 C; turions germinate near 15 C as water warms.
- Medium surface lighting.
- Calm, still freshwater for a stable mat.
- Low nutrient demand; excels at taking up excess nutrients.
- No CO2 supplementation required.
Maintenance
Thin the mat roughly weekly by netting out excess fronds so light reaches submerged plants and the colony stays in its vegetative growth phase. In cooler conditions expect a natural dormancy as turions sink in fall and regrowth resumes in spring.