Spirodela polyrhiza (Giant Duckweed)
Size: 1+ cm frond width
Position and Usage: Floating plant
Growth rate: Fast
Lighting: 2/5 – 5/5
Water Conditions: 15 – 30°C; pH of 6.0 – 8.0
CO2: Not required
Propagation: Asexual budding; sexual reproduction through seeds
Spirodela polyrhiza is native to the ponds, lakes, bayous, and sluggish streams of Florida. ‘Giant Duckweed’, largest of the Duckweed species, is an easily-cultivated plant that will grow in most temperate and tropical climates. Its flat, oval leaves can reach up to 1 cm in diameter and will float on the surface of a tank, grouped together in dense colonies that may house both micro- and macro-invertebrates, as well as provide shelter for small fish. The leaves are green with a red underside.
S. polyrhiza is hardy and requires neither high intensity lighting nor CO2 supplementation. It can tolerate a range of tank conditions but will thrive in nitrate, phosphate, and potassium-rich water. Hobbyists should note that healthy plants will propagate quickly and can blanket the surface of a tank when left unsupervised, depleting both light and oxygen availability, although the large size of this duckweed allows for easy control. Colonies may be removed as necessary but should be disposed of properly to avoid waterway contamination.