Least Duckweed, Spotless watermeal
Wolffia arrhiza
Family: Lemnaceae
What it is like
Wolffia arrhiza is an evergreen Perennial. See above for USDA hardiness. It is hardy to UK zone 7. It is in leaf all year, in flower all year, and the seeds ripen all year. The species is hermaphrodite (has both male and female organs). Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: neutral and basic (mildly alkaline) soils and can grow in very alkaline soils. It cannot grow in the shade. It can grow in water.
Height (m): 0
Where it is found
Floating on quiet waters. A rare native of southern Britain, growing in still waters.
Europe, including Britain, to Asia.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 4
Leaves - cooked. An excellent flavour, they taste somewhat like a sweet cabbage. The leaves are very nutritious, containing about 20% protein, 44% carbohydrate. 5% fat and are rich in vitamins A, B2, B6, C and nicotinic acid.
Medicine
Rating: 0
Other
Rating:
How it is grown
A pond plant, floating on the surface of the water, it requires a sunny position in still water that is rich in nitrates and lime. At the limit of its climatic range in Britain and probably best grown in a cold water aquarium. It over-winters in temperate areas by means of resting buds which sink to the bottom of the pond in the late autumn and rise again in the spring. One of the smallest flowering plants in the world, it is cultivated as a vegetable in Burma, Laos and Thailand. It has been recommended for commercial cultivation, especially in tropical areas, because of its rapid multiplication and high nutritional value. Plant densities of over two million plants per square metre have been found.
Propagating it: Seed - we have no information on this species but, since it can spread rapidly by division, it really needs no extra help once it is in a pond.
Best place to grow: Pond;
Habit: Perennial
Hardiness: 6-9
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: No shade
Moisture: Water