T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Lemna minor (Duckweed)

Kingdom: Plantae
(Unranked): Angiosperms
(Unranked): Monocots
Order: Alismatales
Family: Araceae
Subfamily: Lemnoideae
Tribe: Lemneae
Genus: Lemna
Species: L. minor
Binomial name: Lemna minor
Common names: Common Duckweed, NZ Chickweed, Lesser Duckweed

Lemna minoris a species of Lemna (duckweed) with a subcosmopolitan distribution, native throughout most of Africa, Asia, Europe and North America, occurring everywhere that freshwater ponds and slow-moving streams occur, except for arctic and subarctic climates.
Duckweed is a small free-floating plant that can cover the surface of wind-protected fertile waters. It is a native species and widespread throughout New Zealand. It has one, two or three leaves each with a single root hanging in the water; as more leaves grow, the plants divide and become separate individuals. The root is 1-2 cm long. The leaves are oval, 1-8 mm long and 0.6-5 mm broad, light green, with three (rarely five) veins, and small air spaces to assist flotation. It propagates mainly by division, and flowers are rarely produced; when produced, they are about 1 mm diameter, with a cup-shaped membranous scale containing a single ovule and two stamens. The seed is 1 mm long, ribbed with 8-15 ribs.
It forms colonies water with high nutrient levels and a pH of between 5 and 9, optimally between 6.5 and 7.5, and temperatures between 6 and 33 °C. Growth of colonies is rapid, and the plant frequently forms a complete carpet across still pools when conditions are suitable. In temperate regions, when temperatures drop below 6 to 7 °C it develops small, dense, starch-filled organs called 'turions', which become dormant and sink to the water bottom for winter; the following spring, these recommence growth and float back to the surface.

It is an important food resource for many fish and birds (notably ducks); it is rich in protein and fats, Birds are also important in dispersing the species to new sites; the root is sticky, enabling the plant to adhere to the plumage or feet while the bird flies from one pond to another. Because of its rapid growth rate it may be considered a pest. Around the world it is also grown as a commercial crop for animal feed, primarily for fish and poultry, as it is fast-growing and easy to harvest by surface skimming.