Lemna gibba aka Fat Duckweed

Lemna gibba, or fat duckweed, belongs to the arum family, Araceae. Its native range spans Europe, central Asia, and northwestern India. It also includes Africa and the Americas. The RHS lists it as native to Britain and Ireland. This water plant grows in temperate regions. It lives in still, nutrient-rich water, including ponds with mild winters.

The plant spreads across water rather than forming an upright clump. Plants For A Future lists a height of 0.66 feet [0.2 metres]. Its spread varies, so that source gives no fixed width. Growth is fast, and division lets it spread without help. Sources differ on its life cycle. Kew classes it as an aquatic annual; Plants For A Future calls it perennial. The latter describes resting buds that sink in late autumn. They rise again in spring after spending winter underwater.

Plants For A Future reports separate male and female flowers on each plant. It can flower in Britain in a warm, sheltered, sunny spot. That source places Britain near the edge of its climate range. No flowering months are given in the supplied evidence. For cultivation, choose still water with plenty of nitrates and lime. It needs sun and does not grow in shade. Neutral to mildly alkaline conditions suit it. Plants For A Future lists USDA hardiness zones 4–11.

Ponds and water containers offer places to grow this duckweed. Fish and birds can feed on the growing plants. Its growth also gives pond creatures cover. Yet its fast spread can make it a nuisance in ponds. Scoop out excess growth to keep it in check. The removed plants can go on the compost heap. Division is so rapid that established plants need no help to multiply. Its pond value therefore comes with a need to watch its spread.

Plants For A Future lists the leaves as edible, raw or cooked. It reports cultivation in Israel for salads and use as a vegetable. The same source records no known hazards. That statement does not establish safety for every person or pet. It lists no known medicinal uses. The supplied evidence gives no named pests or diseases for this species.