Practical ecological knowledge for the temperate reader.

Spirodela polyrhiza - Great duckweed

Family: Lemnaceae [E-flora]

"Spirodela polyrrhiza is a PERENNIAL at a fast rate. It is hardy to zone (UK) 5. It is in flower in July. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant). Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It can grow in water." [PFAF]

"General: Fronds annual, free-floating, round to egg-shaped, (3) 5-10 mm long, purplish beneath, stalked, in single or small groups, 5- to 11-nerved, with 5 to 15 rootlets." [IFBC-E-flora]

"Flowers: Usually 3 per pouch, 2 male, 1 female, enclosed in 2 lateral budding pouches sheathed by a minute membrane." [IFBC-E-flora]

"Habitat / Range Ponds and slow-moving streams in the lowland, steppe and montane zones; frequent in SW and SC BC, infrequent elsewhere except absent on N Vancouver Island, the Queen Charlotte Islands and NW BC; circumpolar, E to PQ and NS and S to FL, MS, TX, NM, AZ, CA and MX; Eurasia, S America." [IFBC-E-flora] "Still water in ditches and ponds[17]. Eutrophic, quiet waters, in temperate to tropical regions[270]. Europe, including Britain, south and east from Scandanavia to N. Africa and Asia. America, Australia" [PFAF]

Status: Native [E-flora]

Food Use

Medicinal Use

"The whole plant is antipruritic, antipyretic, cardiotonic, carminative, diaphoretic, diuretic[147, 176, 218]. It stimulates the appearance of measles rash[147, 176]. It is used in the treatment of colds, measles, oedema and difficulty in urination[176]." [PFAF]



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