Spirodela polyrrhiza - Great Duckweed

Family:	Lemnaceae
Habit:	Perennial
Height:	0.01
Width:	0.05
Synonyms:	Lemna polyrhiza
Range:	Europe, including Britain, south and east from Scandanavia to N. Africa and Asia. America, Australia

Spirodela polyrrhiza (Great Duckweed) is a Perennial which grows to a height of 0.01m and a width of 0.05m . It has a fast growth rate. It has a hardness rating of 5.
Great Duckweed will flower in January. The flowers from this plant are monoecious (both sexes are found on the plant but each flower is either male or female) and they are pollinated by

Soil Information

Great Duckweed will grow in light (sandy),medium (loamy),hard (clay) soil. It is not necessary for the soil to be well drained.
The soil prefers the following PH / acid levels :
- pH of less than 6, Acidic soils
- pH between 6 and 8, Neutral soils
- pH greater than 8, Basic soils
Great Duckweed prefers soils

Ideal Planting Locations

Great Duckweed should not be planted in shady areas.

Still water in ditches and ponds[17].

Planting places suited to this plant described below.

• Is a pond plant

Cultivation Details

Requires a sunny position in still water that is rich in nitrates and lime[200]. A very small plant without differentiation into various parts such as leaf, stem etc (they are called Thalli), it is 8mm in diameter and often forming a mat on the water surface and perennating by means of buds (turions) that sink in autumn and rise to the surface in spring. The so-called rootcap (really only an apical swelling), has a higher specific gravity than any other part of the plant, righting capsized individuals[200].

Edible Uses*

* See disclaimer
Edible Rating: 1/5
The plant is sometimes used as a food[177, 183]. No more details are given.

• Leaves -

Medicinal Uses*

* See disclaimer
Medicinal Rating: 2/5
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].

• Antipruritic - Treats itching of the skin.
• Antipyretic - Treats fevers. See Febrifuge.
• Cardiotonic - A tonic for the heart.
• Carminative - Reduces flatulence and expels gas from the intestines.
• Diaphoretic - Induces perspiration.
• Diuretic - Acts on the kidneys, promoting the flow of urine.

Propagation

The plant divides freely in the growing season and does not need help.

Known Hazards

None known

Other Uses

None known

Cultivars

no recorded cultivars

References

Flora of the British Isles.
Clapham, Tootin and Warburg.
Author: Clapham, Tootin and Warburg.
Rating:
Publisher : A very comprehensive flora, the standard reference book but it has no pictures.
Date of Publication : 1962

The New RHS Dictionary of Gardening. 1992.
Huxley. A.
Author: Huxley. A.
Rating:
Publisher : Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
Date of Publication : 1992

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