• Latin name
• Family
• Common name(s)
• Synonym(s)
• Geographical distribution
• Morphology
• Biology and ecology
• Agricultural importance
• Management
• Selected references
• Contributors

Pistia stratiotes

Pistia stratiotes (right) leaves form a rosette and are smaller than Salvinia molesta (left) (IRRI).

Latin name

Pistia stratiotes L.

Family

Araceae

Common name(s)

Water lettuce, tropical duckweed

Synonym(s)

Pistia aethiopica Fenzl ex Klotzsch, P. africana Presl C., P. commutata Schleiden, P. crispata Blume, P. occidentalis Blume, P. minor Blume 

Geographical distribution

Asia: China (including Hong Kong).

South and Southeast Asia: Bangladesh, India, Indonesia, Cambodia, Lao PDR, Malaysia, Nepal, Philippines, Sri Lanka, Thailand, and Vietnam.

Rest of the world: Angola, Argentina, Colombia, Congo-Kinshasa, Benin, Burkina Faso, Egypt, Ethiopia, Ghana, Guinea, Honduras, Kenya, Madagascar, Mali, Mauritania, Mozambique, Nicaragua, Niger, Nigeria, Puerto Rico, Senegal, South Africa, Sri Lanka, Sudan, Tanzania, United States (including Hawaii), Uruguay, Venezuela, Zambia, and Zimbabwe.

Morphology

A stemless, floating, aquatic, freshwater stoloniferous perennial herb.

Leaf: few to many in a rosette, 2.5—15—cm—long, obovate to wedge-shaped, erect, truncate and somewhat hairy, and together forming a cup-like plant; basal parts thickened by a porous tissue.

Inflorescence: few white spathes, about 12—mm—long, oblique and shortly peduncled at center of leaf cluster.

Fruit: few to many seeds, irregularly rupturing berry.

Biology and ecology

Growing in stagnant or slowly running fresh water and in lowland rice, canals, ponds, lakes, and rivers.

It propagates vegetatively by offshoots and also by seeds. A plant can produce up to 12 seeds but also 130 offshoots within 2 months. Seeds germinate underwater and seedlings begin to float only when the collar leaf has expanded and when the primary leaf becomes exposed.

Agricultural importance

Pistia stratiotes is a problem in lowland rice fields not only due to competition with rice but also due to difficulty in removing this weed during land preparation as the plants are difficult to bury in mud and may need to be removed manually. The weed also blocks streams and irrigation and navigation canals.

Often cultivated in ponds as a good haven for fish.

Management

Cultural control: removal by hand in rice paddies and in irrigation canals is an effective means of control. Wire screens can also be used to collect the weed before rice planting.

Chemical control: two-week-old P. stratiotes plants reported to be controlled by diquat, glyphosate, and mixtures of piperophos and dimethametryn. 

Selected references

Bua-ngam T, Mercado BL. 1975. The life cycle of water lettuce (Pistia stratiotes L.). Philipp. Weed Sci. Bull. 2:11-15.

Bua-ngam T, Mercado BL. 1977. Response of Pistia stratiotes L. to selective and non-selective herbicides. Philipp. Weed Sci. Bull. 4:1-6.

Holm L, Pancho JV, Herberger JP, Plucknett DL. 1979. A geographical atlas of world weeds. New York (USA): John Wiley & Sons, Inc. 391 p.

Moody K. 1989. Weeds reported in South and Southeast Asia. Manila (Philippines): International Rice Research Institute. 442 p.

Pablico PP, Moody K. 1986. A dry season lowland rice (Oryza sativa) weed survey in Central and Southern Luzon, Philippines. Philipp. J. Weed Sci. 13:39-49.

Pancho JV, Soerjani M.1978. Aquatic weeds of Southeast Asia: a systematic account of common Southeast Asian aquatic weeds. Bogor (Indonesia): SEAMEO Regional Center for Tropical Biology. 130 p.

Soerjani M, Kostermans AJGH, Tjitrosoepomo G. 1987. Weeds of rice in Indonesia. Jakarta (Indonesia): Balai Pustaka. 716 p.

Pistia stratiotes L. Global Compendium of Weeds home page (www.hear.org/gwc/html/index.html).

Plant profile for Pistia stratiotes L. in Plants Database (http://plants.usda.gov).

Contributors

JLA Catindig, RT Lubigan, and DE Johnson