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Family Polygonacea
Drooping knotweed
Polygonum pubescens Blume
La liao

Scientific names Common names
Polygonum pubescens Blume Drooping knotweed (Engl.)
Polygonum flaccidum Hook. f.  
Polygonum roettleri Roth.  
Persicaria pubescens (Blume) H. Hara  

Other vernacular names
CHINESE: Fu mao liao, Ban jiao cao, Chui liao, La liao cao, Ruan jing shui liao.
JAPANESE: Bontoku tade.

Polygonum pubescens is a perennial herb, much taller than Polygonum hydropiper, up to 75 centimeters tall. Leaves are stalkless, 5 to 15 centimeters long, smooth or hairy. Pinkish-red flowers are borne in drooping racemes, 15 centimeters long, and slender. Nut is small, black, and minutely granular.

- In swampy places at low altitude in Cagayan Province in Luzon.
- Also occurs in India, China, Taiwan and Malaya.

Emmenagogue, abortifacient.


- Leaves used as potherb or seasoning.
- In China the bruised plant is applied locally to blistered and swollen feet.
- Used for snake bites.
- Also used as emmenagogue and abortifacient.
- In India's Arunachal Pradesh, whole plant paste is thrown into the stream to stupefy the fish, make them float up for an easy catch.

Phytoremediation / Cadmium:
Study evaluated the accumulation characteristics of Cd in Polygonum pubescens. Under all test concentrations, Cd content in the roots and shoots exceeded 100 mg/kg and the enrichment coefficient over 1. Results showed P. pubescens has high tolerance and accumulation capacity of Cd, with a potential on phytoremediation of Cd-contaminated soil. (2)


Last Update June 2013

IMAGE SOURCE: File:Persicaria pubescens.JPG/ Show_ryu / 4 Oct 2010 / GNU Free Documentation License / Wikimedia Commons

Additional Sources and Suggested Readings
Traditional knowledge of Adi tribe of Arunachal Pradesh on plants / R C Srivastava and Adi community / Indian Journ of Traditional Knowledge, Vol 8(2), April 2009, pp 146-153
Accumulation characteristics of Cd in Polygonum pubescens Bl. / Deng Hua / Agricultural Science and Technology (Jun. 2010)

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