Japanese knotweed facts

Japanese knotweed also known as Japanese bamboo is not a bamboo but is a member of the family Polygonaceae (Buckwheat family). As its steams have the appearance of bamboo, it is associated with bamboo. It is believed that it got introduced in US from Asia as an ornamental plant and is now considered as noxious plant in many states. It grows wild in the disturbed soils such as ditches, railway tracks, roadsides and near drainage. It is also referred as Mexican bamboo due to its large and hollow stems. It bears small greenish to white flowers that grows in the linear clusters.

Name Japanese knotweed
Scientific Name Fallopia japonica
Native Native to Eastern Asia. It is also available in the Europe, British Isles, USA, Canada, New Zealand and Newfoundland.
Common/English Name Fleece Flower, Monkeyweed, Himalayan Fleece Vine, Hancock’s Curse, Tiger Stick, Pea Shooters, Elephant Ears, Sally Rhubarb, Donkey Rhubarb, American Bamboo, Japanese Bamboo, Mexican Bamboo, Huzhang or Japanese Polygonum
Name in Other Languages French: renouée du Japon
China: huzhang
Czech Republic: kridlatka japonska
Denmark: Japansk-pileurt
Estonia: vooljas kirburohi
Finland: Japanintatar
Germany: Japan-knöterich
Ireland: glúineach bhiorach
Japan: itadori
Netherlands: duizendknoop
New Zealand: Asiatic knotweed
Poland: rdest ostrokonczysty
Sweden: parkslide
UK: donkey rhubarb
USA: elephant-ear bamboo
Plant Growth Habit Vigorous, herbaceous shrub
Soil Well drained
Plant Size 1-3 m (3-10 ft)
Lifespan Perennial
Rhizomes (Root system) Dark brown, with interior bright orange
Stem Hollow, smooth, purple-green; Diameter: 2.5cm (1”)
Leaf Alternate, oval-triangular, Length: 10-17 cm, Width: 7-10 cm
Flowering Season July- September
Flower Small, white to green, Length: 1/6-1/8 inch
Shoots Fleshy, red tinged
Shoots shape & size Across: 30 cm x 30 cm
Achenes Dark brown, glossy; Length: 2-4 mm, Width: 2 mm
Fruit Winged, shiny, triangular, small;  Length: 1/10 inch
Health Benefits
  • Cognitive problems
  • Heart ailments
  • Lowers blood pressure
  • Gastrointestinal health
  • Prevent cancer
  • Controls insulin
Traditional uses
  • In Japan and China, it is used in traditional medicine to treat health ailments such as hyperlipemia, schistosomiasis, dermatitis, gonorrhoea and athlete’s foot.
  • It is used to prevent stress ulcers and gastric secretion.
  • The roots are used as laxative in traditional Japanese and Chinese herbal medicines.
  • The underground part is used to treat cough, Lyme disease, chronic bronchitis, joint pain, jaundice, hypertension and amenorrhea.
  • The root may interact with blood thinners.
  • One should consult the physician before using Japanese Knotweed to treat health ailments.
  • The tincture made from Japanese Knotweed should not be used by pregnant, lactating women and people with estrogen sensitive cancers.
  • Some caution should be taken while using this Japanese Knotweed because it contains oxalic acid which may worsen the conditions such as rheumatism, hyper-acidity, gout, arthritis or kidney stones.
  • It contains tannins, emodin and phenolic compounds which is toxic.
  • The excessive use may leads to gastrointestinal reactions such as dry mouth, nausea, mouth pain, abdominal pain, vomiting, diarrhea, etc.
How to Eat
  • Young stems are consumed as spring vegetable.
  • In Japan, it is consumed as wild foraged vegetable or sansai.
  • Young leaves and shoots are also consumed as vegetable.
  • The root is used to make cold drinks as a substitute of tea.
  • The sap is used as dye rice noodles which provide a sour flavor.
  • Japanese Knotweed is also used in alcoholic drinks.
  • It could be steamed.
Other Facts
  • It was introduced in the 1800s to the Britain by Victorians as an ornamental plant.
  • In UK, it is considered illegal to plant or grow this specied in wild but could be grown simply in the garden or own land.
  • The natural enemies keep it on control in Japan.
  • The organizers of London’s 2012 Olympics spent about four years to control this weed.
  • In Japan, it is used in traditional medicine and known as itadori which means take away pain.
  • It can cause serious damage.
  • Insects help in the pollination of Japanese knotweed.
  • In USA, the flowers are used as a nectar source to manufacture honey.











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