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Toxic parts

Although no specific mention has been made for this species, there have been reports that some members of this genus can cause photosensitivity in susceptible people. Many species also contain oxalic acid (the distinctive lemony flavour of sorrel) - whilst not toxic this substance can bind up other minerals making them unavailable to the body and leading to mineral deficiency. Having said that, a number of common foods such as sorrel and rhubarb contain oxalic acid and the leaves of most members of this genus are nutritious and beneficial to eat in moderate quantities. Cooking the leaves will reduce their content of oxalic acid. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition[1].

Edible uses


Leaves and stems - raw or cooked. They can also be made into an acid peppery condiment[2]. They are very hot[3]. The leaves contain about 7.5% protein, 1.9% fat, 8% carbohydrate, 2% ash[4]. The leaves are said to contain rutin[5].

Seed - raw or cooked. It is rather small and fiddly to utilize. The seed is used as a condiment - a pepper substitute[6].

The sprouted seeds or young seedlings can be used as a garnish or added to salads, they are commonly sold in Japanese markets[2]. They are very hot[3][4].

Unknown part


Material uses

A yellow-gold dye is obtained from the stalks[7].

Unknown part


Medicinal uses(Warning!)

Smartweed has a long history of herbal use, both in Eastern and Western herbalism. It is not used very often, and is seen more as a domestic remedy being valued especially for its astringent properties which makes it useful in treating bleeding, skin problems, diarrhoea etc.

The leaves are anti-inflammatory, astringent, carminative, diaphoretic, diuretic, emmenagogue, stimulant, stomachic, styptic[8][9][10][11][12]. They contain rutin, which helps strengthen fragile capillaries and thus helps prevent bleeding[13]. Use with caution[10]. The seed is carminative, diuretic and stimulant[5]. The whole plant, either on its own or mixed with other herbs, is decocted and used in the treatment of a wide range of ailments including diarrhoea, dyspepsia, itching skin, excessive menstrual bleeding and haemorrhoids[5][14]. A poultice of the plant is used in treating swollen and inflamed areas[15]. In Chinese tests, the plant was ranked 20th in a survey of 250 potential antifertility drugs[5].

A homeopathic remedy is made from the leaves[9]. It is used in the treatment of piles, menstrual pains and other menstrual complaints[9].


Ecosystem niche/layer

Ecological Functions

Nothing listed.


Nothing listed.


Nothing listed.


Seed - sow spring in a pot standing in water or in situ. Germination is usually free and easy. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer if they have reached sufficient size. If not, overwinter them in a cold frame and plant them out the following spring after the last expected frosts.

Practical Plants is currently lacking information on propagation instructions of Polygonum hydropiper. Help us fill in the blanks! Edit this page to add your knowledge.


A water plant, growing in shallow water or wet soils. Succeeds in most soils if they are wet and dislikes shade.

Smartweed is cultivated for its edible leaves in Japan[3], the variety 'Fastigiatum' (syn P. maximowiczii) is the form normally used[16][3].

Plants seem to be immune to the predations of rabbits[17].


Problems, pests & diseases

Associations & Interactions

There are no interactions listed for Polygonum hydropiper. Do you know of an interaction that should be listed here? edit this page to add it.

Polycultures & Guilds

There are no polycultures listed which include Polygonum hydropiper.




None listed.


None listed.

Full Data

This table shows all the data stored for this plant.

Binomial name
Polygonum hydropiper
Imported References
Material uses & Functions
Edible uses
None listed.
Material uses
None listed.
Medicinal uses
None listed.
Functions & Nature
Provides forage for
Provides shelter for
Hardiness Zone
Heat Zone
full sun
no shade
Soil PH
Soil Texture
Soil Water Retention
Environmental Tolerances
    Native Climate Zones
    None listed.
    Adapted Climate Zones
    None listed.
    Native Geographical Range
    None listed.
    Native Environment
    None listed.
    Ecosystem Niche
    None listed.
    Root Zone Tendancy
    None listed.
    Deciduous or Evergreen
    Herbaceous or Woody
    Life Cycle
    Growth Rate
    Mature Size
    Flower Colour
    Flower Type


    1. ? Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. ISBN 0-7513-020-31 (1995-00-00)
    2. ? Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications ISBN 0-9628087-0-9 (1990-00-00)
    3. ? Brooklyn Botanic Garden Oriental Herbs and Vegetables, Vol 39 No. 2. Brooklyn Botanic Garden (1986-00-00)
    4. ? Reid. B. E. Famine Foods of the Chiu-Huang Pen-ts'ao. Taipei. Southern Materials Centre (1977-00-00)
    5. ? Duke. J. A. and Ayensu. E. S. Medicinal Plants of China Reference Publications, Inc. ISBN 0-917256-20-4 (1985-00-00)
    6. ? 6.06.1 Polunin. O. Flowers of Europe - A Field Guide. Oxford University Press ISBN 0192176218 (1969-00-00)
    7. ? 7.07.1 Coon. N. The Dictionary of Useful Plants. Rodale Press ISBN 0-87857-090-x (1975-00-00)
    8. ? 8.08.1 Grieve. A Modern Herbal. Penguin ISBN 0-14-046-440-9 (1984-00-00)
    9. ? Launert. E. Edible and Medicinal Plants. Hamlyn ISBN 0-600-37216-2 (1981-00-00)
    10. ? Lust. J. The Herb Book. Bantam books ISBN 0-553-23827-2 (1983-00-00)
    11. ? 11.011.1 ? A Barefoot Doctors Manual. Running Press ISBN 0-914294-92-X ()
    12. ? 12.012.1 Lassak. E. V. and McCarthy. T. Australian Medicinal Plants. ()
    13. ? 13.013.1 Foster. S. & Duke. J. A. A Field Guide to Medicinal Plants. Eastern and Central N. America. Houghton Mifflin Co. ISBN 0395467225 (1990-00-00)
    14. ? 14.014.1 Chevallier. A. The Encyclopedia of Medicinal Plants Dorling Kindersley. London ISBN 9-780751-303148 (1996-00-00)
    15. ? 15.015.1 Moerman. D. Native American Ethnobotany Timber Press. Oregon. ISBN 0-88192-453-9 (1998-00-00)
    16. ? Ohwi. G. Flora of Japan. (English translation) Smithsonian Institution (1965-00-00)
    17. ? Thomas. G. S. Perennial Garden Plants J. M. Dent & Sons, London. ISBN 0 460 86048 8 (1990-00-00)
    18. ? Clapham, Tootin and Warburg. Flora of the British Isles. Cambridge University Press (1962-00-00)