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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


Young leaves and plants - raw or cooked[2][3]. Used as a potherb[4], they are very rich in zinc[5]. A nutritional analysis is available[6].

Seed - raw or cooked. Rather small and fiddly to utilize, they can be used in all the ways that buckwheat (Fagopyrum esculentum) is used, either whole or dried and ground into a powder for use in pancakes, biscuits and piñole[7][8][9][10][4].

The leaves are a tea substitute[4].
There are no edible uses listed for Polygonum arenastrum.

Material uses

Yields a blue dye that is not much inferior to indigo[11]. The part used is not specified, but it is likely to be the leaves.

Yellow and green dyes are obtained from the whole plant[12].

The roots contain tannins, but the quantity was not given[13].
There are no material uses listed for Polygonum arenastrum.

Medicinal uses(Warning!)

Knotweed is a safe and effective astringent and diuretic herb that is used mainly in the treatment of complaints such as dysentery and haemorrhoids. It is also taken in the treatment of pulmonary complaints because the silicic acid it contains strengthens connective tissue in the lungs[14].

The whole plant is anthelmintic, astringent, cardiotonic, cholagogue, diuretic, febrifuge, haemostatic, lithontripic and vulnerary[7][15][16][17][18][19][20][21][22]. It was formerly widely used as an astringent both internally and externally in the treatment of wounds, bleeding, piles and diarrhoea[7]. Its diuretic properties make it useful in removing stones[7]. An alcohol-based preparation has been used with success to treat varicose veins of recent origin[15]. The plant is harvested in the summer and early autumn and is dried for later use[16]. The leaves are anthelmintic, diuretic and emollient[6]. The whole plant is anthelmintic, antiphlogistic and diuretic[6]. The juice of the plant is weakly diuretic, expectorant and vasoconstrictor[6]. Applied externally, it is an excellent remedy to stay bleeding of the nose and to treat sores[7]. The seeds are emetic and purgative[7][23].

Recent research has shown that the plant is a useful medicine for bacterial dysentery. Of 108 people with this disease, 104 recovered within 5 days when treated internally with a paste of knotweed[14].
There are no medicinal uses listed for Polygonum arenastrum.


Ecosystem niche/layer

Ecological Functions

Nothing listed.


Nothing listed.


Nothing listed.


Seed - sow spring in a cold frame. 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. Division in spring or autumn. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.

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


Succeeds in an ordinary garden soil[24] but prefers a moisture retentive not too fertile soil in sun or part shade[25]. Repays generous treatment, in good soils the plant will cover an area up to a metre in diameter[24][7]. Prefers an acid soil[26]. Dislikes shade.

Knotweed is a common and invasive weed of cultivated ground[15]. It is an important food plant for the caterpillars of many species of butterflies[27]. It also produces an abundance of seeds and these are a favourite food for many species of birds[7]. Plants seem to be immune to the predations of rabbits[28]. The flowers have little or no scent or honey and are rarely visited by pollinating insects. Self-fertilization is the usual method of reproduction, though cross-fertilization by insects does sometimes occur[7]. The plant also produces cleistogomous flowers - these never open and therefore are always self-fertilized[7].

The plant is very variable according to habitat and is seen by most botanists as part of an aggregate species of 4 very variable species, viz. - P. aviculare. L.; P. boreale. (Lange.)Small.; P. rurivacum. Jord. ex Box.; and P. arenastrum. Bor[29].


Problems, pests & diseases

Associations & Interactions

There are no interactions listed for Polygonum arenastrum. 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 arenastrum.




None listed.


None listed.

Full Data

This table shows all the data stored for this plant.

Binomial name
Polygonum arenastrum
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
light shade
Soil Texture
Soil Water Retention
Environmental Tolerances
  • Strong wind
  • Maritime exposure
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

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  1. ? Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. ISBN 0-7513-020-31 (1995-00-00)
  2. ? 2.02.1 Tanaka. T. Tanaka's Cyclopaedia of Edible Plants of the World. Keigaku Publishing (1976-00-00)
  3. ? 3.03.1 Kunkel. G. Plants for Human Consumption. Koeltz Scientific Books ISBN 3874292169 (1984-00-00)
  4. ? Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications ISBN 0-9628087-0-9 (1990-00-00)
  5. ? 5.05.1 Reid. B. E. Famine Foods of the Chiu-Huang Pen-ts'ao. Taipei. Southern Materials Centre (1977-00-00)
  6. ? Duke. J. A. and Ayensu. E. S. Medicinal Plants of China Reference Publications, Inc. ISBN 0-917256-20-4 (1985-00-00)
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  8. ? 8.08.1 Harris. B. C. Eat the Weeds. Pivot Health (1973-00-00)
  9. ? 9.09.1 Coon. N. The Dictionary of Useful Plants. Rodale Press ISBN 0-87857-090-x (1975-00-00)
  10. ? 10.010.1 Yanovsky. E. Food Plants of the N. American Indians. Publication no. 237. U.S. Depf of Agriculture. ()
  11. ? 11.011.1 Johnson. C. P. The Useful Plants of Great Britain. ()
  12. ? 12.012.1 Grae. I. Nature's Colors - Dyes from Plants. MacMillan Publishing Co. New York. ISBN 0-02-544950-8 (1974-00-00)
  13. ? 13.013.1 Rottsieper. E.H.W. Vegetable Tannins The Forestal Land, Timber and Railways Co. Ltd. (1946-00-00)
  14. ? Chevallier. A. The Encyclopedia of Medicinal Plants Dorling Kindersley. London ISBN 9-780751-303148 (1996-00-00)
  15. ? Chiej. R. Encyclopaedia of Medicinal Plants. MacDonald ISBN 0-356-10541-5 (1984-00-00)
  16. ? Launert. E. Edible and Medicinal Plants. Hamlyn ISBN 0-600-37216-2 (1981-00-00)
  17. ? 17.017.1 Lust. J. The Herb Book. Bantam books ISBN 0-553-23827-2 (1983-00-00)
  18. ? 18.018.1 De. Bray. L. The Wild Garden. ()
  19. ? 19.019.1 ? A Barefoot Doctors Manual. Running Press ISBN 0-914294-92-X ()
  20. ? 20.020.1 Schofield. J. J. Discovering Wild Plants - Alaska, W. Canada and the Northwest. ()
  21. ? 21.021.1 Yeung. Him-Che. Handbook of Chinese Herbs and Formulas. Institute of Chinese Medicine, Los Angeles (1985-00-00)
  22. ? 22.022.1 Stuart. Rev. G. A. Chinese Materia Medica. Taipei. Southern Materials Centre ()
  23. ? 23.023.1 Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement). Council of Scientific and Industrial Research, New Delhi. (1986-00-00)
  24. ? 24.024.1 F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press (1951-00-00)
  25. ? Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press ISBN 0-333-47494-5 (1992-00-00)
  26. ? Riotte. L. Companion Planting for Successful Gardening. Garden Way, Vermont, USA. ISBN 0-88266-064-0 (1978-00-00)
  27. ? Carter D. Butterflies and Moths in Britain and Europe. Pan ISBN 0-330-26642-x (1982-00-00)
  28. ? Thomas. G. S. Perennial Garden Plants J. M. Dent & Sons, London. ISBN 0 460 86048 8 (1990-00-00)
  29. ? 29.029.1 Clapham, Tootin and Warburg. Flora of the British Isles. Cambridge University Press (1962-00-00)

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