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Polygonum hydropiper - L.
Common Name Smartweed, Marshpepper knotweed
Family Polygonaceae
USDA hardiness Coming soon
Known Hazards 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[238].
Habitats Shallow water in ponds, ditches etc and in wet places on land[9, 17].
Range Europe, including Britain, from Norway south and east to N. Africa and temperate Asia.
Edibility Rating  
Other Uses  
Weed Potential No
Medicinal Rating  
Wet Soil Water Plants Full sun


Polygonum hydropiper Smartweed, Marshpepper knotweed

Polygonum hydropiper Smartweed, Marshpepper knotweed
Physical Characteristics
 icon of manicon of flower
Polygonum hydropiper is a ANNUAL growing to 0.8 m (2ft 7in). It is in flower from Jul to September. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Self.The plant is self-fertile.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It prefers wet soil and can grow in water.

P. fastigiatoramosum. Makino. P. maximowiczii. Regel. Persicaria fastigiatoramosa. (Makino.)Nakai. P

 Pond; Bog Garden;
Edible Uses
Edible Parts: Leaves;  Seed.
Edible Uses: Condiment;  Rutin.

Leaves and stems - raw or cooked. They can also be made into an acid peppery condiment[183]. They are very hot[116]. The leaves contain about 7.5% protein, 1.9% fat, 8% carbohydrate, 2% ash[179]. The leaves are said to contain rutin[218]. Seed - raw or cooked. It is rather small and fiddly to utilize. The seed is used as a condiment - a pepper substitute[100]. The sprouted seeds or young seedlings can be used as a garnish or added to salads, they are commonly sold in Japanese markets[183]. They are very hot[116, 179].
Medicinal Uses

Plants For A Future can not take any responsibility for any adverse effects from the use of plants. Always seek advice from a professional before using a plant medicinally.

Antiinflammatory;  Astringent;  Carminative;  Contraceptive;  Diaphoretic;  Diuretic;  Emmenagogue;  Homeopathy;  
Stimulant;  Stomachic;  Styptic.

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[4, 9, 21, 147, 152]. They contain rutin, which helps strengthen fragile capillaries and thus helps prevent bleeding[222]. Use with caution[21]. The seed is carminative, diuretic and stimulant[218]. 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[218, 254]. A poultice of the plant is used in treating swollen and inflamed areas[257]. In Chinese tests, the plant was ranked 20th in a survey of 250 potential antifertility drugs[218]. A homeopathic remedy is made from the leaves[9]. It is used in the treatment of piles, menstrual pains and other menstrual complaints[9].
Other Uses

A yellow-gold dye is obtained from the stalks[106].
Cultivation details
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[116], the variety 'Fastigiatum' (syn P. maximowiczii) is the form normally used[58, 116]. Plants seem to be immune to the predations of rabbits[233].
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.
Other Names
Found In
Weed Potential

Right plant wrong place. We are currently updating this section. Please note that a plant may be invasive in one area but may not in your area so it’s worth checking.

Conservation Status
IUCN Red List of Threatened Plants Status :
Related Plants
Latin NameCommon NameEdibility RatingMedicinal Rating
Polygonum alaskanumAlaska Wild Rhubarb21
Polygonum alpinumAlpine Knotweed, Alaska wild rhubarb21
Polygonum amphibiumWillow Grass, Water knotweed, Longroot smartweed, Water smartweed12
Polygonum arenastrumSmall-Leaved Knotweed, Oval-leaf knotweed23
Polygonum aviculareKnotweed, Prostrate knotweed23
Polygonum barbatumJoint Weed11
Polygonum bistortaBistort, Meadow bistort, Snakeweed33
Polygonum bistortoidesAmerican Bistort31
Polygonum bungeanumBunge's smartweed10
Polygonum coccineumWater Smartweed10
Polygonum conspicuum 10
Polygonum convolvulusBlack Bindweed10
Polygonum divaricatum 10
Polygonum douglasiiKnotweed, Douglas' knotweed, Austin knotweed, Engelmann's knotweed, Johnston's knotweed, Large kno20
Polygonum dumetorumClimbing false buckwheat11
Polygonum equisetiforme 10
Polygonum fugax 30
Polygonum japonicumJapanese Knotweed, Mexican Bamboo, Japanese Knotweed33
Polygonum lapathifoliumCurlytop Knotweed11
Polygonum limosum 10
Polygonum longisetumOriental lady's thumb10
Polygonum maackianum 10
Polygonum manshurienseAsian Bistort01
Polygonum microcephalum 10
Polygonum minusPygmy smartweed10
Polygonum molle 21
Polygonum multiflorumHe Shou Wu, Tuber fleeceflower23
Polygonum nepalenseNepalese smartweed11
Polygonum orientalePrince's Feather, Kiss me over the garden gate22
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Readers comment
Mark R.
These webpages cover a whole range of spices and their known chemical makeup. A very informative source on teh properties of many edible plants. Jun 4 2011 12:00AM
The tastes relates to chemicals called alkamides, these are typically found in planst such as the Szechuan pepper (Zanthoxylum simulans), Sansho Pepper(Zanthoxylum piperatum), Paracress (Acmella oleracea syn. Spilanthes oleracea).
Gernot Katzer's Spice Pages
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Subject : Polygonum hydropiper  

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