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Polygonum amphibium - L.

Common Name Willow Grass, Water knotweed, Longroot smartweed, Water smartweed
Family Polygonaceae
USDA hardiness 4-8
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 Lakes, ponds, slow-flowing rivers and canals, also on banks by the river[17, 187].
Range Most of Europe, including Britain, temperate Asia, N. America and S. Africa.
Edibility Rating    (1 of 5)
Other Uses    (1 of 5)
Weed Potential Yes
Medicinal Rating    (2 of 5)
Care (info)
Fully Hardy Wet Soil Water Plants Semi-shade Full sun
Polygonum amphibium Willow Grass, Water knotweed, Longroot smartweed,  Water smartweed


http://commons.wikimedia.org/wiki/File:Persicaria_amphibia_Sturm62.jpg
Polygonum amphibium Willow Grass, Water knotweed, Longroot smartweed,  Water smartweed
http://commons.wikimedia.org/wiki/User:Pethan

 

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Summary


Physical Characteristics

 icon of manicon of flower
Polygonum amphibium is a PERENNIAL growing to 0.3 m (1ft).
See above for USDA hardiness. It is hardy to UK zone 5. It is in flower from July to September. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers wet soil and can grow in water.

UK Hardiness Map US Hardiness Map

Synonyms

Persicaria amphibia.

Habitats

 Pond; Bog Garden;

Edible Uses

Edible Parts: Leaves  Seed  Shoots
Edible Uses:

Leaves - raw or cooked. The young shoots are eaten in the spring[257]. Seed - cooked[178]. It is rather small and fiddly to utilize.

References   More on Edible Uses

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.
Astringent  Depurative  Pectoral  Poultice  Skin

The whole plant, but especially the root, is astringent, depurative, skin[145, 172, 178, 207]. An infusion of the leaves and stems has been used to treat stomach pains and children with diarrhoea[257]. The root has been eaten raw, or an infusion of the dried, pounded roots used, in the treatment of chest colds[257]. A poultice of the fresh roots has been applied directly to the mouth to treat blisters[257].

References   More on Medicinal Uses

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Other Uses

Tannin

Tannin is obtained from the plant[145]. No more details, but it is likely to be from the root.

Special Uses

References   More on Other Uses

Cultivation details

A water or marsh plant growing in water up to 3 metres deep or in boggy soil[187]. This species is hardy to about -25°c[187]. Plants seem to be immune to the predations of rabbits[233]. The leaves are often attacked by the larvae of the water-lily beetle[187]. Plants can either be aquatic with floating ovate-oblong leaf-blades or a leggy marsh plant with lanceolate leaves[187]. Their stems root at the nodes wherever they come into contact with the soil[200].

References   Carbon Farming Information and Carbon Sequestration Information

Temperature Converter

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Propagation

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.

Other Names

If available other names are mentioned here

Native Plant Search

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Found In

Countries where the plant has been found are listed here if the information is available

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 NameHabitHeightHardinessGrowthSoilShadeMoistureEdibleMedicinalOther
Polygonum alaskanumAlaska Wild RhubarbPerennial1.8 -  LMHSNM21 
Polygonum alpinumAlpine Knotweed, Alaska wild rhubarbPerennial1.0 4-8  LMHSNM21 
Polygonum arenastrumSmall-Leaved Knotweed, Oval-leaf knotweedAnnual0.3 4-8  LMHSNM231
Polygonum aviculareKnotweed, Prostrate knotweedAnnual0.3 4-8  LMHSNM231
Polygonum barbatumJoint WeedPerennial0.8 -  LMHSNM11 
Polygonum bistortaBistort, Meadow bistort, SnakeweedPerennial0.5 4-7 FLMHSNMWe332
Polygonum bistortoidesAmerican BistortPerennial0.5 4-8  LMHSNM31 
Polygonum bungeanumBunge's smartweedAnnual0.8 0-0  LMHSNM10 
Polygonum coccineumWater SmartweedPerennial0.5 4-8  LMHSNWeWa10 
Polygonum conspicuum Perennial0.6 -  LMHSNM10 
Polygonum convolvulusBlack BindweedAnnual1.2 0-0  LMHSNM100
Polygonum divaricatum Perennial1.0 -  LMHSNDM10 
Polygonum douglasiiKnotweed, Douglas' knotweed, Austin knotweed, Engelmann's knotweed, Johnston's knotweed, Large knoAnnual0.3 0-0  LMHSNDM20 
Polygonum dumetorumClimbing false buckwheatAnnual1.8 0-0  LMHSNM11 
Polygonum equisetiforme Perennial1.0 7-10  LMHNDM102
Polygonum fugax Perennial0.0 -  LMHSNM30 
Polygonum hydropiperSmartweed, Marshpepper knotweedAnnual0.8 0-0  LMHNWeWa221
Polygonum japonicumJapanese Knotweed, Mexican Bamboo, Japanese KnotweedPerennial3.0 4-10 FLMHSNM333
Polygonum lapathifoliumCurlytop KnotweedAnnual0.8 4-8  LMHSNMWe111
Polygonum limosum Perennial1.8 -  LMHSNM10 
Polygonum longisetumOriental lady's thumbAnnual0.5 0-0  LMHSNMWe10 
Polygonum maackianum Annual0.8 -  LMHSNMWe10 
Polygonum manshurienseAsian BistortPerennial0.8 -  LMHSNMwe01 
Polygonum microcephalum Perennial0.5 -  LMHSNM10 
Polygonum minusPygmy smartweedAnnual0.3 0-0  LMHSNMWe10 
Polygonum molle Perennial2.5 6-9 FLMHSNM212
Polygonum multiflorumHe Shou Wu, Tuber fleeceflowerPerennial Climber4.5 6-9  LMHSNM23 
Polygonum nepalenseNepalese smartweedAnnual0.3 0-0  LMHSNMWe111
Polygonum orientalePrince's Feather, Kiss me over the garden gateAnnual1.5 0-0  LMHSNM220
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Growth: S = slow M = medium F = fast. Soil: L = light (sandy) M = medium H = heavy (clay). pH: A = acid N = neutral B = basic (alkaline). Shade: F = full shade S = semi-shade N = no shade. Moisture: D = dry M = Moist We = wet Wa = water.

 

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Botanical References

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Subject : Polygonum amphibium  
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