Common Name: Smartweed

General Information

Persicaria hydropiper is an erect, annual plant with much-branched stems that form roots at the lower nodes. It can grow 40 - 70cm tall[, ].
The plant is harvested from the wild for local use as a food ad medicine. It is cultivated for its edible leaves in Japan[], where the variety 'Fastigiatum' (syn Persicaria maximowiczii) is the form normally used[, ].

Known Hazards

The gland-dotted leaves are used as a fish poison[].
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[].

Botanical References

,

Range

Widespread through many parts of Europe, the Mediterranean, temperate and tropical Asia to Australia.

Habitat

Shallow water in ponds, ditches etc and in wet places on land[, ]. Riverbanks, streamsides, wet valleys; at elevations from sea level to 3,500 metres in China[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	0.50 m
Pollinators	Self
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Persicaria hydropiper is a very widespread plant, found growing from the cold temperate zone to the tropics. Two subspecies are sometimes distinguished - subsp. hydropiper is found in temperate climates, all parts are larger and the fruits are mostly 2-sided, whilst subsp. microcarpa (Danser) Soják is found in tropical climates, all parts are smaller and the fruits are usually 3-sided[].
A water plant, growing in shallow water or wet soils. Succeeds in most soils if they are wet and dislikes shade.
Plants seem to be immune to the predations of rabbits[].

Edible Uses

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

Seed - raw or cooked. It is rather small and fiddly to utilize. The seed is used as a condiment - a pepper substitute[].
The sprouted seeds or young seedlings can be used as a garnish or added to salads, they are commonly sold in Japanese markets[]. They are very hot[, ].

Medicinal

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[, , , , ]. They contain rutin, which helps strengthen fragile capillaries and thus helps prevent bleeding[]. Use with caution[].
The bruised leaves are used as a poultice and as a remedy for toothache[].

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[, ]. A poultice of the plant is used in treating swollen and inflamed areas[].
In Chinese tests, the plant was ranked 20th in a survey of 250 potential antifertility drugs[].

The seed is carminative, diuretic and stimulant[].

The root is bitter, stimulant and tonic[].

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

Other Uses

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

Propagation

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.