Polygonum tinctorium

Aiton.

PolygonaceaeLeavesSeeds/NutsPotential hazards — see below

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Royal Botanic Gardens, Kew

What to Eat

Edible parts: Leaves, Seed

Young plant - cooked. Seed - raw or cooked. It is rather small and fiddly to utilize.

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.

Where to Find It

E. Europe to E. Asia.

TEMPERATE ASIA: China (Guangdong Sheng, Guangxi Zhuangzu Zizhiqu, Hebei Sheng, Hubei Sheng, Jiangsu Sheng, Liaoning Sheng, Shaanxi Sheng, Shandong Sheng, Shanxi Sheng, Sichuan Sheng)

How to Identify

Polygonum tinctorium is a ANNUAL growing to 0.8 m (2ft 6in). It is frost tender. It is in flower from July to August, and the seeds ripen from September to November. 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 cannot grow in the shade. It prefers moist soil.

How to Grow

Succeeds in an ordinary garden soil but prefers a moisture retentive not too fertile soil in sun or part shade. Requires full sun and a fertile soil. Prefers hot humid climates. A frost tender plant, it can be grown as a half-hardy annual in Britain. This plant used to be cultivated as a dye plant. Plants seem to be immune to the predations of rabbits.

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.

Medicinal Uses

Antidote Antiinflammatory Antiphlogistic Antipyretic Depurative Febrifuge. The stems and the leaves are antidote, anti-inflammatory, antiphlogistic, antipyretic and depurative. Their use increases the phagocytosis of white blood cells and decreases the permeability of the capillaries. The indigo pigment in the leaves is used. It is used in the treatment of freckles, pimples, erysipelas, mumps, thrush, epidemic protitis, infantile convulsions and high febrile conditions of children. The leaves and fruits are used in Korea to help protect the liver and to treat burns and food poisoning caused by eating fish. The fruits are antidote and febrifuge. The plant is anti-inflammatory.