Polygonum barbatum

Joint Weed

PolygonaceaeLeavesShootsPotential hazards — see below

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Yiching Lin

What to Eat

Edible parts: Leaves, Shoots

Tender young leaves and shoots - cooked as a vegetable. They have a somewhat pungent flavour.

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. Asia - Himalayas to western and southern China

TEMPERATE ASIA: China (Fujian Sheng, Guangdong Sheng, Guangxi Zhuangzu Zizhiqu, Guizhou Sheng, Hainan Sheng, Hubei Sheng, Hunan Sheng, Jiangxi Sheng, Sichuan Sheng, Yunnan Sheng), Japan (Ryukyu Islands), Taiwan TROPICAL ASIA: Bhutan, India, Sri Lanka, Nepal, New Guinea, Myanmar, Thailand, Vietnam, Indonesia, Malaysia, Philippines

How to Identify

Polygonum barbatum is a PERENNIAL growing to 0.8 m (2ft 6in). It is in flower from August to September, and the seeds ripen from September to October. The species is hermaphrodite (has both male and female organs). 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 moist soil.

How to Grow

We have very little information on this species and do not know if it is hardy in Britain, though judging by its native range it could succeed outdoors at least in the milder parts of the country. The following notes are based on the general needs of the genus. Succeeds in an ordinary garden soil but prefers a moisture retentive not too fertile soil in sun or part shade. Repays generous treatment. 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. 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.

Medicinal Uses

Astringent Carminative Parasiticide. The seeds are used to relieve the griping pains of colic. The root is astringent and cooling. A paste of the root is used externally in the treatment of scabies.

Other Uses

Parasiticide. None known