Polygonum lapathifolium

Curlytop Knotweed

PolygonaceaeLeavesSeeds/NutsPotential hazards — see below

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Yiching Lin

What to Eat

Edible parts: Leaves, Seed

Young leaves - raw or 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

Temperate regions of the northern hemisphere, including Britain. S. Africa.

TEMPERATE ASIA: Afghanistan, Cyprus, Iran, Iraq, Israel, Lebanon, Syria, Turkey, Russian Federation-Ciscaucasia (Ciscaucasia), Armenia, Azerbaijan, Georgia, Russian Federation (Dagestan), Russian Federation-Western Siberia (Western Siberia), Russian Federation-Eastern Siberia (Eastern Siberia), Kazakhstan, Tajikistan, Turkmenistan, Uzbekistan, Mongolia, Russian Federation-Far East (Far East), China (Anhui Sheng, Fujian Sheng, Gansu Sheng, Guangdong Sheng, Guangxi Zhuangzu Zizhiqu, Guizhou Sheng, Hainan Sheng, Hebei Sheng, Heilongjiang Sheng, Henan Sheng, Hubei Sheng, Hunan Sheng, Jiangsu Sheng, Jiangxi Sheng, Jilin Sheng, Liaoning Sheng, Nei Mongol Zizhiqu, Ningxia Huizi Zizhiqu, Qinghai Sheng, Shaanxi Sheng, Shandong Sheng, Shanxi Sheng, Sichuan Sheng, Xinjiang Uygur Zizhiqu, Yunnan Sheng, Zhejiang Sheng), Korea, Japan, Taiwan TROPICAL ASIA: Bhutan, India, Nepal, Pakistan, Myanmar, Thailand, Vietnam, Indonesia EUROPE: Denmark, United Kingdom, Ireland, Norway, Sweden, Austria, Belgium, Switzerland, Czech Republic, Germany, Hungary, Netherlands, Poland, Slovakia, Russian Federation (European part), Belarus, Estonia, Lithuania, Latvia, Moldova, Ukraine (incl. Krym), Albania, Bulgaria, Bosnia and Herzegovina, Greece, Croatia, Italy (incl. Sardinia, Sicily), North Macedonia, Montenegro, Romania, Serbia, Slovenia, Spain (incl. Baleares), France (incl. Corsica), Portugal AFRICA: Spain (Canarias), Portugal (Madeira Islands), Algeria (north), Egypt, Morocco, Tunisia

How to Identify

Polygonum lapathifolium is a ANNUAL growing to 0.8 m (2ft 7in). See above for USDA hardiness. It is hardy to UK zone 5. 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 moist or wet soil.

How to Grow

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.

Medicinal Uses

Antiseptic Astringent Febrifuge Stomachic. The whole plant is antiseptic and astringent. An infusion has been used in the treatment of stomach complaints and fevers. The plant produces a soft white mass, a froth like that of soap. It is applied externally to burns.