Oriental lady's thumb
Polygonum longisetum

Family: Polygonaceae

What it is like

Polygonum longisetum is a ANNUAL growing to 0.5 m (1ft 8in). It is in flower from May to June, and the seeds ripen from June to August. 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 or wet soil.

Height (m): 0.5

Where it is found

Wet grassy sunny places in lowland all over Japan. Moist valleys, along streambanks, shaded places along ditches and water sides from sea level to 3100 metres in China.

E. Asia - China, Japan, Korea.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 1

Young leaves - raw or cooked. A famine food, used when all else fails. Seed - raw or cooked. It is rather small and fiddly to utilize.

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 0

Other

Rating:

How it is grown

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 should succeed outdoors in most 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. Succeeds in wet soils. Repays generous treatment. Plants seem to be immune to the predations of rabbits.

Propagating it: 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.

Best place to grow: Bog Garden;

Habit: Annual

Hardiness: 0-0

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist, wet

Things to keep in mind

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.

Its other names

Local names

Synonyms

Persicaria longiseta. (De Bruyn.)Kitag.