Common Name:

General Information

Polygonum thunbergii is a prickly, erect to ascending annual plant that can grow around 30 - 90cm tall[]
The plant is harvested from the wild for local use as a food. It has been shown to have excellent potential for use as a hyperaccumulator, being grown in soils polluted with heavy metals in order to remove them.

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[].

Botanical References

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Range

E. Asia - Russian Far East, eastern China, Japan, Korea, northeast India, Vietnam, Thailand.

Habitat

Wet grassy places in lowland and mountains all over Japan[]. Wet valleys, grassy slopes; at elevations from 100 - 2,400 metres[].

Properties

Edibility Rating
Other Uses Rating
Habit	Annual
Height	0.70 m
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Species in this genus generally succeed in an ordinary garden soil, whilst preferring a moisture retentive not too fertile soil in sun or part shade[]. They generally rpays generous treatment[].
Most plants in this genus seem to be immune to the predations of rabbits[].

Edible Uses

Young plant - cooked[, ].

We have no specific information for this species, but the seed of most, if not all, members of the genus is edible both raw and cooked, and is potentially a good source of amino acids. Unfortunately the seed is also usually rather small and fiddly to utilize[].

Medicinal

None known

Agroforestry Uses:

The plant has been shown to have excellent potentional as a bio-accumulator to take up heavy metals from polluted soils. It is especially effective in removing copper and zinc[]. The plants are grown in the polluted soil then removed, thus removing some of the metals, The plants are burnt to ash - the metals can be recovered from the ash, or the ash buried in a safe site[].

Other Uses

None known

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.