This taxon has a history of name change. It was first published by Nakai in 1908 as Polygonum japonicum var conspicuum in Bot. Mag. (Tokyo) 22: (63) (1908). Nakai then renamed it a year later as Polygonum conspicuum in Bot. Mag. (Tokyo) 23: (389) (1909). In 1926, Nakai again moved it, this time to Persicaria conspicua in Bot. Mag. (Tokyo) 40: 51 (1926). In 2006, it was moved once more, by Koji Yonekura, to Persicaria macrantha subsp. conspicua in Fl. Japan 2a: 164 (2006). Further information has now shown that this taxon is actually a subspecies of Persicaria odorata and, in 2012, Koji Yonekura renamed this taxon as Persicaria odorata subsp. conspicua in The Journal of Japanese Botany 87: 151-168.
Polygonum odoratum is a popular food, spice and medicinal plant in parts of southeast Asia, where the spicy leaves are a valued part of many dishes. Subspecies conspicua also has edible leaves, but varies from the main species in having odourless leaves, and so, presumably, much less flavour.

Common Name:

General Information

Polygonum conspicuum is a perennial plant growing from a rhizomatous rootstock; it produces a clump of erect stems 50 - 100cm tall[].
The plant is harvested from the wild for local use as a food.

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 - east and southern China, Japan, Korea.

Habitat

Wet sunny places in lowland, C. and S. Japan[]. Streamsides and riverbanks; at elevations from sea level to 1,500 metres in eastern China[].

Properties

Edibility Rating
Habit	Perennial
Height	0.60 m
Self-fertile	No
Cultivation Status	Wild

Cultivation Details

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[].
Dioecious, male and female plants must be grown if seed is required.

Edible Uses

Leaves - raw or 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

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.
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.