Rumex japonicus
Family: Polygonaceae
What it is like
Rumex japonicus is a PERENNIAL growing to 1 m (3ft 3in). It is in flower from May to June, and the seeds ripen from June to July. The species is hermaphrodite (has both male and female organs) and is pollinated by Wind. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. 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.
Height (m): 1
Where it is found
Wet meadows and ditches in lowland all over Japan. Field margins, streambanks and wet valleys from sea level to 3400 metres in China.
E. Asia - China, Japan, Korea.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 2
Leaves - cooked. They can be used as a vegetable or added to soups. The leaves can also be dried for later use. Seed - cooked. It is used with rice or ground into a powder for making dumplings.
Seed: includes nuts, cereals, peas and beans.
Medicine
Rating: 0
Other
Rating: 1
Although no specific mention has been made for this species, dark green to brown and dark grey dyes can be obtained from the roots of many species in this genus, They do not need a mordant.
Dye: Plants that provide dyes.
How it is grown
We have very little information on this species and do not know if it will be hardy in Britain, though judging by its native range it should succeed outdoors in most parts of this country. The following notes are based on the general needs of the genus. Succeeds in most soils but prefers a deep fertile moderately heavy soil that is humus-rich, moisture-retentive but well-drained and a position in full-sun or part shade.
Propagating it: Seed - sow spring in situ. Division in spring.
Best place to grow: Bog Garden;
Habit: Perennial
Hardiness:
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Moist
Things to keep in mind
Plants can contain quite high levels of oxalic acid, which is what gives the leaves of many members of this genus an acid-lemon flavour. Perfectly alright in small quantities, the leaves should not be eaten in large amounts since the oxalic acid can lock-up other nutrients in the food, especially calcium, thus causing mineral deficiencies. The oxalic acid content will be reduced if the plant is cooked. 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.