Rumex cardiocarpus Pamp.
Rumex crispus japonicus (Houtt.) Kitam.
Rumex hadroocarpus Rech.f.
Rumex regelii F.Schmidt
Rumex japonicus is a herbaceous perennial plant growing from a taproot. The erect stems can be 50 - 100cm tall[
The plant is harvested from the wil for local use as a food and dye. The young shoots are sold in local food markets in Korea[
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[
E. Asia - Russian Far East, China, Japan, Korea.
Wet meadows and ditches in lowland all over Japan[
]. Field margins, streambanks and wet valleys; at elevations from sea level to 3,400 metres[
Species in this genus generally succeed in a variety of soils, but they prefer deep fertile moderately heavy soils that are humus-rich, moisture-retentive and also well-drained, with a position in full-sun or part shade[
Being wind -pollinated, Rumex species usually hybridize readily, especially with other members of the genus they are more closely related to[
Leaves - cooked[
]. They can be used as a vegetable or added to soups[
]. The young shoots are harvested in the spring[
]. The leaves can also be dried for later use[
Seed - cooked[
]. It is used with rice or ground into a powder for making dumplings[
The plant is used medicinally[
]. No further information is given, though it is likely that the plant's astringency (especially of the root) is particularly valued[
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[
Seed - sow spring in situ.
Division in spring.