Common Name: Da Huang

General Information

Rheum tanguticum is a herbaceous perennial plant growing from a stout, woody, rhizomatous rootstock; it produces a basal clump of leaves around 30 - 60cm in diameter on stout petioles that are up to 50cm long; the plant flowers in the summer, producing flowering stems around 150 - 200cm tall[].
The plant is harvested from the wild for local use as a food and medicine. It is one of several species of Rheum used in Japan for medicinal purposes and is included in the Japanese Pharmacopoeia[],

Known Hazards

The plant, but especially the leaf blades, contains several toxic compounds, particularly anthraquinone glycosides, but also soluble oxalates and calcium oxylate crystals[, , ]. At lower doses these can cause abdominal cramps, burning of the mouth and throat, headache, weakness, nausea and vomiting. In larger, quantities it can lead to coma and death, though generally very large quantities need to be eaten for the plant to be fatal.
The leaf stems (petioles) have much lower quantities of toxins and, in several Rheum species are a commonly eaten food. The main caution here are the levels of oxalates. These can lock up certain minerals (especially calcium) in the body, leading to nutritional deficiency. Cooking the plant will reduce the concentration 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

,

Range

E. Asia - western and central China (Tibet, Qinghai, Gansu).

Habitat

Valleys, at elevations from 1,600 - 3,000 metres[].

Properties

Edibility Rating
Medicinal Rating
Habit	Perennial
Height	2.00 m
Pollinators	Wind
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Rheum tanguticum is a moderately cold-hardy plant, tolerating winter temperatures that can fall to about -15°c[].
Rheum species generally prefer a deep, fertile, moderately heavy, humus rich, moisture retentive, well-drained soil in sun or semi-shade[]. They grow well along the woodland edge or amongst large shrubs[]. They succeed in heavy clay soils. Plants can be grown in quite coarse grass, which can be cut annually in the autumn[].
Hybridizes freely with other members of this genus[].
This species is favoured for its medicinal properties over Rheum palmatum[] and is cultivated as a medicinal plant in China[].
Plants in this genus seem to be immune to the predations of rabbits[].
Hybridizes freely with other members of this genus[].

Edible Uses

Leaf stem - raw or cooked[, , , ]. The stem is superior in flavour to the common rhubarb and quite tender[]. An acid flavour, it is sometimes used as a cooked fruit substitute[].

Medicinal

Rhubarb has a long and proven history of herbal usage, its main effect being a positive and balancing effect upon the whole digestive system. It is one of the most widely used herbs in Chinese medicine[].
The root is anticholesterolemic, antiseptic, antispasmodic, antitumor, aperient, astringent, cholagogue, demulcent, diuretic, laxative, purgative, stomachic and tonic[, , , , , , , ]. The roots contain anthraquinones, which have a purgative effect, and also tannins and bitters, which have an opposite astringent effect[]. When taken in small doses, it acts as an astringent tonic to the digestive system, whilst larger doses act as a mild laxative[, ]. The root is taken internally in the treatment of chronic constipation, diarrhoea, liver and gall bladder complaints, haemorrhoids, menstrual problems and skin eruptions due to an accumulation of toxins[]. This remedy is not prescribed for pregnant or lactating women, nor for patients with intestinal obstruction[]. Externally, the root is used in the treatment of burns[]. The roots are harvested in October from plants that are at least six years old, they are then dried for later use[].
A homeopathic remedy is prepared from the dried root[]. This is used especially in the treatment of diarrhoea in teething children[].

Other Uses

None known

Propagation

Seed - best sown in autumn in a shaded cold frame[]. The seed can also be sown in spring in a cold frame. When large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse or cold frame for their first winter, planting them out in the spring.
Division in early spring or autumn[, ]. Divide up the rootstock with a sharp spade or knife, making sure that there is at least one growth bud on each division. 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.