Polygonum chayuum A.J.Li & B.J.Bao
Rheum altaicum Losinsk.
Rheum nutans Pall.
Rheum orientale Losinsk.
Rheum compactum is a herbaceous perennial plant growing from a stout, woody, rhizomatous rootstock; it produces a basal clump of leaves up to 20 - 30cm in diameter on stout petioles that are up to 25cm long; the plant flowers in the summer, producing flowering stems around 50 - 100cm tall[
The plant is harvested from the wild for local use as a food.
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[
E. Asia - western China (Xinjiang), Kazakhstan, Mongolia, western Siberia to Russian Far East.
Banks of rivers and brooks, valleys and slopes[
]. Slopes; at elevations around 2,000 metres[
Rheum compactum is a moderately cold-hardy plant, tolerating winter temperatures that can fall to about -20°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 in this genus seem to be immune to the predations of rabbits[
Hybridizes freely with other members of this genus[
Leaf stem - cooked[
]. A tart flavour, it can be used as a rhubarb substitute[
The rootstock contains anthocyanins[
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.