Rheum lobatum Litv. ex Losinsk.
Rheum plicatum Losinsk.
Rheum vvedenskyi Sumnev.
Rheum macrocarpum is a herbaceous perennial plant growing from a stout, woody, rhizomatous rootstock; it produces a basal clump of leaves up to 40cm long and 80cm wide on stout petioles that are up to 25cm long; the plant flowers in late spring, producing stout, branched flowering stems[
The plant is harvested from the wild for local use as a source of tannins.
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[
C. Asia - Kirgizstan, Tadzhikistan, Uzbekistan
Wheat fields and slopes[
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Rheum macrocarpum 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[
The roots are a good source of tannins[
]. Tannins can be used as a dyestuff, as a mordant and to preserve natural fibre items such as ropes[