The flowers are small, greenish-white to rose-red, and grouped in large compound leafy inflorescences.

The fruits are a three-sided achene with winged sides, and the seeds are albuminous with a straight or curved embryo.

The genus Rheum was erected in 1753 by Carl Linnaeus,[4] initially for three species: R. rhaponticum, R. rhabarbarum and R. ribes.

[11] The 1989 Plants of Central Asia, dealing with a larger geographical remit, has Alisa E. Grabovskaya-Borodina recognising only 12 species, synonymising a great number.

[15] Oxyria Rumex Rheum In the 1998 Flora Republicae popularis Sinicae A. R. Li proposed classifying the Chinese representatives of the genus into five sections.

[16][17] Losinskaja used a slightly different classification in the Flora SSSR in 1936:[11] The genus is represented by about 50–60 extant species.

[20] Rheum species are often the host plants for myrmecophilous caterpillars of the butterfly genus Callophrys; Callophrys titanus feeds on R. maximowiczii in southern Kazakhstan,[21] C. mystaphia on R. ribes in eastern Turkey,[22] and C. mystaphioides on R. persicum in southwest and central Iran.

[24] Beetles which are specialised herbivores of this plant species in eastern Turkey are a Petrocladus sp.

[25] In the Taldy-Bulak valley in the Talas Alatau of Kyrgyzstan, the emerging leaves of R. maximowiczii are an important food source for Himalayan brown bear (Ursus arctos ssp.

The plants also produce other compounds, including citric acid and anthraquinone glycosides, and the raw or cooked leaf blades are poisonous to humans and livestock if consumed in large enough amounts.

Some species are grown for their ornamental qualities, including R. acuminatum, R. alexandrae, R. australe, R. kialense, R. palmatum, R. rhabarbarum and R.