Rheum officinale aka Tibetan Rhubarb

Rheum officinale is a perennial in the knotweed family, Polygonaceae. Its common names include Chinese rhubarb and medicinal rhubarb. It comes from central China, reaching southwest Henan. Plants For A Future also lists several western Chinese provinces. It grows on hills and beneath forest trees. Its recorded habitat spans elevations of 3,937–13,123 feet [1,200–4,000 metres]. This is a plant of temperate climates.

In cultivation, plants reach about 6.6 feet [2 metres] tall. Their spread reaches about 4.9 feet [1.5 metres]. This size gives them a place in broad garden beds. They can also provide ground cover in woodland gardens. For this use, space plants about 5.9 feet [1.8 metres] apart. Flowers appear from June to July. Each flower has both male and female organs. Wind carries the pollen, and seeds ripen from July to August.

Choose sun or partial shade and deep, fertile soil. Add humus where needed to help the soil hold moisture. The roots need moist ground that still drains well. Loam and heavy clay both suit this species. It accepts mildly acid, neutral, and mildly alkaline soils. Plants For A Future reports cold tolerance near −4°F [−20°C]. It lists USDA zones 6–9. Plants have grown well in a shaded woodland garden. Those planted close to trees did less well. It can also grow among coarse grass cut in autumn.

Chinese growers cultivate this species as a medicinal plant. Its roots have a history of use in Chinese medicine. They contain anthraquinones, tannins, and bitter compounds. The first group can have a strong laxative effect. These uses do not make it a routine food crop. Plants For A Future gives it a low food rating. It records leaf stalks as edible raw or cooked. The same source describes their taste as medicinal. Its leaf warning draws on the genus, not confirmed species evidence. That warning concerns oxalic acid and risks for some people.

Raise new plants from seed or divide established rootstocks. Sow seed in a cold frame in autumn or spring. Give seedlings protection through their first winter before planting out. Divide plants in early spring or autumn. Keep at least one growth bud on each piece. Grow small divisions under protection until they establish. Plants For A Future records no weed potential for this species.