Rheum compactum aka Thick Leaved Rhubarb

Rheum compactum is a perennial in the knotweed family, Polygonaceae. The RHS calls it thick-leaved rhubarb. Its native range runs from Central Asia to Russia’s Far East. Records include Mongolia, eastern Kazakhstan, northern Xinjiang, and parts of Russia. It grows in temperate regions and is not native to Britain or Ireland. Wild plants grow beside rivers and streams, in valleys, and on slopes. PFAF also records it on Tibetan slopes around 6,560 feet [2,000 metres] above sea level.

PFAF gives its height as about 1.6 feet [0.5 metres]. This makes it a low-growing plant by that account. The supplied sources give no mature spread or detailed leaf description. It flowers from July to August. Each flower has both male and female organs, and wind carries the pollen. Seeds ripen from August to September, following the summer bloom.

In gardens, it suits cultivated beds with deep, fertile soil. It prefers soil rich in humus that holds moisture but drains well. Loam and heavier clay both suit it. PFAF reports that it grows well even in heavy clay. It accepts mildly acid, neutral, and mildly alkaline soils. Choose a site in sun or partial shade. Keep the soil moist rather than choosing a dry site. PFAF lists USDA zones 5–9 and cold tolerance near −4°F [−20°C].

Grow new plants from seed or by dividing the rootstock. Sow seed in a shaded cold frame in autumn. Spring sowing in a cold frame is another option. Move seedlings into separate pots once large enough to handle. Keep them under cover through their first winter, then plant out in spring. Divide established plants in early spring or autumn. Each piece needs at least one growth bud. Large divisions can go straight into their final sites. Grow smaller pieces in pots until they establish well.

The cooked leaf stalks have a sour taste. PFAF lists them as a substitute for rhubarb. This edible use concerns the stalks, not the leaf blades. Its safety note gives no confirmed hazard specific to this species. Instead, it raises a broader warning about oxalic acid in rhubarb leaves. That warning does not establish this species’ toxicity. PFAF lists no known medicinal or other uses. The supplied evidence gives no species-specific pest or disease problems.