Rhubarb (Rheum x cultorum)

At a glance

Lifecycle: Perennial (hardy)
Exposure: Full sun
Frost limit: −40 °C

Cultivation

A very easily grown plant, tolerant of considerable neglect, it prefers a deep, fertile, moderately heavy, humus rich, moisture retentive, well-drained soil in sun or semi-shade. Plants are very cold hardy, tolerating temperatures down to at least -20°c. Rhubarb is a long-lived and almost indestructible perennial plant. Most cultivars produce edible stems from spring to early summer, though 'Glaskin's Perpetual' can be harvested throughout the summer. By digging up the roots in the autumn and exposing them to frost, earlier growth will be initiated. These roots can then be transferred to a cold frame or other protected area where they will produce their edible stems in late winter. It is also possible to produce earlier crops outdoors by covering the plants with a layer of straw and an upturned bucket. This species is probably of hybrid origin, R. rhaponticum x R. palmatum. Plants in this genus seem to be immune to the predations of rabbits.

Propagation

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. This species is a hybrid and will not necessarily breed true to type from seed. However, this does give the opportunity to look for superior plants from amongst the seedlings. 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.

Edible uses

Leaf stem - raw or cooked. It is best not to eat large quantities of the stems because of their oxalic acid content - see the notes above on toxicity. Immature flowers - cooked and used like cauliflower. One report says that the plant contains 0.7% rutin. It does not specify which part of the plant, though it is likely to be the leaves[K].

Medicinal uses

The roots of many members of this genus are used medicinally. Whilst R. palmatum is the main species used in China, we have a report that this species (which has probably been derived from it through cultivation) is used in Korea. The uses of R. palmatum are as follows:- Chinese rhubarb, called Da Huang in China, has a long and proven history of herbal usage, its main effect being a positive and balancing effect upon the whole digestive system. It is one of the most widely used herbs in Chinese medicine. The root is anticholesterolemic, antiseptic, antispasmodic, antitumor, aperient, astringent, cholagogue, demulcent, diuretic, laxative, purgative, stomachic and tonic. A homeopathic remedy is prepared from the dried root.

Material uses

The leaves can be simmered in hot water to make an insecticide.

Habitat

Steppe, sparse woods and sandy soils.

Native range

E. Asia - Siberia.