Rheum × hybridum
Rheum × collinianum Baill.
Rheum × cultorum Thorsrud & Reisaeter
Rheum × dentatum Mart.
Common Name: Rhubarb
Rheum × hybridum is a herbaceous perennial plant growing from a stout, woody, rhizomatous rootstock; it produces a basal clump of leaves up to on stout petioles that are up to 50cm long; the plant flowers in the summer, producing flowering stems up to 150cm tall[
Rhubarb is a cultivated food crop in the temperate zone, often being grown on a commercial basis.
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[
This species is of hybrid origen, bred as a food crop, and is not known as truly wild.
Steppe, sparse woods and sandy soils[
Plants are very cold hardy, tolerating temperatures down to at least -20°c[
]. The plant does not like hot summers, however, and is likely to die in warmer climates[
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[
]. It succeeds in most soils provided the drainage is good[
] and will grow in the dappled shade of trees so long as there is sufficient side light[
]. It grows well in heavy clay soils. Tolerates acid conditions but prefers a pH in the range 6.5 to 7[
Rhubarb is a long-lived and almost indestructible perennial plant[
]. It is often cultivated for its edible leaf stems, there are many named varieties[
This species is probably of hybrid origin, Rheum rhaponticum x Rheum rhabarbarun[
]. It hybridizes freely with other members of the genus[
Most cultivars produce edible stems from spring to early summer, though a few, such as '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.
Plants in this genus seem to be immune to the predations of rabbits[
Leaf stem - raw or cooked[
]. An acid taste, it is used as a fruit substitute in spring, usually stewed with sugar and used in pies, jams etc[
]. The juice strained from stewed rhubarb can add colour and flavour to a fruit punch[
]. 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[
The roots of many members of this genus are used medicinally. Whilst Rheum 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[
]. It has a safe and gentle action, safe even for children to use[
]. The plant is also part of a North American formula called essiac which is a popular treatment for cancer. Its effectiveness has never been reliably proven or disproven since controlled studies have not been carried out. The other herbs included in the formula are Arctium lappa, Ulmus rubra and Rumex acetosella[
The root is anticholesterolemic, antiseptic, antispasmodic, antitumor, aperient, astringent, cholagogue, demulcent, diuretic, laxative, purgative, stomachic and tonic[
]. The roots contain anthraquinones, which have a purgative effect, and also tannins and bitters, which have an opposite astringent effect[
]. When taken in small doses, it acts as an astringent tonic to the digestive system, whilst larger doses act as a mild laxative[
]. The root is taken internally in the treatment of chronic constipation, diarrhoea, liver and gall bladder complaints, haemorrhoids, menstrual problems and skin eruptions due to an accumulation of toxins[
]. This remedy is not prescribed for pregnant or lactating women, nor for patients with intestinal obstruction[
]. Externally, the root is used in the treatment of burns[
]. The roots are harvested in October from plants that are at least six years old, they are then dried for later use[
A homeopathic remedy is prepared from the dried root[
]. This is used especially in the treatment of diarrhoea in teething children[
The leaves can be simmered in hot water to make an insecticide.
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.