RHUBARB, Rheum, a genus of plants of the natural order polygonar, closely allied to r umex (dock and sorrel), front which it differs in having nine stamens, throe sldeld like and it three-winged achenium. The species, which are numerous. are In r herbaceous plants, natives of the central regions of Asia. with branching, almost 11-shy roots; erect; thick, branching stems, sometimes 6 or 8 ft. high; the stems and brunches while in the bud covered with large membranous sheaths. The leaves are large, sulked, entire, or lobed; the flowers are small, whitish or red, generally very numerous, in large loose panicles of many-flowered clusters. The roots are medicinal; but those of different species seem to possess their medicinal properties in very different degrees. or these properties ire developed very variously in different soils and climates, or according to other circumstances not at all understood. It is not known what species of rhubarb yields She valued rhubarb of commerce, which conies from inland parts of Mina or Chinese Tartary. Some of it reaches Europe by way of Canton. but the best is brought through Russia. It is commonly known, however, is Britain its Turkey rhu barb, because it wns formerly brought by way of .Nntolia. It is carefully examined at Kiaehta by persons appointed by the Russian gaeiiment, so that the superior quality of all that is permitted to enter the Europenn market is secured. Rhubarb is sometimes cultivated for its root in Europe, but the produce, French thabarb and English rhubarb, is very inferior to the rhubarb of the east, which it is often employed to adulterate. About 12 acres are devoted to the cultivation of rhubarb for its root near Banbury. in England, 11w r•pecies cultivated being rheum rheponticum ; but in France, besides tins species, R. a whiled?' in owl R. compactem are employed. At Banbury the roots are taken up when three or four years old, and dried in drying-houses by a carefully regulated heat.
The leaf-stalks of rhubarb contain an agreeable mixture of citric and malic acids, and when young and tender ore much used, like apples, for tarts or pies, and also for making a kind of preserve. For these purposes different kinds of rhubarb are now very exten
sively cultivated in Britain, and in other temperate and cold countries, although it is only since the beginning of the present century that this valuable addition has been made to the plants of our kitchen-gardens; the species previously introduced having been cultivated merely as objects of curiosity, or for the sake of their roots. A number of species have been introduced into cultivation for their leaf-stalks. R. palmetem, the first species known, and which was Once believed to yield the Turkey rhubarb, has roundish green leaf-stalks and half-palmate leaves, with pinnatifid pointed lobes. Its stalks ore very inferior to every other kind in our gardens, both in size and quality, and the appearance of the leaf is very different. The other cultivated kinds, R. undutatanz, R. rhe pouttcum, and R. hybridum, with endless varieties produced by the art of the gar dener. all have broad, heart-shaped, undivided leaves, and the leaf-stalks flattened and grooved on the upper side. The leaf stalks are often also of a reddish color, which in some of the finest varieties pervades their whole flesh. Rhubarb is propagated by seed, and the plants yield a crop in the second or third year, or by dividing the roots. It pre fers a light rich soil; and the ground ought to be heavily manured every year. The pants are placed three or-four feet apart, according to the size of the variety. The varieties which, by excessive manuring, are made to produce the most gigantic stalks, are not nearly so good in quality as the smaller kinds. Rhubarb is cultivated on it most extensive scale by market-gardeners. It is forced in winter and early spring by being placed in pots within houses, or by having pots inverted over it, and dung and straw heaped around; and forced rhubarb is more tender and delicate than that which grows in open air.