Rhubarb (Lat. rha, or rheu barbarum, a name given by the early writers), in medicine, the root" alone of rheum officinale and some other species, but in horticulture the name of the plants of several species. The genus rheum (either from Gr. , to flow, in reference to its purgative properties, or from Rha, the ancient name of the Volga, upon the banks of which it grew) belongs to Asia and southern Russia; and growing in localities from which Europeans have been excluded, there has been much confusion as to the species, of which according to Meisner there are about 20. They are all perennials, with large woody rootstocks, from which proceed radical leaves with long, thick petioles, the blade of the leaf usually very broad, entire, or variously lobed, and with strong palmate ribs; the annual stem is erect, large, and hollow, bearing smaller leaves, and spikes or panicles of flowers; all the leaves have large sheathing stipules, but those of the stem leaves are very conspicuous; the apeta-lous flowers have a white, greenish or pinkish, six-parted calyx; nine stamens; a triangular ovary, surmounted by three styles, and becoming a three-winged fruit. The common rhubarb of the gardens, or pie plant, as it is frequently called, is a familiar representative of the genus; this species, R. Rhaponticum (with several synonymes), a native of Siberia and the country along the Volga, was introduced into England as early as 1573, and in the time of Elizabeth its leaves were in use as a pot herb, like spinach.
It is now cultivated in gardens solely for its acid petioles or leaf stalks, which are used as a substitute for fruit, a custom un-known until early in the present century. Com-ing early in spring (and they may be had by forcing at any time during the winter), at a season when fruit is scarce, the leaf stalks are in great demand; their consumption in England is even more general than with us. The rapidly grown stalks contain but little woody fibre, and cook readily to a pulp, which with sugar is used for pies, tarts, and other culinary preparations; their acidity is due in part to oxalic, but more largely to malic acid, both acids being in combination with potash as acid salts; it disagrees with some, but its large consumption indicates that it is not especially deleterious. About 1860 great efforts were made to establish its Use as a wine plant, but the product proved inferior, and was by many considered injurious. There are several garden varieties, as at one time many seedlings were raised with a view to produce plants with the greatest development of leaf stalk; the Cahoon has stalks 3 in. or more in diameter and often 2 ft. long, but it is coarse and harsh in flavor; the best variety is Myatt's Linnaeus, very early, of medium size, tender, and of excellent flavor; Tobolsk is a small kind, very early and good.
For field culture the plants are raised in a seed bed, and when a year old are transplanted to 3 or 4 ft. each way; they yield the third year; small plantings are made by dividing the old roots into as many pieces as they have buds, and setting out the pieces; the soil can hardly be too rich. Rhubarb is readily forced by placing the plants in winter in boxes or barrels with earth in a warm cellar, or on a larger scale in frames. In the present style of subtropical gardening the rhubarbs are employed on account of their vigor of growth and picturesqueness; an isolated plant of the common rhubarb is very effective, but the Nepaul rhubarb (R. Emodi) is much finer; the leaves are a yard across, and have red veins; this is cultivated in England by gardeners for the sake of its large leaves, which are used for covering baskets of fruit. The finest of all the species is the Himalayan (R. nobile), discovered by Dr. J. D. Hooker; it forms a pyramid a yard and more high, the base of which is of shining green leaves with red petioles and nerves, and the upper parts of delicate straw-colored bracts with pink edges. - Rhubarb as a drug has been known from very early times, and it is said to be treated of in a Chinese herbal written about 2700 B. C. European naturalists early endeavored to ascertain the exact species that produced the excellent kinds of rhubarb procured through Russia and Turkey, and distinguished by the name of either one of these countries.
Several species of rheum have from time to time been regarded as furnishing the better sorts; it is probably produced by different species, one of which is R. officinale; this is much larger than the garden rhubarb, differing among other characters in having nearly cylindrical petioles, and the under side of the leaf being covered with short, erect hairs. Formerly the best variety was known as Turkey rhubarb, being brought by caravans from Tartary by way of Persia to the Levant ports, whence it reached Europe; but rhubarb from this source disappeared from the trade about a quarter of a century ago. A similar article entered commerce by way of Russia, and was known as Russian rhubarb. It was brought to the frontier town of Kiakhta, where it was rigorously inspected by the agent of the Russian government. Every piece of the root was perforated to the centre in order to prove its soundness, and all the defective pieces were destroyed; those accepted were sent to St. Petersburg. The roots were of irregular shape, and appear to have been sliced on the surface with knives, probably for removing the bark, and marked with the large holes going partly through which were made for inspection.
On account of the superior quality of the Russian rhubarb it commanded a high price, and to secure this other varieties were made to imitate it. The opening of various ports in northern China, and the rebellion beginning in 1851, exerted a depressing influence on the trade at Kiakhta, and, the Chinese being very willing to avoid the great severity of the Russian inspection, the quantity of rhubarb delivered there became so small that the rhubarb office was abolished in 1863, so that Russian rhubarb has become a thing of the past. Most of the rhubarb that comes to the United States is from China, shipped from Canton. Some of this is very good, though still inferior to the Russian. The roots are more cylindrical and smoother, as if scraped; they are not of so bright a color, and the powder has a reddish brown tinge. Defective pieces are mixed in with the best, and as all are usually powdered together the medicine must be of inferior efficacy. The Chinese sometimes attempt to give it the appearance of the Russian variety by cutting it into angular shapes, and filling up with powdered root, in order to conceal the little holes that have been made through the roots for suspending them on strings to dry.
It is believed that both the Russian and Chinese come from the same regions in Chinese Tartary and China proper, but there being in the Chinese market no such stringent regulations about the preparation of the drug, the inferior qualities are sent there. The roots are allowed to grow six years before they are sufficiently mature; and after they are dug the bark is removed and the root cut in pieces for drying, which is done in the sun and by the aid of fire heat. Owing to the risk and expense of land transport, rhubarb was in ancient times considerably more costly than opium. It is now purchased for the European market chiefly at Hankow on the upper Yang-tse. From 1866 to 1872 the average exports of rhubarb from Hankow were over 3,000 peculs (1 pecul = 133 1/2 lbs.). The cultivation of rhubarb for its root has been attempted in various European countries, and was at one time carried on by order of the Russian government in southern Siberia; some is produced in Hungary, Moravia, and Silesia; in France the cultivation, which in former years was considerable, has ceased except in the neighborhood of Avignon and in a few other localities.
In England the cultivation of rhubarb for commerce commenced about a century ago, and is still continued, the product being known in our commerce; it was formerly called Crimean rhubarb, and is sometimes fraudulently sold as the Turkey drug; in England it is known as Banbury rhubarb, from the locality of the plantations. The root is simply pared, sliced, and dried in a kiln; though very handsome in appearance, English rhubarb is of very inferior character. The species is mainly the common garden rhubarb (E. Rhaponticum). The medicinal qualities of the root are much affected by soil and climate, and those species known to give a valuable drug in their native localities yield in the cooler and moister climate of Europe a much deteriorated product. The rhubarb as imported, while hardly subject to adulteration, varies greatly in quality, unsound and poor being mixed with the good, and the inferior pieces being covered with a yellow powder to conceal the surface. In the powdered state there is, as with other drugs, ample room for adulteration, and a large share of that sold is of inferior quality. - The taste of rhubarb is a bitter astringent, the smell aromatic, though to most persons disagreeable; when chewed it crackles in the teeth from the presence of minute crystals of oxalate of lime, and it imparts a yellow color to the saliva.
The best sorts are recognized by the bright yellow color of the powder. Its chemical composition is very complicated, and chemists have failed to discover any peculiar principle in the drug which fully accounts for its purgative properties. Brandos found in 100 parts of Chinese rhubarb 2 of pure rhubarbaric acid, 7.5 of the same impure, 2.5 of gallic acid, 9 of tannin, 3.5 of coloring extractive, 11 of uncrystallizable sugar with tannin, 4 of starch, 14.4 of gummy extractive, 4 of pectic acid, 1.1 of malate and gallate of lime, 11 of oxalate of lime, 1.5 of sulphate of potassa and chloride of potassium, 1 of silica, 0.5 of phosphate of lime and oxide of iron, 25 of lignine, and 2 of water. The analyses of Schlossberger and Döpping are still more elaborate, introducing a variety of new principles, among which the chrysophanic acid, resembling the rhubarbaric acid of Bran-des, is the most interesting. It is a beautiful yellow substance, emitting yellow vapors when heated, soluble in alcohol, its alkaline solution of a fine red color, and those with potassa changing by evaporation to a violet and then to blue. It is a purgative, but less powerful than rhubarb itself.
Magnificent purples also are obtained from the yellow coloring matter produced by treating rhubarb with nitric acid and then with alkalies; and it has been proposed to apply these, called erythose, in the arts as a dyestuff. The still more recent examinations of Kubly (1867) do not materially change the aspect of the question. - The medical properties of rhubarb are very peculiar. Its first effects upon the system are cathartic, and to these succeeds an astringent action, checking the excessive operation of the purgative. The medicine is at the same time tonic and stomachic. As a purgative its action is moderate, and affects rather the muscular fibre than the secretory vessels. Its use is obviously indicated for relaxed conditions of the bowels, when the stomach is enfeebled, and a gentle cathartic is required, as in certain cases of dyspepsia, diarrhoea, dysentery, etc. It is much used in combination with magnesia, calomel, and other cathartics, when greater purgative action is required. This action may be reduced by roasting or long boiling.
It is exhibited in powder, sometimes made into pills with soap, also in infusion, sirup, and tincture.
Himalayan Rhubarb (Rheum nobile).
Medicinal Rhubarb (Rheum officinale).