The cultivation of Rheum undulatum and R. rhaponticum has for some time past been carried on profitably at Clamart, near Paris, and the products of both plants, as so cultivated, are confounded in commerce under the name of French rhubarb. Recently, M. Gallais has been making some experiments in the cultivation of Rheum officinale at Ruffec, in the Charente department, and he has communicated his manner of proceeding and results to the Paris Societé d' Acclimatation. ("Bulletin" , vol. vii, p. 667.)
In the selecting of a suitable spot for the experiment, M. Gallais states that he was guided by the following considerations: The Rheum officinale grows in Asia, between the 30th and 39th parallels of latitude, at an elevation of 4,000 feet above the sea level. The isothermal line of 12.9° of temperature passes by Pekin, of which the latitude is 39° 54' 13" N., and above Milan rises to latitude 45° 54', running to the west of Europe. By taking this isothermal line and adding half a degree of temperature for each degree of latitude towards the south, and deducting one degree of temperature for each 172 meters of elevation above the level of the sea, he arrived at the conclusion that in the natural habitat of the plant the average climatic temperature was 19° in summer and zero in winter. Ruffec, the place where M. Gallais' experiment has been carried on, is situated in latitude 46° 11" N., longitude 2° 8' 17" has an average temperature of 17° C. in summer and 1.2°C. in winter, and is at an elevation of 96 meters above the sea level.
According to the analyses of Fremy and Pelouze, the rhubarb plant is rather rich in potash and sulphuric acid, less so in silica, more or less rich in lime, and rich in phosphoric acid. The soil at Ruffec is calcareous, sandy and very nitrogenous, being composed partly of sands proceeding from old degradations. These sands contain a considerable abundance of silicious and aluminous matters. The soil is very permeable, requiring during the summer months about 5 cubic meters of water per acre.
M. Gallais commenced operations with a plant obtained from Dr. Giraudeau, which, in its turn, was derived from the original plant grown in the Botanical garden of the Paris Medical School, from which the species Rheum officinale was described by Professor Planchon in 1872. (See "Pharmaceutical Journal" , vol. iv, p. 690.)
The plant cultivated in the shade, with a northern exposure, and in moist places, developed a luxuriant vegetation, both in the size of its root and the amplitude of the leaves. But the product under such conditions appears to have been of doubtful quality.
Whilst working upon the plant in the spring a very short stem was. noticed, appearing like a ball covered with black scales, from which issued in the first days of March an enormous bud, resembling, both in size and color, a hen's egg. This bud gradually developed and gave off leaves, which in the first year of the plantation attained a diameter of 1 meter.
In the month of June, desiring to develop a vigorous vegetation whilst preserving the medicinal principles, M. Gallais dressed each of the plants with 100 grams of Peruvian guano. Being freely watered, the root then grew considerably and formed upon every side axillary buds, which produced in their turn leaves that were smaller than those which issued from the parent stem. Such buds, in developing, give rise in the prolonged stalk to changes which, upon section, become apparent as the marblings that are held as characteristics in commerce, and are the work of nature only. The plant was left during the second year, with only such attention as was necessary, to gather strength and to allow its cellular structure to become more compact by the concentration of its particular juices.
The collection was made at the end of the second year; in the case of the plant growing spontaneously, the Chinese are said not to make a collection until the end of the sixth year. The art of cultivating this plant for medicinal purposes, M. Gallais considers to lie not only in assisting the growth of the plant, but in favoring the development of the active principles, so that the plant may arrive in a couple of years at the age which, when growing wild, it attains in six. The known characters of French rhubarb he attributes to the collection having been made before the plants had arrived at maturity. As to reproduction, M. Gallais has obtained the best results with offshoots. At Ruffec the plant seeds with difficulty in the second year, and its, cultivation from seeds is not always successful, especially in rainy and cold seasons.
Every second year, in July or August, according to the season and the growth of the plant, the roots or prolonged stems were collected, and from these stalks a considerable number of offsets or buds were separated with a knife. The offshoots were then planted quincuncially in well-prepared soil, with a clear interval of a meter between each. As soon as the rainy and cold season set in these offsets commenced to develop, and continued during the autumn, forming rounded roots, which have supported the severest cold of the district, reaching 13° below zero.
Last year M. Gallais possessed eighteen plants, which, when pulled up, cleansed and dried, yielded 28 kilograms of product, described as being of good quality, and samples of which were exhibited to the Society. The gathering and drying, however, are looked upon by M. Gallais as more important operations than even the cultivation.
In the month of August the leaves of the plant become completely dry, and a period arrives when usually the soil surrounding the stem cracks and exposes the enormous roots. It is just at this time of apparent stagnation that M. Gallais pulls up the roots and "divides them most artistically into pieces to imitate those imported, whether from Tartary, Russia or Persia." These pieces are cleansed carefully and thrown at once into clean water that has been acidulated by some vinegar or a few drops of sulphuric acid, in order to prevent their becoming blackened or taking a bad color through exposure to the air. After a momentary immersion they are drained on hurdles and placed immediately in a stove at a temperature of 30°C. This operation has for its object to form a hard casing around the pieces, to compress the juice and to prevent mouldiness and consequent fermentation. After some days of continued drying, the pieces are strung upon cords so as to form large chaplets, and these are hung in a bake-house or kitchen chimney, or, when the quantity makes it worth while, in a stove. It is said that the Tartars attach small chaplets of rhubarb to the horns of their goats and sheep, and thus dry them by exposure to the sun's rays. M. Gallais thinks, however, that another account is more correct, which says that the rhubarb, cut into fragments and cleansed, is placed by the natives upon slowly heated stones, and carefully turned from time to time, being afterwards strung to complete the drying process. He is inclined to believe, however, that a quicker drying would be preferable, and proposes to place some of his next yield in an oven immediately after the removal of the bread.
Last year M. Gallais made the experiment of drying the root in the sun, but the result was not satisfactory. The thick pieces dried slowly and became completely decolorized, instead of retaining their dirty yellow tint, whilst the cellular tissue underwent a considerable alteration, due to a slight fermentation. M. Gallais considers that these alterations would be prevented by a rapid drying, and the juice being concentrated in the interior of the piece its aroma would be preserved, whilst the pieces would consequently acquire a commercial value in proportion to their thickness.
M. Gallais' operations have as yet been carried on upon a limited scale, but he makes an estimate in which he values the product at six francs per kilogram, from which it would appear that the cultivation could be carried on profitably.—Phar. Jour. and Trans., March 12.
The American Journal of Pharmacy, Vol. 53, 1881, was edited by John M. Maisch.