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(stork’s-bill), a genus of plants of the family Geraniaceae. The plants are herbs or subshrubs whose stem is sometimes thickened and succulent at the base. The leaves are mostly opposite, stipulate, and lobed or pinnatisect; frequently they have glandular pubescence. The irregular flowers are in axillary umbel-like inflorescences.
There are approximately 250 species of stork’s-bill, distributed primarily in southern Africa. One species, P. endlicherianum, is found in Asia Minor and Transcaucasia, and four species are encountered in Australia. Many species, known as geraniums, were introduced into cultivation in the early 18th century for essential oil and as ornamentals.
In the Mediterranean countries and the USSR (the Crimea, the Caucasus, Middle Asia), the rose geranium (P. roseum), a complex hybrid of many species (P. radula, P. capitatum), is cultivated for essential oil. A densely branched subshrub, the rose geranium has long-petioled leaves, which are alternate, cordate, and divided into five to seven lobes. The flowers are in dense umbel-like inflorescences and the corolla is pink. Fruits form very rarely.
The rose geranium requires warmth, light, and moisture; at a temperature of 3° -5°C, the plant dies. In the USSR it is cultivated as an annual plant. The plant is also grown in France, Algeria, Spain, and Italy. Plantings in the USSR in 1973 occupied 1,200 hectares (ha) in the Georgian SSR, 1,600 ha in the Armenian SSR, and 960 ha in the Tadzhik SSR. The essential oil is obtained from the fresh leaves and stems and contains 65 to 70 percent citronellol. Oil content is from 0.09 to 0.16 percent of the weight of the raw mass. In the USSR, hybrid varieties containing up to 0.5 percent essential oil have been produced. The oil is used by the perfume, soap, and food industries.
The rose geranium is propagated by cuttings taken from shoot tips. The nurselings are raised in greenhouses. The cuttings are prepared in the fall; a cutting of 10–12 cm in length is considered standard. Up to 400 to 500 cuttings are planted per 1 sq m of protected soil. The rooted cuttings are kept until spring at a temperature of 4°–5°C. Standard nurselings have a stem no less than 15 cm in height. The soil in which the rose geraniums are planted is plowed in the fall to a depth of 25 to 30 cm. Manure and inorganic fertilizers significantly increase the crop harvest and the yield of essential oil. The nurselings are planted in April and are harvested once or twice during dry weather. The foliage is delivered immediately to a plant for processing, since it quickly loses its essential oil. Hybrids of P. graveolens and zonal geraniums—hybrid varieties produced by crossing P. inquinans and P. zonale—are popular as houseplants and greenhouse plants. The trailing varieties of Pelargonium, which have originated primarily from P. peltatum, are planted in gardens and parks.
REFERENCEEfiromaslichnye kul’tury. Edited by A. A. Khotin and G. T. Shul’gin. Moscow, 1963.
K. D. ZALOZNYI and S. S. MORSHCHIKHINA