Rosa(redirected from Rosas)
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(rose), a genus of plants of the family Rosaceae. There are approximately 400 wild species, distributed in the northern hemisphere. More than 200 species are found in the USSR. The plants are shrubs ranging in height from 15 cm to 2 cm. Some species form vine-like branches reaching 10 to 12 m in length. The shoots are usually covered with prickles. The leaves are alternate, oddly pinnate, naked or downy, and stipulate. The stipules are adnate to the petiole. The simple or double flowers measure 2 to 15 cm across and most often are fragrant. They are red, pink, white, yellow, orange, or lilac. The flowers are solitary or in umbellate-panicled inflorescences. The torus is urn-shaped. Achenes are usually enclosed in a fleshy false fruit.
Roses are distinguished by great variability; they readily form natural hybrids. Hybridization and selection have yielded numerous garden forms. Many wild species have been cultivated, including species native to China (China rose, R. chinensis; tea rose, R. odorata), Asia Minor (French rose, R. gallica; dam-ask rose, R. damascena), Afghanistan, Iran, Armenia (R. luted), the Far East, and southern Japan (rugosa rose, R. rugosa; R. multiflora).
Approximately 25,000 rose varieties and forms are used in ornamental horticulture. They are divided into three groups: deciduous shrubs, evergreen shrubs, and lianas. Deciduous rose shrubs form numerous root shoots. The flower-bearing shoots develop on shoots from the previous year. Flowering, occurring once a year in the spring, lasts 20 to 40 days. Roses in this group include Lambertian roses, Wichuraiana hybrids, a rugosa hybrid, Kordesii hybrids, Pimpinellifolia hybrids, Gallica hybrids, Centifolias hybrids, and Muscosa hybrids.
Evergreen rose shrubs are distinguished by intensive growth and prolonged flowering. The flower-bearing shoots appear on shoots from the previous year and on new shoots. To this group of roses belong noisettes, miniature China roses (R. indica var. vulgaris), Bourbons, tea roses, perpetual tea roses, hybrid teas, polyanthas, hybrid polyanthas, and hybrid-polyantha floribundas.
Roses belonging to the liana group are called climbing roses. The shoots reach a length of 10 to 12 m. Flowering occurs once a year in the summer. Climbing roses include R. multiflora and the memorial rose (R. wichuraiana).
Owing to their varietal diversity, abundant and prolonged flowering, and richness of color, hybrid teas and floribundas are the roses most widely cultivated as ornamentals. Hybrid teas are raised for cut flowers in the open ground and, especially, in greenhouses. They are the principal type of rose raised in sheltered ground for commercial purposes. Hybrid teas flower from March to November. The flowers, which are borne by long shoots, are solitary, large, double, and fragrant. Hybrid-polyantha floribundas are raised primarily for their beautiful flowers. Flowering is abundant and continuous.
Deciduous rose shrubs are planted in parks and gardens. They are winter-hardy, and they flower abundantly in the first half of the summer. Lambertian and Kordesii roses, which flower abundantly and continuously, reach a height of 2 m. The flowers, which are large and double, are pink, white, or red. They have a strong fragrance.
Evergreen rose shrubs and almost all deciduous rose shrubs are propagated vegetatively by budding or by cuttings. The dog rose (R. canina) is used as a stock. Budding stocks are set out in the spring in northern regions and in the autumn in southern regions. They grow well on sandy-loam, sandy, and clayey soils that have been fed organic and inorganic fertilizers. The plants cannot grow in poorly drained soil. After planting, the shrubs are pruned, leaving one to three shoots. Care includes fertilization (three to five times per summer), watering, tillage, winter mulching (with tree leaves, branches of coniferous trees, board frames), and pruning. Throughout the summer dead and weak branches and shoots are removed, as are shoots growing inside the shrub.
The petals of some species of rose, including the French rose, cabbage rose (R. centifolias), and damask rose, yield rose oil—a valuable aromatic essential oil. Species yielding rose oil are raised commercially in Bulgaria, the USSR, France, Turkey, Italy, and a number of other countries. In the 19th century the damask rose was imported into Russia from Bulgaria for the commercial production of rose oil. The following essential-oil rose varieties have been developed in the USSR: Red Crimea, Festival, Michurinka, Pionerka, and Tavrida. They are cultivated in Moldavia, the southern Ukraine, Krasnodar Krai, and the Caucasus. In 1933, 218 hectares (ha) were planted with oil-yielding roses; in 1973, more than 4,500 ha. The average petal yield is about 18 quintals per ha (on some farms, up to 30 quintals per ha).
The petals of some rose species are used to produce jam. The pulp of the fruits of many roses is used in vitamin manufacture, since it is rich in ascorbic acid (15–18 percent of the dry matter) and, to a lesser extent, vitamin P (Dahurian rose, R. beggeriana, cinnamon rose). The fruits and roots of some species are used in the preparation of tanning agents and dyes.
Rose insects include the rose scale, rose leaf roller, Ardis brunniventris, and Epitetranychus. Diseases include powdery mildew, rose rust, black spot, gray mold, and bacterial canker.
REFERENCESIzhevskii, S. A. Rozy, 2nd ed. Moscow, 1958.
Kiselev, G. E. Tsvetovodstvo, 3rd ed. Moscow, 1964.
Saakov, S. G., and D. A. Rieksta. Rozy. Riga, 1973.
Klimenko, V. N., and Z. I. Klimenko. Rozy, 3rd ed. Simferopol’, 1974.
S. G. SAAKOV