Rose

Rose, common name for a family of flowering plants with many important fruit and ornamental species, and for its representative genus. Worldwide in distribution, the rose family contains about 107 genera and 3,100 species.

II ROSE FAMILY

Rose Varieties The more than 20,000 varieties of cultivated rose are carefully bred for qualities such as number and shape of petals. Pictured here are (top, left to right) Mrs. John Laing (perpetual, blooming in early summer and again in autumn), Just Joey (hybrid tea, with just a few large blossoms on each plant), Iceberg (floribunda, a cluster-flowered bush rose), Eglanteria (wild, with a thorny stem and a single layer of five petals in each flower); (bottom) Peace (hybrid tea), Old Blush China (China rose, blooming once a season), the Fairy (polyantha, a leafy shrub with clusters of dwarf blossoms), and Mme. George Staechelin (climbing, its many-blossomed arching vines trainable to trellises and fences).Dorling Kindersley About 70 genera of the rose family are cultivated for food, ornament, flowers, timber, or other uses. Although worldwide in distribution, the family is most abundant in north temperate regions and contains many of the most important fruit trees grown in temperate areas. These include apple, pear, peach, plum, cherry, apricot, almond, nectarine, loquat, and quince. The rambling, usually thorny blackberry, dewberry, and loganberry are members of a genus of the rose family that also includes the raspberry. The strawberry is also a member of the family. In addition, the family contains many important ornamentals: cinquefoil, hawthorn, spiraea, cotoneaster, firethorn, flowering cherry, flowering quince, and rowan.

III ROSE GENUS AND HYBRIDS

Roses of the rose genus are prickly shrubs, sometimes with scrambling or trailing stems. The leaves are pinnately compound with stipules (leaf-like appendages) fused to the base of the leaf-stalk. The flowers have five sepals and (in wild species) five petals, numerous stamens, and pistils. The flowers come in various colours, including shades of red, pink, yellow, and white. The fruit is the well-known hip, a swollen and thinly fleshed hypanthium (cup-shaped receptacle) enclosing the dry achenes.
The rose has been grown and appreciated for its fragrance and beauty since ancient times, and today is the most popular and widely cultivated garden flower in the world. Many species are important in perfumery, such as the damask rose, and others have applications in medicine. The genus contains some 100 species, most of them native to the North Temperate Zone. Some roses are cultivated in their natural form, but most of the more than 20,000 cultivars are the result of careful hybridization and selection from a few species. The cultivars are classed either as old roses—that is, plants that have essentially reached the end of their horticultural development, with no new varieties having been introduced in the past 60 years—or as contemporary roses—that is, plants that are currently being hybridized and selected for new forms. Several hundred new contemporary rose cultivars are introduced each year.
The classification of cultivated roses is complicated, because of the great numbers of cultivars involved and the amount of artificial hybridization that has taken place. Generally, the classes of old roses are based on selection from one or a few ancestral species or hybrids. Among the popular classes are the hybrid perpetuals, or remontant roses, which produce large, fragrant double flowers in early summer and fewer flowers in autumn. The class of polyantha roses includes many dwarf forms, with flowers produced in dense clusters. Tea roses and China roses are old-rose classes from which the contemporary hybrid tea roses have been derived through hybridization with hybrid perpetual roses. Hybrid tea roses are less hardy but more recurrent-blooming than the old hybrid perpetuals and have a much wider variety of colour and flower form. Many other contemporary-rose classes are based on the hybrid tea roses—for example, floribunda roses were derived from crosses between hybrid tea roses and hybrid polyantha roses, the latter in turn being based on crosses between the old polyantha roses and hybrid tea roses.