A rose is a perennial flower shrub or vine of the genus Rosa, within the family Rosaceae, that contains over 100 species and comes in a variety of colours. The species form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Most are native to Asia, with smaller numbers of species native to Europe, North America, and northwest Africa. Natives, cultivars and hybrids are all widely grown for their beauty and fragrance.
In horticulture roses are propagated by grafting or rooting cuttings. Cultivars are selected for their flowers, growth habit, cold and/or disease resistance, and many other factors. They may be grafted onto a rootstock that provides sturdiness, or (especially with Old Garden Roses) allowed to develop their own roots. Roses require 5 hours of direct sunlight a day during the growing season. Following blooming and exposure to frost roses enter a dormant stage in winter.
Many thousands of rose hybrids and cultivars have been bred and selected for garden use; most are double-flowered with many or all of the stamens having mutated into additional petals. In the early 19th century the Empress Josephine of France patronized the development of rose breeding at her gardens at Malmaison. As long ago as 1840 a collection numbering over one thousand different cultivars, varieties and species was possible when a rosarium was planted by Loddiges nursery for Abney Park Cemetery, an early Victorian garden cemetery and arboretum in England.
Twentieth-century rose breeders generally emphasized size and colour, producing large, attractive blooms with little or no scent. Many wild and "old-fashioned" roses, by contrast, have a strong sweet scent.
Description taken from Wikipedia: http://en.wikipedia.org/wiki/Rose