A rose is either a woody perennial flowering plant of the genus Rosa (/ˈroʊzə/),[4] in the family Rosaceae (/roʊˈzeɪsiːˌiː/),[4] or the flower it bears. There are over three hundred species and tens of thousands of cultivars.[5] The plants range in size and form, from trailing and erect shrubs to climbers up to 7 metres (23 ft) in height. Sharp prickles appear on the stems of many species.[6] Their flowers vary in size and shape and are usually large and showy, in colours ranging from white through pinks, reds, oranges and yellows.

Most species are native to Asia, with smaller numbers native to Europe, North America, and Northwest Africa.[6] Species, cultivars and hybrids are all widely grown for their beauty and often are fragrant. Different species hybridize easily, and this has been used in the development of the wide range of garden roses. Roses have acquired cultural significance in many societies.

EtymologyThe name rose comes from Latin rosa, which was perhaps borrowed from Oscan, from Greek ῥόδον rhódon (Aeolic βρόδον wródon), itself borrowed from Old Persian wrd- (wurdi), related to Avestan varəδa, Sogdian ward, Parthian wâr.[7][8]

BotanyThe leaves are borne alternately on the stem. In most species, they are 5 to 15 centimetres (2 to 6 in) long, pinnate, with (3–) 5–9 (−13) leaflets and basal stipules; the leaflets usually have a serrated margin, and often a few small prickles on the underside of the stem. Most roses are deciduous but a few (particularly from Southeast Asia) are evergreen or nearly so.

ThornsThe sharp growths along a rose stem, though commonly called thorns, are technically prickles, outgrowths of the epidermis (the outer layer of tissue of the stem), unlike true thorns, which are modified stems. Rose prickles are typically sickle-shaped hooks, which aid the rose in hanging onto other vegetation when growing over it.

Some species such as Rosa rugosa and R. pimpinellifolia have densely packed straight prickles, probably an adaptation to reduce browsing by animals, but also possibly an adaptation to trap wind-blown sand and so reduce erosion and protect their roots (both of these species grow naturally on coastal sand dunes). Despite the presence of prickles, roses are frequently browsed by deer. A few species of roses have only vestigial prickles that have no points.[citation needed]

Plant geneticist Zachary Lippman of Cold Spring Harbor Laboratory found that prickles are controlled by the LOG gene.[9][10] Blocking the LOG gene in roses reduced the thorns (large prickles) into tiny buds.