A rose is a perennial plant of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in a number of colours from white through yellows and reds. Most species are native to Asia, with smaller numbers native to Europe, North America, and northwest Africa. Species, cultivars and hybrids are all widely grown for their beauty and fragrance. Rose plants range in size from compact, miniature roses, to climbers that can reach 7 meters in height. Species from different parts of the world easily hybridize, which has given rise to the many types of garden roses.
The leaves are borne alternately on the stem. In most species they are Template:Convert 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 South east Asia) are evergreen or nearly so.
The flowers of most species have five petals, with the exception of Rosa sericea, which usually has only four. Each petal is divided into two distinct lobes and is usually white or pink, though in a few species yellow or red. Beneath the petals are five sepals (or in the case of some Rosa sericea, four). These may be long enough to be visible when viewed from above and appear as green points alternating with the rounded petals. The ovary is inferior, developing below the petals and sepals. Roses are insect-pollinated in nature.
The aggregate fruit of the rose is a berry-like structure called a rose hip. Many of the domestic cultivars do not produce hips, as the flowers are so tightly petalled that they do not provide access for pollination. The hips of most species are red, but a few (e.g. Rosa pimpinellifolia) have dark purple to black hips. Each hip comprises an outer fleshy layer, the hypanthium, which contains 5–160 "seeds" (technically dry single-seeded fruits called achenes) embedded in a matrix of fine, but stiff, hairs. Rose hips of some species, especially the Dog Rose (Rosa canina) and Rugosa Rose (Rosa rugosa), are very rich in vitamin C, among the richest sources of any plant. The hips are eaten by fruit-eating birds such as thrushes and waxwings, which then disperse the seeds in their droppings. Some birds, particularly finches, also eat the seeds.
While the sharp objects along a rose stem are commonly called "thorns", they are technically prickles — outgrowths of the epidermis (the outer layer of tissue of the stem). (True thorns, as produced by e.g. Citrus or Pyracantha, are modified stems, which always originate at a node and which have nodes and internodes along the length of the thorn itself.) 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 Rosa pimpinellifolia have densely packed straight spines, 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.
Template:Further The genus Rosa is subdivided into four subgenera:
- Hulthemia (formerly Simplicifoliae, meaning "with single leaves") containing one or two species from southwest Asia, R. persica and Rosa berberifolia which are the only roses without compound leaves or stipules.
- Hesperrhodos (from the Greek for "western rose") contains Rosa minutifolia and Rosa stellata, from North America.
- Platyrhodon (from the Greek for "flaky rose", referring to flaky bark) with one species from east Asia, Rosa roxburghii.
- Rosa (the type subgenus) containing all the other roses. This subgenus is subdivided into 11 sections.
- Banksianae - white and yellow flowered roses from China.
- Bracteatae - three species, two from China and one from India.
- Caninae - pink and white flowered species from Asia, Europe and North Africa.
- Carolinae - white, pink, and bright pink flowered species all from North America.
- Chinensis - white, pink, yellow, red and mixed-color roses from China and Burma.
- Gallicanae - pink to crimson and striped flowered roses from western Asia and Europe.
- Gymnocarpae - one species in western North America (Rosa gymnocarpa), others in east Asia.
- Laevigatae - a single white flowered species from China
- Pimpinellifoliae - white, pink, bright yellow, mauve and striped roses from Asia and Europe.
- Rosa (syn. sect. Cinnamomeae) - white, pink, lilac, mulberry and red roses from everywhere but North Africa.
- Synstylae - white, pink, and crimson flowered roses from all areas.
Roses are best known as ornamental plants grown for their flowers in the garden and sometimes indoors. They have been also used for commercial perfumery and commercial cut flower crops. Some are used as landscape plants, for hedging and for other utilitarian purposes such as game cover. They also have minor medicinal uses.
The majority of ornamental roses are hybrids that were bred for their flowers. A few, mostly species roses are grown for attractive or scented foliage (such as Rosa glauca and Rosa rubiginosa), ornamental thorns (such as Rosa sericea) or for their showy fruit (such as Rosa moyesii).
Ornamental roses have been cultivated for millennia, with the earliest known cultivation known to date from at least 500 BC in Mediterranean countries, Persia, and China. Many thousands of rose hybrids and cultivars have been bred and selected for garden use as flowering plants. 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.
A few species and hybrids are grown for non-floral ornamental use. Among these are those grown for prominent hips, such as the flagon shaped hips of Rosa moyesii. Sometimes even the thorns can be treated as an attraction or curiosity, such as with Rosa sericea.
Roses are a popular crop for both domestic and commercial cut flowers. Generally they are harvested and cut when in bud, and held in refrigerated conditions until ready for display at their point of sale.
In temperate climates, cut roses are often grown in glasshouses, and in warmer countries they may also be grown under cover in order to ensure that the flowers are not damaged by weather and that pests and disease control can be carried out effectively. Significant quantities are grown in some tropical countries, and these are shipped by air to markets across the world.
Rose perfumes are made from attar of roses or rose oil, which is a mixture of volatile essential oils obtained by steam distilling the crushed petals of roses. An associated product is rose water which is used for cooking, cosmetics, medicine and in religious practices. The production technique originated in Persia then spread through Arabia and India, but nowadays about 70% to 80% of production is in the Rose Valley near Kazanluk in Bulgaria, with some production in Qamsar in Iran and Germany.Template:Citation needed The Kaaba in Mecca is annually washed by the Iranian rose water from Qamsar Template:Citation needed. In Bulgaria, Iran and Germany, damask roses (Rosa damascena 'Trigintipetala') are used. In the French rose oil industry Rosa centifolia is used. The oil is transparent pale yellow or yellow-grey in colour. 'Rose Absolute' is solvent-extracted with hexane and produces a darker oil, dark yellow to orange in colour. The weight of oil extracted is about one three-thousandth to one six-thousandth of the weight of the flowers; for example, about two thousand flowers are required to produce one gram of oil.
The main constituents of attar of roses are the fragrant alcohols geraniol and l-citronellol; and rose camphor, an odourless paraffin. β-Damascenone is also a significant contributor to the scent.
Rose water, made as a byproduct of rose oil production, is widely used in Asian and Middle Eastern cuisine. The French are known for their rose syrup, most commonly made from an extract of rose petals. In the United States, this French rose syrup is used to make rose scones and marshmallows.
The rose hip, the fruit of some species, is used as a minor source of Vitamin C.
Rose hips are occasionally made into jam, jelly, and marmalade, or are brewed for tea, primarily for their high vitamin C content. They are also pressed and filtered to make rose hip syrup. Rose hips are also used to produce Rose hip seed oil, which is used in skin products and some makeup products.
The fruits of many species have significant levels of vitamins and have been used as a food supplement (see previous section). Many roses have been used in herbal and folk medicines. Rosa chinensis has long been used in Chinese traditional medicine. This and other species have been used for stomach problems, and are being investigated for controlling cancer growth.
Roses are a favored subject in art and therefore used in various artistic disciplines. They appear in portraits, illustrations, on stamps, as ornaments or as architectural elements. The Luxembourg born Belgian artist and botanist Pierre-Joseph Redouté is known for his detailed watercolours of flowers, particularly roses.
Henri Fantin-Latour was also a prolific painter of still life, particularly flowers including roses. The Rose 'Fantin-Latour' was named after the artist.
Other impressionists including Claude Monet, Paul Cézanne and Pierre-Auguste Renoir have paintings of roses among their works.
The long cultural history of the rose has led to it being used often as a symbol.
Pests and diseases
Roses are subject to several diseases. The main fungal diseases affecting the leaves are rose black spot (Diplocarpon rosae), rose rust (Phragmidium mucronatum), rose powdery mildew (Sphaerotheca pannosa) and rose downy mildew (Peronospora sparsa). Stems can be affected by several canker diseases, the most commonly seen of which is stem canker (Leptosphaeria coniothyrium). Diseases of the root zone include honey fungus (Armillaria spp.), verticillium wilt, and various species of phytophthora.
Fungal leaf diseases affecting roses are best prevented by choosing to grow cultivars and species known to be less susceptible to attack, and by using a preventative fungicidal spray program (rather than by trying to cure an infection after it emerges on the plant). After disease is visible, spread can be minimized through pruning and the use of fungicides, although the actual infection cannot be reversed. Stem cankers are best treated by pruning out infection as soon as it is noticed. Root diseases are not usually possible to treat, once infection has occurred; the most practical line of defence is to ensure that growing conditions maximise plant health and thereby prevent infection. Phytophthora species are waterborne and therefore improving drainage and reducing waterlogging can help reduce infection.
The main pest affecting roses is the aphid (greenfly), which sucks the sap and weakens the plant. (Ladybugs are a predator of aphids and should be encouraged in the rose garden.) In areas where they are endemic Japanese beetles (Popillia japonica) take a heavy toll on rose flowers and foliage; rose blooms can also be destroyed by infestations of thrips (Thysanoptera spp). Roses are also used as food plants by the larvae of some Lepidoptera (butterfly and moth) species; see list of Lepidoptera that feed on roses. The spraying with insecticide of roses is often recommended but should be done with care to minimize the loss of beneficial insects.
- Template:Cite web
- Jack Goody. The culture of flowers. Cambridge University Press, 1993
- [www.foodnet.cgiar.org/market/Uganda/reports/Roses.PDF FOODNET Uganda 2009. Commercialisation bulletin: Fresh cut roses]