Rose in the context of Desert rose (crystal)

A cultivar is a kind of cultivated plant that people have selected for desired traits and which retains those traits when propagated. Methods used to propagate cultivars include division, root and stem cuttings, offsets, grafting, tissue culture, or carefully controlled seed production. Most cultivars arise from deliberate human manipulation, but some originate from wild plants that have distinctive characteristics. Cultivar names are chosen according to rules of the International Code of Nomenclature for Cultivated Plants (ICNCP), and not all cultivated plants qualify as cultivars. Horticulturists generally believe the word cultivar was coined as a term meaning "cultivated variety".

Popular ornamental plants like roses, camellias, daffodils, rhododendrons, and azaleas are commonly cultivars produced by breeding and selection or as sports, for floral colour or size, plant form, or other desirable characteristics. Similarly, the world's agricultural food crops are almost exclusively cultivars that have been selected for characters such as improved yield, flavour, and resistance to disease. Since the advent of genetic engineering in the 1970s and the rise of its application in crop breeding in the 1980s, very few wild plants are used as commercial food sources. Trees used in forestry are also special selections grown for their enhanced quality and yield of timber, for example American timber company Weyerhaeuser is the leading grower of genetically modified Douglas-fir trees, one of the most commonly harvested trees.

Rosaceae (/roʊˈzeɪsiː.iː, -si.aɪ, -si.eɪ/), the rose family, is a family of flowering plants that includes 4,828 known species in 91 genera.

The name is derived from the type genus Rosa. The family includes herbs, shrubs, and trees. Most species are deciduous, but some are evergreen. They have a worldwide range but are most diverse in the Northern Hemisphere.

Rose window is often used as a generic term applied to a circular window, but is especially used for those found in Gothic cathedrals and churches. The windows are divided into segments by stone mullions and tracery. The term rose window was not used before the 17th century and comes from the English flower name rose.

The name "wheel window" is often applied to a window divided by simple spokes radiating from a central boss or opening, while the term "rose window" is reserved for those windows, sometimes of a highly complex design, which can be seen to bear similarity to a multi-petalled rose. Rose windows are also called "Catherine windows" after Saint Catherine of Alexandria, who was sentenced to be executed on a spiked breaking wheel. A circular window without tracery such as are found in many Italian churches, is referred to as an ocular window or oculus.

Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the corolla. Petals are usually surrounded by an outer whorl of modified leaves called sepals, that collectively form the calyx and lie just beneath the corolla. The calyx and the corolla together make up the perianth, the non-reproductive portion of a flower. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished sepals and petals. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots.

Although petals are usually the most conspicuous parts of animal-pollinated flowers, wind-pollinated species, such as the grasses, either have very small petals or lack them entirely (apetalous).

Cut flowers are flowers and flower buds (often with some stem and leaf) that have been cut from the plant bearing it. It is removed from the plant for decorative use. Cut greens are leaves with or without stems added to the cut flowers for contrast and design purposes.

Floral design professionals work at florist shops (floristry) and use their design skills and experience with many types of flowers and greens to create works of art with flowers.

There is significant disagreement over the number of true rose species. Some species are so similar that they could easily be considered varieties or even forms of a single species. Lists of rose species usually show more than 320. The range of 320 to 350 is accepted by most botanists, but as Liberty H. Bailey has pointed out, the extreme lumpers Bentham and Hooker only allowed for 30 species, while the extreme splitter Michel Gandoger allowed 4,266 species just in Europe and West Asia.

Garden roses are predominantly hybrid roses that are grown as ornamental plants in private or public gardens. They are one of the most popular and widely cultivated groups of flowering plants, especially in temperate climates. An enormous number of garden cultivars has been produced, especially over the last two centuries, though roses have been known in the garden for millennia beforehand. While most garden roses are grown for their flowers, often in dedicated rose gardens, some are also valued for other reasons, such as having ornamental fruit, providing ground cover, or for hedging.

The cultivars are classified in a number of different and overlapping ways, generally without much reference to strict botanical principles. Taking overall size and shape, the most common type is the bush rose, a rounded plant from 2 foot up to about 7 foot tall, above which height roses generally fall into the "'climbing and rambling'" class, the latter spreading wider; support is needed for these. There are also miniature roses, generally small bushes, and low sprawling ground cover roses, both up to about 15 inches tall. Most modern roses are propagated by budding onto rootstocks much closer to wild species; in "standard" shapes there is a single bare stem, with the graft at the top of that. Shrub roses are a rather loose category that include some of the original species and cultivars closely related to them, plus cultivars that grow rather larger than most bush roses. Technically all roses are shrubs. In terms of ancestry, roses are often divided into three main groups: Wild, Old Garden, and Modern Garden roses, with many subdivisions of these.