A cultivar is a cultivated variety of a plant species. Modern cultivars are often, but not necessarily, hybrids between species; they may equally well represent particularly desirable selections from populations of a single species. Cultivars generally are identified by uniquely distinguishing names, which may be registered and trademarked. Names of cultivars are registered with an International Cultivar Registration Authority and conform to the rules of the ISHS Commission Nomenclature and Cultivar Registration. There are authorities for different plant-groups.
Cultivars that are still being developed and not yet ready for release to seed companies often are coded with letters (signifying the university or other organization working on the variety) and numbers.
Some varieties are so well 'fixed' or established that they 'come true from seed,' meaning that the plants from a sowing will show very little variation. Such plants are better described by the more old-fashioned terms 'variety' 'selection' or 'strain,' and leaving the term 'cultivar' to plants that are vegetatively propagated, such as roses, Hemerocallis or iris.