A Group (previously cultivar-group) is a formal category for cultivated plants that share a defined characteristic according to the Cultivated Plant Code. In 2004, the Code started using the term "Group" (always written with a capital "G") in place of "cultivar-group", which had previously been the category's name since 1995.
A Group is usually united by a distinct common trait, and often includes members of more than one species within a genus. For example, early flowering cultivars in the genus Iris form "Iris Dutch Group". A plant species that loses its taxonomic status in botany, but still has agricultural or horticultural value, meets the criteria for a Group and its former botanical name can be used as its Group name; for example, Hosta fortunei is usually no longer recognized as a species, and the Code states that the epithet 'fortunei' can be used to form Hosta Fortunei Group.
Every word in a Group name is capitalized unless that conflicts with linguistic custom; for example, lowercase is used for conjunctions and prepositions except in the first word of the Group name and ending with "Group"; for example, Lilium Darkest Red Group, Neofinetia falcata Hariba Group.
- Grex (horticulture), a taxonomic category for hybrid orchids, defined by parentage rather than by characteristics
- Polyploid, having extra sets of chromosomes. Polyploidy is a characteristic sometimes used to define a Group.
- Brickell, C.D. et al. (eds) (2009). "International Code of Nomenclature for Cultivated Plants" (PDF). Scripta Horticulturae (8th ed.). International Society of Horticultural Science. 10: 1–184. ISBN 978-0-643-09440-6.
Art. 3.1: "a formal category for assembling cultivars, individual plants or assemblages of plants on the basis of defined similarity."
- "Groups", HORTAX: Cultivated Plant Taxonomy Group, retrieved 19 July 2016