In naming cultivated plants, a Group (formerly cultivar group) is a formal classification category, under the International Code of Nomenclature for Cultivated Plants (ICNCP):
- ICNCP Art. 3.1: "a formal category for assembling cultivars, individual plants or assemblages of plants on the basis of defined similarity."
The term "Group" (with a capital G) was introduced in the 2004 ICNCP, replacing the "Cultivar-group" of the 1995 ICNCP.
A Group is united by some common trait; for example there may be a Group of yellow-flowering cultivars, a Group of cultivars with variegated leaves, a Group of cultivars resistant to a particular disease, etc. A cultivar may belong to more than one Group (for example, it may be yellow-flowering, with variegated leaves and resistant to the disease at one and the same time, or another time).
- ICNCP Art 9, Ex 10: "Solanum tuberosum 'Desiree' may be designated part of a Maincrop Group and a Redskin Group since both such designations may be practical to buyers of potatoes ..." [capitalization in original, as required by the ICNCP]
Another reason for designating a Group is when a well-known plant loses its taxonomic status (e.g. it ceases to be a "good" species or subspecies and becomes a synonym). Its botanical epithet may be retained in a "Group epithet". For example, Tetradium hupehense is sometimes regarded as being part of Tetradium daniellii, and the plants in question may then be referred to as Tetradium daniellii Hupehense Group.
Every word in a Group epithet (name) is capitalised, except where not permitted by English-language custom, e.g. conjunctions, prepositions (that do not begin the epithet), and words following a hyphen (that are not proper names). (Art. 21.3)
- Brickell, C.D. et al. (eds) (2009). "International Code of Nomenclature for Cultivated Plants". Scripta Horticulturae (8th ed.) (International Society of Horticultural Science) 10: 1–184. ISBN 978-0-643-09440-6.