5 Conventions for Binomial Nomenclature

Botanical nomenclature is the scientific system of naming plants. The naming of plants is governed by two sets of published rules: The International Code of Nomenclature for algae, fungi, and plants and the International Code of Nomenclature for Cultivated Plants. These rules establish a worldwide standard of reference for naming plants. By convention, when written in text a botanical name is always italicized or underlined, and the first letter of the genus name is always capitalized.

The following summarizes the basic rules regarding the writing of botanical names for plants:

• The generic epithet of a botanical name is always capitalized (e.g., Salvia, Impatiens), and is underlined or italicized except where it is also used as a common name, as in salvia or impatiens. Within text or in a list – but only where unambiguous – the genus name is often abbreviated to the first letter, for example, Rosa rugosa, R. moyesii, R. acicularis.
• The specific epithet of a botanical name is always lower case, and is underlined or italicized in text, as Gaultheria shallon or Gaultheria shallon. If only the genus of a plant is known, the specific epithet is abbreviated as sp. (designating a single species) or spp. (more than one species).
• Hybrids, produced from breeding 2 or more different species (interspecific), are noted by a multiplication sign between the genus and specific epithet, for example, Forsythia × intermedia.
• Hybrids produced from crosses between genera (intergeneric), are noted by a multiplication sign before the genus, for example, ×Solidaster luteus which has the following parentage, (Solidago canadensis × Aster ptarmicoides).
• Subspecies are abbreviated ssp. or subsp. The subspecies epithet is not capitalized but is underlined or italicized, for example Acer glabrum ssp. douglasii
• Variety or more officially, varietas, is abbreviated var. The variety epithet is not capitalized but is underlined or italicized, as in this example, Clematis montana var. rubens
• Form or more officially, forma, is abbreviated f. (or sometimes fa.). For example, Cornus florida f. rubra.
• Cultivars usually have vernacular names, are not italicized or underlined, and all words are capitalized and usually in single quotes. For example, Astilbe chinensis ‘Pumila’ or Ilex aquifolium ‘Ferox Argentea’.
• Group: This describes a group of unnamed tree seedlings, for example Picea pungens Glauca Group describes all the un-named seedlings with blue foliage that are available in the nursery trade.  Groups names are not italicized or underlined, and all words are capitalized but are not in single quotes.
• The ™ designation indicates that the originator of the new plant, for example, Pyrus calleryana Aristocrat™, has applied for a trademarked name. The ® indicates that the plant name is a registered trademark, such as in Pyrus calleryana Chanticleer®. The trademark name is often the “selling name” of the plant, which may differ from the cultivar name. eg. Weigela florida ‘Alexandra’ is sold under the moniker Wine & Roses® weigela.