This term is commonly misused in the horticultural trade, creating a lot of confusion. It is not being used often in accordance with international rules for naming plants. Lowest subdivision of a species ranking, used mainly to indicate a single trait that occasionally occurs in a population. Most taxonomists no longer use this rank, e.g., Cercis canadensis f. alba. A plant selected by humans for unique morphological or physiological traits and usually propagated asexually to maintain those traits, e.g., Ilex cornuta 'Dwarf Burford' Buxus microphylla var.
Name is set off in single quotes.
Azaleas - based artifically on breeding programs. Cabbages - based on similarities of morphological features. The hybrid is punctuated by placing the multiplication sign between the generic name and the epithet. Rank equivalent to species. Resultant rare cross of crossbreeding two species of different genera, e.g., x Cupressocyparis leylandii.