Names help us identify something, to see it as different from something else. Scientists have developed a system for naming organisms that reflects their relationship with one another as well as separating them. Common names such as "cedar" may be applied to trees that are not even remotely related, or a single plant may have 10 or more common names. To know exactly which plant is being referred to, it is necessary to use scientific names.
Swedish physician and naturalist Carl Linnaeus developed the formal system of naming a plant by genus and species called binomial nomenclature. Each name is either in Latin or is a Latinized word. It has been adopted all over the world as a standard for naming both plants and animals and expanded to include both larger, more general categories and smaller groups within a species.
The main benefit of this system is clarity. Everyone knows which plant the name applies to. It is also reasonably stable, with only occasional changes.
Plants in a single species, or even a single community, may be quite variable, so Rosa rugosa may apply to individuals with different shades of pink in the flowers. Each individual has a particular genotype, the genetic blueprint that produces that plant. There are standards for naming communities, plants propagated from a single individual and hybrids between species.
If a group of plants share characteristics that can be passed on through natural reproduction, seeds and spores, that is known as a variety. These breed true unless an individual from another population is introduced. Annuals may be selected for a certain shade of color and, after a number of generations, will breed true since the genes for other shades are now missing.
The standard way of writing the name of a variety is the genus, species and then the word "variety" abbreviated as "var." plus the name. For instance, a white rugosa rose may be Rosa rugosa var. alba.
Propagating one plant asexually gives a cultivar, the abbreviation for "cultivated variety." This may be a naturally occurring wild seedling or a selection from seedlings raised and selected for certain attributes such as flower color.
Cultivars are written within single quotation marks after the genus and species, and the name is capitalized. For instance, one of the cultivars of the Rugosa rose is Rosa rugosa 'Blanc Double de Coubert.'
When a plant from one species is crossed with one of another species, the result is said to be a hybrid. This is indicated in the name by an "x" before the second name.
If a plant comes from one of the rare crosses between plants of different genera, the "x" is placed before the new genus. For instance, hybrids between limes and kumquats are called limquats, x Citrofortunella.