Horticulturists, biologists, and many other professionals who may interact with colleagues who speak other languages or even slightly different regional dialects use Latin to identify, among other things, biological organisms. Latin names may be cumbersome to pronounce and daunting to spell, but are universal to those of us who use them. This is important because common names are so regionally variable.
For example, some of the European maples that we know as maples here are known as sycamores in England, but are known everywhere by their Latin name of Acer. Similarly, North American sycamores that are known as maples or plane trees in various regions are all likewise known everywhere by their Latin name of Platanus. The universality of Latin names therefore facilitates accurate identification.
Latin names are very helpful when researching plants. A tree known simply as a ‘cedar’ might be a calocedrus, arborvitae, juniper, cypress, chamaecyparis or a true cedar, just to name a few. Knowing that the particular tree is more specifically a ‘red cedar’ perhaps limits the possibilities to arborvitae or juniper. Identifying the tree specifically as a Juniperus virginiana will help us find the most accurate information about it, even though it is not really a cedar at all, but a juniper. Juniperus is the general ‘genus’ name of all junipers. Virginiana is the specific ‘species’ name of the particular juniper that is known locally as the Eastern red cedar. (‘Genera’ and ‘specie’ are plural for ‘genus’ and ‘species’.)
Latin names work like the names of cars. Buick, Chrysler and Mercury are all like genus names. Electra, Imperial and Grand Marquis are all like species names of particular Buicks, Chryslers and Mercurys. ‘Limited’, ‘Custom’ and ‘Brougham’ are like variety names, like ‘Variegata’, ‘Compacta’, and ‘Schwedleri’.
As universal as Latin names should be, a few sometimes get changed. This can be confusing, and causes some plants to become known more commonly by either their new or old name, as well as the other name as a ‘synonym’. For example, Dietes bicolor and Morea bicolor are the same plant; but not many know for certain which name is more correct. It is like when Datsun became Nissan, but was also known as Datsun for many years afterward.