Browsing through plant encyclopedias and garden catalogs or visiting botanical gardens and nurseries, one can see many varieties of offerings, each carrying a binomial, or two-name, Latin label comprising a particular plant’s genus, which is capitalized, and following it in lower-case, an epithet, or characterizing secondary name denoting its species. This epithet may refer to the plant’s original habitat: for instance, Pinus virginiana for the pitch pine native to eastern North America; to the plant collector who discovered it in the wild, perhaps fortunei if, as in the case of the rhododendron, it was first brought into cultivation by Robert Fortune (1812–1880); or to some other distinguishing characteristic such as white-flowered, in which case it might be called albiflorens.

At the moment I am looking at The Random House Book of Perennials, which both describes and illustrates with color photographs 1,250 plants. If I want to plant the lovely bell-shaped campanula, I can choose and probably buy one or more of several members of the family Campanulaceae. If I have a rock garden, I may want Campanula carpatica, which, as its name suggests, was discovered in the Carpathian mountains of Poland, Czechoslovakia, Romania, and western Russia. Or, I might want instead Campanula persicifolia, so named because its leaves resemble those of a peach tree. Its natural habitat, unlike that of the alpine Campanula carpatica, consists of meadows, open woods, and forest edges across most