Learning the scientific names of plants is challenging for horticulturists at all levels. If you have been gardening or landscaping for a while, you have doubtless memorized the Latin genus and species names of many plants and can quickly find what you are looking for in a catalog or reference book. Knowing the accepted scientific names of plants is important for correct identification and clear communication with others. Despite being named in a dead language, the scientific monikers of plant species are not static. Many common landscape plant names have changed in recent years as scientists have learned more about species and their relationships to each other, leading some species to be reclassified and renamed. Before launching into the specifics, here is a quick primer on how plants are named.
The Basics of Plant Naming
In the mid-eighteenth century, a Swedish scientist named Carl Linnaeus developed a method for naming, ranking, and classifying plants that is still in use today (with many changes). Linnaeus gave all plant species a two-word “binomial” name consisting of the genus and species. It is still the basic structure of the modern naming system. Plants that are very similar and closely related are assigned to the same genus, and each is given a unique species name. For example, spotted geranium and bigroot geranium have the same genus (Geranium) but different species names (maculatum and macrorrhizum respectively). Why are plant names in Latin? In Linnaeus’ time in the eighteenth-century, Latin was the language of science, and the tradition has continued. Latinized descriptive phrases give clues about the plant’s qualities (i.e. “alba” means white and “rubra” red).
While scientific names may seem unnecessarily complicated when you first start learning them, they do serve an important purpose. Plants generally have a common name and a scientific name. Common names are often descriptive of the plant, such as red maple, bleeding heart, or paper birch. There are problems with using common names though. The same species of plant may have two or more common names, with names varying from region to region, and some very different plants may even have the same common name. For instance, “geranium” is the common name used to refer to two different groups of plants. There are the hardy geraniums in the genus Geranium, and tender greenhouse geraniums that belong to the genus Pelargonium. When discussing landscape plants, it can be helpful to describe the species you mean by its scientific name for the sake of clarity.
Changing Plant Names
Linnaeus used physical characteristics to group plants, a practice that continued until the late twentieth century when it became possible to study plant relationships through genetics. In some cases, genetic discoveries reinforced assumptions made through the examination of plant structures, but in others, DNA analysis showed that plants once thought to be related were quite different. This has led to plants being reclassified and therefore renamed. Names are changing at an accelerated pace, as genetic information allows for new understandings of plant relationships. In many cases, plants that were formerly grouped under a single species are reclassified into distinct species, or species previously classified in a particular genus are placed in other genera. For example, most of the species once classified in the genus Aster have now been placed in other genera, including Symphyotrichum, Doellingeria, Durybia, and Ionactis.
In a perfect world, there would be one true name for every plant, but scientists are constantly debating classifications. Many plants have more than one scientific name, but just one that is accepted as the most accurate. Current accepted names are what you will find in up-to-date botanical literature and serious garden writing. It usually takes years for the horticultural industry to adopt new plant names to avoid confusing clients. Eventually however, accepted names make their way into catalogues and horticulturists must make the mental shift. Do not be surprised if you start seeing the following landscape staples labelled by different names.
Symphyotrichum novae-angliae formerly Aster novae-angliae
New England Aster
Actaea racemosa formerly Cimicifuga racemosa
Black cohosh
Actea simplex formerly Cimicifuga simplex
Bugbane
Chamaepericlymenum canadense formerly Cornus canadensis
Bunchberry
Lamprocapnos spectabilis formerly Dicentra spectabilis
Bleeding heart
Eutrochium spp. formerly Eupatorium spp.
Joe Pye weed
Hylotelephium spectabile formerly Sedum spectabile
Sedum
Swida sericea formerly Cornus sericea
Red-osier dogwood
Swida amomum formerly Cornus amomum
Silky dogwood
Benthamidia florida formerly Cornus florida
Flowering dogwood
Benthamidia japonica formerly Cornus kousa
Kousa dogwood
— by Emma Erler, UNH Extension Field Specialist, emma.erler at unh.edu