Learn botanical names; reduce surprises

There is a danger in using the common names of garden plants. Consider the case of a woman who wanted a native red maple (Acer rubrum) for her garden. She went to her favorite nursery in early spring, before leaves had unfurled, and asked whether they sold “red maples.” They did, and before the day was out she planted the naked tree in her garden.

A few weeks later the plant identified itself as a red-leafed cultivar of that invasive weed the Norway maple (Acer platanoides). This was quite a shock to someone who was endeavoring to create a native-plant landscape.

Buyers, beware! You cannot assume that the employees at the nursery know what you mean when you ask for a plant using its common name. A little knowledge of the scientific names of plants is a valuable tool, as necessary as the digging spade.

Let’s begin with the species name. Every plant has a unique binomial, or two-word name, such as Acer rubrum. Acer is the genus name, always capitalized; rubrum the specific epithet, never capitalized. The species name for red maple is Acer rubrum. While at least two maples share the common name of red maple, only one unique species has the scientific name of Acer rubrum.

Similar species are grouped in the same genus. For example, all maples are in the genus Acer. Gardeners owe this elegant invention of plant nomenclature to the Swedish botanist Carl Linnaeus, who in 1753 published “Species Plantarum.” (He made a similar contribution to animal nomenclature with the publication of “Systema Naturae” in 1758.) Before Linnaeus, botanical names were long, often beautiful descriptive phrases written in Latin. For example, the common briar rose was variously known as Rosa sylvestris inodora seu canina and as Rosa sylvestris alba cum rubore, folio glabro. Readers who took high school Latin can enjoy translating these names.

Gardeners also should understand the differences between varieties, cultivars and hybrids. A variety (or subspecies) is assigned to a group of naturally occurring individuals within a species that display a significant difference from the species. The differences are inheritable and reproduce true to type in succeeding generations. Varieties of woody plants often have a distinct geographic distribution. For example, the southern population of Acer rubrum is A. rubrum var. drummondii. Note that variety names are Latinized and come after the abbreviated designator “var.”

Horticulturally, the cultivar is the most important unit of classification. As the name implies, a cultivar is a group of cultivated plants, i.e. plants that do not occur in nature. A cultivar is distinguished from the species by any character, such as size, habit, leaf or flower color, cold tolerance, etc. The distinguishing characteristic(s) must be retained in future generations. While cultivars of woody plants are often propagated vegetatively from cuttings or by grafting, seed-grown varieties of vegetables and annual flowers that come true from seed also are considered cultivars.

There are at least 60 cultivars of Acer rubrum, including ‘October Glory,’ one of many selected for outstanding fall color. Note that cultivar names are always capitalized and enclosed in single quotation marks.

Many modern garden plants are hybrids, resulting from the chance or controlled crossing of two species (rarely plants from two genera). In areas where Acer rubrum and A. saccharinum (silver maple) grow together, a naturally occurring hybrid, A. x freemanii, occurs. The two species have crossed, resulting in a hybrid form with unique intermediate characteristics. Note that hybrids are written with a designator, the “x” before the hybrid-specific epithet.

You can find cultivars of hybrids. In fact, there are several cultivars selected from the Freeman hybrids. The gardener mentioned earlier could have asked for Acer rubrum x freemanii ‘Armstrong,’ a cultivar of red maple with a distinctly upright, narrow habit, and planted exactly what she wanted.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.