Notes from a plant nerd: Rhododendron, showman of the Southern Apps
Throughout Southern Appalachia, rhododendrons can be found growing and blooming. And what a show they put on. With flower colors running from white, to pink, to purple with large and small flowers, rhododendrons are among the most iconic flowers in all of Western North Carolina and can be found growing in most of the many and varied ecosystems in these mountains.
Rhododendrons are a woody shrub in the heath/heather family of plants, aka Ericaceae. Other plants that are in the heather family include sourwood trees (Oxydendron arboretum), blueberry and cranberry (Vaccinium sp.), pipsissewa (Chimaphala maculata), and even the odd and surprising ghost pipe (Monotropa uniflora). Plants in this family have a tendency towards thriving in acidic soil conditions, which is great since so many of the soils in these mountains fall on the acidic side due to the underlying geology. When it comes to growing a vegetable garden, acidic soils are not ideal and are often mitigated with limestone. There is no need to amend most soils around us here, if you are growing Rhododendrons or other Ericaceous plants, as they love growing in acidic soil.
Depending on where you look, and what authority you follow, there are anywhere from three to five species of rhodies, as they are affectionately called, that live in and around these southern mountains. I tend to follow the botanical work of Dr. Alan Weakley of the UNC Chapel Hill Herbarium when it comes to species accounts and botanical names. And, according to Weakley the five rhodies that live in WNC are the rosebay rhododendron (Rhododendron maximum) with light pink to whiteish flowers and large leaves; Catawba rhododendron (Rhododendron catawbiense) that mostly live at higher elevations and have purple flowers and large leaves; Carolina rhododendron (Rhododendron carolinianum) also found at high elevations and having smaller leaves and pink to whiteish flowers; piedmont rhododendron (Rhododendron minus) also with small leaves and pink to whiteish flowers but found growing at lower elevations, including outside of the mountains; and one of the newest to be classified and given a name, the rare Smoky Mountains rhododendron (Rhododendron smokianum) with deep purple flowers that can found only at the highest elevations of the Great Smoky Mountains National Park.
Rhododendrons have some mountain lore associated with them. During drought, or deep freezes in the winter, rhodies will curl their leaves inwards to create a microclimate as a form of protection. In drought, the inward curl helps to trap and funnel moisture while decreasing surface area exposed to the sun. In winter, at temperatures below the mid-twenties, the leaves are curled to hold heat and protect from freezing.
Mountain folk referred to rhododendrons as “laurels” and called mountain laurel (Kalmia latifolia) “ivy” so that place names around the mountains like Ivy Creek or the Big Ivy are referring to mountain laurel, while Laurel Knob, Laurel Valley and Laurel Creek are all referring to rhododendrons. Common names like ivy and laurel can be confusing, as many plants can share the same common name, or a plant can have many different common names.
To avoid confusion, plants also have scientific, or botanical, names that are written in a form of Latin that is called the binomial system of classification. There are rules to writing botanical names that include always capitalizing the genus name, and never capitalizing the specific epithet. These two names together are the species name. Also, botanical Latin should be written in italics, or underlined. You can see examples of this throughout this article. Other conventions you will find in botanical Latin is the use of “sp.” for “species” or “spp.” when referring to more than one type species.
Many people are intimidated by botanical Latin, not realizing how important and helpful it can be to learn these names for plants. In fact, as you can see from this article, you already know some botanical Latin. The genus of rhododendron is Rhododendron. Where things can be confusing, however, is when we learn that the plants we refer to as azaleas are also in the Rhododendron genus. We will learn more about azaleas in a future column.