A walk along the lower trail bordering Cabin John Creek requires a bit of boulder hopping. A relatively flat path gives way in a certain section to a world of jutting rocks, exposed roots, and low-growing trees—the most enchanted part of our local forest. The boulders are often topped by Polypody ferns, also known as rock cap ferns for their penchant to grow in depressions on rocks. If you stumble on a root and reach for a nearby shrub to keep your balance, more likely than not, you would be grasping the leathery evergreen leaves of the mountain laurel or a broom- like branch of witch hazel. And if you did fall, you might find yourself lying prone next to mapleleaf viburnum. These three shrubs—mountain laurel, witch hazel, and mapleleaf viburnum—are among the most common in the wildest reach by the creek, but only where the geology underlying the path beneath your feet is different from the rest of the trail.
An expert on the flora of the Great Smoky Mountains, the botanist Dan Pittillo, once shared this insight with me while on a nature hike: “If you want to be a botanist, become a geologist.” It turns out that this puzzling piece of advice makes more sense the longer you spend in nature looking at plants. If you know the underlying geology and soils of an area, you can often predict the plants and plant communities to be found there. A lot of plants, especially the more rare ones, prefer, or are limited to, a distinct substrate where they compete best for resources. And where the boulders composed of schist and gneiss— two common coarse-grained metamorphic rocks—create an obstacle course along the creek, the rarest plants along the Potomac grow: crane fly orchid, Adam-and-Eve orchid, rattlesnake plantain orchid, hepatica, and spotted wintergreen. And shading them from above is that trio of shrubs worthy of our attention as ecologists and a place in our gardens as restorationists. Fortunately for us, while all three of these plants are most common in the rocky stretches, they are easy to grow in the flat smooth soils of backyard Cabin John.
Mountain laurel is typically a plant of the mountains and the state flower of Connecticut and Pennsylvania. For anyone who has hiked or driven along the slopes of Sugarloaf Mountain near Comus, Maryland in early May, the magnificent white or pink blossoms of mountain laurel greet you. So to see so much mountain laurel in the lowland forests around us is a botanical treat. It is likely the distinct geologic conditions of those schist and gneiss outcrops that allow the shrub to grow at this lower elevation. The abundant flowers attract the interest of native bumblebees and the fragrance of the blossoms has been compared to that of grape bubble gum (that was meant as a compliment by a gum chewing botanist). The mountain laurel is in the same family as Rhododendron (in Latin, the rose trees). If you’re thinking of planting in your flower bed some rose bushes this year, please reconsider. Roses attract no native insects. Mountain laurel does, it is much lovelier, can grow in partial shade, is evergreen, and so much easier to care for, requiring no pesticides like fragile roses typically do.
Witch hazel, you probably know, is famous for its exceptional properties as a natural astringent. We covered this shrub in a previous column in the November 2015 issue because it has a remarkable behavior not seen in almost any other plant: it flowers in winter (only the native witch hazel does this—the imported Chinese or Japanese witch hazel flowers in spring). What better way to add mystery and diversity to your garden than to plant witch hazel? This is a marvelous shrub that in late November sports bright thin yellow petals that stand out against snow and dark grey skies. It is pollinated by tough all-weather flies, bees, moths, and even beetles that venture out in the late fall and early winter. And laying their eggs on the witch hazel are the beautiful striped hairstreak and harvester butterflies, as well as the witches hat aphid.
Mapleleaf viburnum is so named because the paired opposite leaves resemble the leaves of maples, just like a gardener’s favorite, oakleaf viburnum, and has foliage resembling that of white oaks. The mapleleaf viburnum doesn’t receive the same attention as other viburnums, a number of which are planted in local gardens and are not native. Yet its fall fruits attract white-throated sparrows, cardinals, and other birds. Its delicate white flowers are my favorite among the viburnums. But the mapleleaf viburnum earns a first prize among all of our native shrubs: most beautiful fall foliage. In autumn, the leaves of mapleleaf viburnum turn exquisite hues from purple to blue or magenta. When the afternoon sun backlights this viburnum, it is one of the visual pleasures of my early November walks along the creek. Just as the mountain laurel can sub for rose bushes, the mapleleaf viburnum can take the place of the invasive burning bush planted so frequently in our neighborhood. Do the eye test from the images on the internet for fall foliage and watch your preference shift to the native.
And the runner-up for the most beautiful fall foliage? I offer witch hazel. Unlike mapleleaf viburnum, which is a solid purple, witch hazel leaves can come in shades of purple, yellow, red, or orange, on single leaves or all on the same leaf. It is a blaze of fall color condensed to a single bush.
Set against the cheery evergreen foliage of the mountain laurel you have several gorgeous native shrubs that give pleasure over the seasons, require no care once planted, and will prosper for decades. Better still, you can purchase these plants online or at local nurseries like Nature by Design in Alexandria, where I bought most of my native plants. And, in this era of COVID-19 and home delivery, Nature by Design brings plants to your door. Go to www.nature-by-design.com to find these three stalwart shrubs and virtually all of the natives that I’ll write about and Trudy will illustrate in this year’s columns. Late February or March is an excellent time to put them in the ground.
We are lucky to be living so close to wilderness. And with the addition of these three plants, we can bring a parcel of wilderness right into our yards.
ERIC DINERSTEIN , Contributing Writer
ILLUSTRATION BY TRUDY NICHOLSON