Newcomers to Charleston frequently lament that, in spite of its beauty, the Lowcountry lacks spectacular fall color. The thing is, heart-stopping Technicolor does exist here, but our autumn shades consist of subtle layers of innuendo instead of endless masses of vibrant colors. Sure, there are brief glimpses of bright orange, red and yellow, thanks to ornamental trees, like crape myrtle, dogwood and Chinese pistache (Pistacia chinensis). Even our ubiquitous native vine, Virginia creeper, tries to brighten up the landscape by turning Day-Glo burgundy sometime around late summer.
However, the finest autumnal thrills occur in and along our zillions of acres of wetlands— where marsh grasses slowly turn from vibrant lime and kelly green to seemingly endless ribbons of shimmering gold at summer’s end. Set against a Carolina-blue sky on a crisp, cloudless day, it doesn’t get much better than this. Except it does.
Sometime in early August, mostly along rivers and streams, sweetgrass (Muhlenbergia spp.) begins to turn from ho-hum green to delicate pinkish-purple. By the end of September, it’s deepened to an indescribable ethereal mauve. For those seeking a botanical thrill, drive—or better yet— walk the quarter-mile slow bend along Lockwood Boulevard beginning near the City Marina and east toward the Coast Guard Station on Charleston’s peninsula. Snugged between the sidewalk and the riprap at the edge of the Ashley River is a nearly continuous band of lush sweetgrass. The best time to do this is in early morning when the sun sends flickering, twinkling light through downy tufts of iridescent lavender.
Botanically speaking, those tufts are hair-like flowering structures called awns, and they give sweetgrass its floatingcloud effect. While over 150 species of Muhlenbergia exist, our native one inhabits sparse, narrow bands of dune lines from North Carolina through Florida. Although more abundant in the Sunshine State than here, sweetgrass “belongs” to us because of its profound cultural and historical influences on the Lowcountry. While other native plants such as Magnolia grandiflora and Spanish mossdraped live oak define the Deep South’s sense of place, no other plant in our landscape repertoire defines us better than sweetgrass.
This is because it recalls our agrarian story about abduction and human bondage. Sweetgrass was first gathered by enslaved Africans to make coiled basketry for harvesting their masters’ rice. But even then, more than 300 years ago, the artistry in a sweetgrass basket far exceeded its utilitarian purpose.
Sweetgrass, which is horticulturally classified as an ornamental grass, has become a popular choice for home landscapes. Like other ornamental grasses, it lends texture as well as color to an overall garden design. The problem with sweetgrass is that we either don’t understand its needs or refuse to pay attention to them.
In the wild, sweetgrass is found in open areas, thriving under all-day sun along banks and ditches where moisture is plentiful. However, our demand for it has persuaded nurserymen to enhance its biological adaptability. As a result, some varieties are less moisture dependent than straight species and a few, such as Regal Mist Pink Muhly Grass (M. capillaris ‘Lenca’), grow in partial shade (3 to 5 hours of direct sunlight) to full sun (6 to 8 hours of uninterrupted sunlight). However, it has been my observation that when sweetgrass is planted in less than full sun, it’s often impossible to coax it into its full fall color. But before throwing in the trowel over disappointing performance, be sure to also test the soil. Given that the wild species can’t survive in low pH soils, there’s no reason to assume that cultivated varieties are different.
Also, keep in mind that no drama exists when two lonely clumps of sweetgrass sit side by side. Sure, a few interspersed in an herbaceous border add interest, but because their flower heads are finely textured, mass plantings are needed to create a stunning effect.
Because nurserymen have also tweaked and diddled with the overall height and width of sweetgrass, in general, a clump reaches a mature height of about 2 feet. Expect it to spread somewhere between 1 to 2 feet. The best assurance for proper spacing, and an important requirement for a spectacular outcome, is to heed the growing information on the label.
There’s also something about many sweetgrass labels that could confuse an astute gardener who’s as interested in botany as horticulture. Although scientists cringe at the thought of assigning one species name to three different plants with similar yet slightly different characteristics, plantsmen have done just that. I consider this a matter of necessity and an intelligent attempt at consistency within the commercial plant trade. Here’s the scientific side of the story:
André Michaux (1746 – 1802), the Lowcountry’s revered French botanist, gave sweetgrass its first scientific species name, sericea. But once slight differences in awn structure were discovered, additional appellations were handed out. Botanists ended up with three names: Michaux’s plus capillaris and filipes. Although scientists continue to debate sweetgrass species designations, when purchased from a reputable source, gardeners may rest assured that if a plant tag says M. capillaris, it’s sweetgrass. Take as many as you can possibly carry home with you.
PJ Gartin is a freelance garden writer who lives in Charleston.