Carolina Jessamine: Vine of the South

Carolina Jessamine: Vine of the South. Carolina Jessamine or the Vine of the South is commonly found in the Smoky Mountain region and is a great plant for the local landscape.                            

What is it?  Seen spilling over fences and arbors and trailing along woodland margins, the Carolina jessamine, state flower of South Carolina, may justifiably be called the vine of the South, for it is the most prominent ornamental vining plant cultivated in the Southeast that is also a native plant. It brightens gardens and landscapes with its intensely yellow trumpet-shaped flowers from late spring through the summer.  More widespread than its Asian transplant rivals, wisteria and clematis, it flourishes southward from Virginia to Florida and westward to east Texas, loving this region’s summer heat and humidity as well as its mild winters.  It is known by a variety of names—Carolina jasmine, evening trumpet flower, and woodbine—but the scientific name, gelsemium sempervirens, captures one of its most distinguishing and useful features:  its leaves are evergreen (i.e. sempervirens).  The gelsemium designation, however, indicates much less favorable trait:  the plant is toxic to human beings.

Where does it grow?  This plant is hardy in USDA zones 7-9 in the United States, but its range extends well into Central America.  It consists of strong twining bronze-colored stems that can reach upward or outward 20 feet or more with a spread of up to 8 feet.  Its deep green leaves are thin, lustrous, spear-shaped, and evergreen, although both the leaves and stems darken in color during the winter.  In the late spring the vine produces medium-sized trumpet –shaped flowers, rather like those of Asiatic lilies, which are intensely yellow and very fragrant.  Blooming continues until mid-summer when the plant begins to conserve energy to survive the drier, hotter months.  (Growers have also produced white, crimson, and pink flowered varieties.)  The plant’s strong deep root system adapts well to the heavy Southern clay soil, allowing the plant to tolerate the region’s hot, dry summers.  It also tolerates some shade but prefers full sun, except along the roots.

What is it used for?  Carolina jessamine is typically used as a climbing vine to decorate trellises, arbors, fences, and walls, but can serve as a hedge as well if supported.  Where no vertical support is available, it can also become an aggressive groundcover on sunny hillsides.  For gardeners who wish to feature native or historical plants, the Carolina jessamine is the perfect choice for a vertical highlight just as it has been in Southern gardens since the colonial period.

How to cultivate it.  Carolina jessamine can be grown readily from stem cuttings or seeds taken from existing plants.  Once the yellow flowers are spent, seed pods form in their place and gradually open to expose the seeds.  The pods can then be clipped from the vine and air-dried for several days to ensure the moisture is gone before storage.  (For storage, a small pouch made of aluminum foil works well. Once the seeds are enclosed, the pouch can then be placed in a plastic zip bag, the bag then labelled and stored.)  In late February the seeds can be started indoors in peat pots kept is a sunny spot and frequently watered before transplanting to the garden once the soil is thoroughly warmed, typically in May.  Care should be taken to shade and mulch the roots, however, as jessamine, like clematis, prefers its roots to be relatively cool.  Finally, the plant can be pruned throughout the growing season in order to improve its appearance and maintain its conformance to arbors, trellises, and pergolas.

Toxicity:  ALL PARTS OF CAROLINA JESSAMINE ARE TOXIC TO HUMAN BEINGS because it contains a substance known as gelsemine—a complex alkaloid related to strychnine.  The sap can cause minor skin irritation, so gardeners working with this plant should always wear gloves and long sleeves.  More importantly, children can easily mistake jessamine’s trumpet-like flowers for honeysuckle and poison themselves by ingesting the flowers or nectar.  This circumstance requires immediate medical care.  Butterflies and hummingbirds, however, are readily attracted to the plant and suffer no harm.

Unfortunately, the Carolina Jessamine’s toxicity is not limited to human beings.  It also appears to be toxic for the non-native honeybee, while not so for the bumblebee and other native osmia bees, which have learned to avoid it.  Honeybees ingesting the vine’s alkaloid nectar become disoriented and eventually die.  While Carolina jessamine is not a contributor to honeybee colony collapse, it is not a good ideal to locate bee hives near to it.

HeySmokies would like to welcome our new contributing writer Carl Parsons. Carl is Deputy Editor for Storyteller Magazine, a member of the Writers’ Guild of Sevier County, TN, and a Tennessee Master Gardener.