Gelsemium sempervirens aka Carolina Jasmine

Gelsemium sempervirens, or Carolina jessamine, is a woody climbing vine. It belongs to the Gelsemiaceae family and stays green year-round. Its native range runs from the southeastern United States to Honduras. This includes Mexico and Guatemala. Wild plants grow in woods, thickets, and coastal sites. South Carolina chose it as its state flower in 1924.

Garden plants climb about 10–20 feet [3–6.1 metres] high. They may spread 20–30 feet [6.1–9.1 metres] across. RHS gives a smaller height of 8–13 feet [2.5–4 metres]. Its spread estimate is 1.6–3.3 feet [0.5–1 metre]. Thin, wiry stems twist around trees, fences, and supports. Without support, the plant forms a bushy ground cover. Brown or reddish bark gains cracks with age. Glossy, narrow leaves grow in pairs along the stems. Their edges are smooth, and each leaf has one blade. Winter can turn the leaves bronze, yellow, or purple. Plants may lose some leaves near their northern limits.

Yellow, scented flowers open from February to May, depending on place. Some plants flower again in fall. The funnel-shaped blooms grow alone or in small groups. Orange marks the inside of each flower's throat. Insects pollinate the flowers, which also draw butterflies and hummingbirds. Yet the pollen can harm honeybees and their colonies. Flat seed capsules appear from September to November. These turn from green to brown and split when ripe.

Full sun gives the strongest growth and best flower display. The vine also grows in light shade. It prefers moist soil that drains well and contains organic matter. It grows in clay, loam, sand, and chalk. Brief dry spells and some salt exposure cause little trouble. Sources list USDA zones 7–10 and UK hardiness H3. In Britain, outdoor sites need mild weather and wind shelter. Glasshouse plants need less water during winter. Prune after flowering to shape growth and guide the stems.

Use it on trellises, arbors, fences, or porch posts. It also covers slopes and trails from pots. Dense growth gives wildlife shelter from cold and harsh weather. It can become weedy beside roads and in disturbed ground. Its high fire risk limits planting close to homes. Serious pests and diseases are rare, though glasshouse whitefly can occur. Every part is poisonous; people and animals can suffer harm. It has no known food use. Sources record medicinal root use, but poisoning can be fatal. Wear gloves when handling it, since skin reactions can occur.