Plant Native and Avoid Invasives

By Susan Camp

My friend Cathy, who lives in eastern North Carolina, recently shared a photo of a huge, lushly beautiful Japanese wisteria (Wisteria floribunda) tree, the ground around it covered in lavender blossoms. You could almost smell the sweet fragrance. Cathy said she wishes she could have wisteria at her new house, as she had in Virginia, but since wisteria is non-native and invasive she won’t plant another one.

I have good news for Cathy. A native wisteria (also spelled wistaria) exists: American or Atlantic wisteria (Wisteria frutescens). Unlike Japanese and Chinese wisteria (Wisteria sinensis), the American species is much less aggressive, although vines can grow to 15 to 40 feet in length. American wisteria will need regular pruning to maintain an attractive shape and control its size, but it will not consume your trees, pergola, or garage.

American wisteria is a woody, deciduous, counterclockwise-twining vine, found in swampy woods and along stream banks in the southeastern United States from Virginia, south to Florida and west to Illinois and Texas. Kentucky wisteria (Wisteria frutescens var. macrostachya), a distinctive variety with more intense fragrance than American wisteria, also grows throughout the southeast. It may be classified as a separate species, depending on the source.

Wisteria species perform well in USDA Hardiness Zones 5 to 9. They prefer well-drained, moist, acidic, moderately fertile soil in full sun to light shade. Flowering may decrease if grown in shaded areas. Unfortunately, wisterias don’t like to be transplanted, so consider the size and amount of greenery surrounding the spot you choose for planting to ensure they will get plenty of sunlight for years to come. Wisteria can be trained to grow as a tree.

Pea-like flower buds emerge just after the opposite pinnately compound leaves have begun to develop in the spring, opening into drooping clusters of lilac-purple to blue blossoms that range from 6 to 12 inches in length. Peak bloom occurs from April to June, with some rebloom possible later in the summer. That’s the good news. The bad news is that wisteria may not bloom for anywhere from 2 to 10 years after planting. A light application of a low-nitrogen, high phosphorus fertilizer might help hasten flowering. Flower fragrance is less intense than that of the Asian species and may be minimal in some varieties.

Flat, narrow, smooth pods develop after the flowers have faded. The 5 inch-long pods split open in the fall to drop large brown seeds. The pods, seeds, bark, and roots contain a toxic resin and a glycoside called Wisterin. Ingestion of these chemical substances can cause an unpleasant gastrointestinal disturbance that, if severe, can result in dehydration.

Most sources report that American and Kentucky wisteria may be affected by aphids, thrips, leaf miners, Japanese beetles, and the usual fungal suspects, but suffer from no serious diseases or insect pests; however, kudzu bugs, which feed on legumes, have been found on wisteria in some states. Wisteria is black walnut toxicity and deer resistant. The vine is a nectar source and host plant for long-tailed skippers, Zarucco Duskywing, and other butterflies.

Popular cultivars of American wisteria are ‘Alba’ and ‘Nivea’ with white blossoms; lavender- purple ‘Betty Mathews’; and ‘Amethyst Falls’, which produces lilac flowers at 2 to 3 years after planting. Kentucky wisteria cultivars include ‘Aunt Dee’ with light purple flowers and a light fragrance; ‘Blue Moon’, which has blue-purple flowers; and white-flowered ‘Clara Mack.’

Publications about this lovely native vine include NC State Extension entry “Wisteria frutescens”; the Lady Bird Johnson Wildflower Center Plant Database entry “Wisteria frutescens”; the Missouri Botanical Garden Plant Finder entry “Wisteria frutescens”; and the Morton Arboretum articles “American wisteria” and “Kentucky wisteria.”

Helpful resource guides with information on many species of native plants include “Native Plants for Southeast Virginia Including Hampton Roads Region” from the Virginia Coastal Zone Management Program; “Native Plants of the Northern Neck”; and “Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed”, available from the U.S. Fish and Wildlife Service.

January 31, 2019