What is strong enough to climb 60 feet, can be 10 inches in diameter, cover a house, and kill trees, shrubs, and anything living standing its way? Would you believe vines? The three worst invasive vines in Western North Carolina are Japanese honeysuckle (Lonicera japonica), kudzu (Pueraria montana var. lobata), and Oriental bittersweet (Celastrus orbiculatus), according to the USDA National Agricultural Library, North Carolina Forest Service, and NC State University.
How did they get here and where are they now?
Good intentions gone bad! All three apparently arrived here during the 19th century as ornamental plant introductions from Japan.
Japanese honeysuckle grows from Michigan to Florida and from the east coast to California. This shade-tolerant, evergreen, woody vine has elliptically shaped, opposite leaves. Its white or pale-yellow flowers appear from April to August, and glossy black berries are seen from June to March. It forms evergreen mats that shade out other plants. It spreads by seeds, runners—stems that grow horizontally, rooting in the ground producing baby plants—and rhizomes—modified roots that grow horizontally just under the surface of the ground.
Kudzu ranges from New York to Texas and has made its way to Washington, Oregon, and Hawaii! Each leaf has 3 parts. The center leaflet has 3 lobes; the outer leaflets have 2 lobes each. Kudzu flowers from June to September, producing small lavender-to-purple, pea-like flowers that hang down in spikes, forming seed pods in the fall.
From 1935 through the early 1950s, the Soil Conservation Corps encouraged planting kudzu to help with soil erosion; roadside plantings proved particularly aggressive. Kudzu also grows in fields, disturbed forests, and forest edges, spreading through rhizomes and runners. Up to 100 feet in length, this deciduous woody vine can grow to 3 to 10 inches in diameter, killing other plants by growing over them.
Oriental bittersweet has made its way to all states east of the Mississippi and much of the Midwest. This shade-tolerant vine can reach 60 feet in length and get up to 4 inches in diameter. It kills other plants by strangling trunks and stems, blocking sunlight, and generally weighing down them down! Birds spread its seeds. If you gather or purchase dried stems of bright yellow-red berries for decorative use, you may be contributing to the spread of this invasive by helping the berries/seeds find their way into the landscape or landfill.
Native American bittersweet note:
Not all bittersweet is an invasive weed! American bittersweet (Celastrus scandens) produces flowers and berries at the end of the stem, while Oriental bittersweet has flowers, then berries, along the entire stem.
With these weeds, the best defense is an aggressive offense! Don’t give them a chance to grow—pull them up when you spot seedlings. For older vines, removal is much more labor intensive and may involve cutting back—late summer is a good time—pulling up much larger root systems, smothering, mowing, or all of these techniques.
Herbicides are effective only when applied at the right time of year and even then, may require multiple applications. Remember to always follow label directions and be aware that these products may affect nearby trees, shrubs, flowers, grass, and vegetables.
Other invasive vines
NC State University also names the following vines as invasive: Cypress vine morning glory (Ipomoea quamoclit), English ivy (Hedera helix), porcelain-berry (Ampelopsis brevipedunculata), sweet autumn virgins bower (Clematis terniflora), winter creeper (Euonymus fortunei), and Chinese and Japanese wisteria (Wisteria sinensis and Wisteria floribunda).
Article written by Kay Green, Extension Master GardenerSM Volunteer.
Invasive, Exotic Plants of the Southeast
by NC State Extension
American and Oriental Bittersweet Identification
by U. S. Geological Survey (USGS)
Additional removal methods:
Guide to Control Methods for 10 Common Western North Carolina Riparian Weeds
by RiverLink Volunteer Corinne M. Duncan
Surgical Crown Removal of Kudzu
by KOkudzu.com: “Knock Out Kudzu”