Perennial Vines: Friend or Foe?

Perennial vines have many uses in landscaping. Some support a variety of wildlife. Virginia creeper (Parthenocissus quinquefolia) is the host plant for the larvae of the Virginia creeper sphinx moth, the Achemon sphinx moth, and the grapeleaf skeletonizer. Birds eat mature dark purple or blackberries. Dutchman's pipe vine (Aristolochia macrophylla) is the host plant for the pipevine swallowtail butterfly. Hardy passionflower (Passiflora incarnata) is a favorite of bumblebees in particular. Also called maypop, hardy passionflower produces fruit that is edible by humans. American wisteria (Wisteria frutescens) attracts butterflies and is a larval host to several species of butterflies and skippers. Trumpet vine (Campsis radicans) is used by hummingbirds as well as insect pollinators. American bittersweet (Celastrus scandens) is a good food plant for birds when the berries ripen to brilliant orange after a freeze in the fall.

Many of these vines also have attractive or unusual flowers. Most of us would recognize the grape-like cascading clusters of lavender flowers of wisteria, some of which are scented. Trumpet vine flowers are available in a variety of colors, from yellow to orange to red. Passionflower's unique shape with protruding parts is especially eye-catching. The flowers can vary in shape from shallow saucers to long cylindrical to a trumpet-like tube. No matter which forms, the blossom consists of five sepals on its upper border, five petals, and the most conspicuous of the flower, the corona, consisting of membranous outgrowths. The stalk emerges from a middle ring of five stamens, which produce abundant pollen. Three styles above the stamens contain the ovaries, which each end in a stigma. The flowers are also nicely scented when they first open, but after a day, the scent deteriorates into a faintly rotted odor. Dutchman's pipe vine has small, pipe-shaped reddish and green flowers that are hidden under the leaves; they have to be searched for in the spring but are a delight when found.

Perennial vines can cover problem spots in the yard, hiding an unattractive fence or view. They can make a good and natural screen between neighbors or properties. They can provide shade, especially when covering a pergola or arbor. Wisteria, a legume, fixes nitrogen in the soil. The extensive, deep root systems improve the quality of the soil and require less water than shallow-rooted plants.

However, perennial vines also have serious drawbacks. The most obvious is their tremendous ability to spread on underground stems, rhizomes, or root stalks. A vine planted here can pop up over there and can be difficult to control or eradicate. Perennial vines can encroach on native areas and squeeze out native plants. Introduced invasive vines, such as Oriental bittersweet (Celastrus orbiculatus) and Japanese (Wisteria floribunda), and Chinese wisteria (W. sinensis), can cross-pollinate with native American bittersweet and American wisteria, thereby negating their effectiveness in supporting native pollinators. Climbing vines planted along foundations can damage the mortar in brick houses as the tendrils cling to the building, and tendrils can even work their way under vinyl siding, loosening and damaging the siding.

Some perennial vines, despite being attractive to pollinators, are troublesome or dangerous to humans and pets. Virginia creeper can irritate the skin if contact with the sap occurs. All parts of Dutchman's pipe vine are toxic if ingested; even the bark should be avoided. Japanese and Chinese wisteria species produce attractive, fuzzy seed pods, but the seeds are poisonous. American bittersweet is not toxic and has been used for centuries by Native Americans, but the introduced Oriental species have poisonous berries that can cause nausea, vomiting, and diarrhea if eaten by humans or pets.

Perennial vines can be kept under control with yearly pruning and diligent observation for tendrils emerging in unwanted places. But when they become problematic, eradicating them can be difficult. Cutting them back to a couple of inches from the ground and then carefully applying herbicide is one solution, and this may need to be done more than once. Attempting to dig them out is another possibility, but getting all of the root systems is challenging and likely can't be accomplished in one session. Emerging stems in other parts of the landscape can be mowed over; repeated mowing might kill them.

Weigh the pros and cons carefully before planting perennial vines. As long as the vines can be kept under control by the homeowner, they may make a wonderful addition to the home landscape.