Kudzu: Kill It or It Kills

Ever since kudzu touched American shores, the parasitic vine has destroyed every form of plant life to which it has become attached. Kudzu may not have invaded your garden (let's pray that it hasn't), but from the Deep South to the mid-Atlantic states, this vine has done more to kill trees than disease and insects combined. Control really doesn't exist. Local governments lack the funds to control kudzu along highways, streets and parks. Once kudzu invades an area, it takes what amounts to a superhuman effort to eliminate it.

Some landscapers have confessed it's cheaper to chain saw down a tree than trying to destroy kudzu, and they're right.

A lot depends on a tree's height and where you live. If you live anywhere in the South, you know what everyone says about the vines: "kudzu owns the South." In some areas, kudzu is so dense it camouflages everything else because vines have killed everything else.

It seems like kudzu owns trees. Small trees below 15 feet seldom pose problems for homeowners because climbing vines can be pulled loose from tree trunks and destroyed. With tall trees, however, aged kudzu vines usually win out. Spraying kudzu leaves with a pesticide inevitably weakens the tree, even killing the tree later on. Only with an arborist climbing the tree and manually pruning away vines clinging to the trunk can a tree be saved and kudzu temporarily checked, but only for a time.

The mystery surrounding kudzu is easily explained.

First, kudzu isn't native to North America, only to China and Japan. Kudzu came to America 140 years ago (1876) when an exhibit from Japan at the Centennial Exposition in Philadelphia portrayed the vine as an ornamental asset. For a half-century, kudzu didn't go anywhere, but during the Great Depression of the 1930's, the government's Soil Conservation Service promoted planting vines to combat soil erosion in the Deep South. Before 1940 and World War II, the government paid incentives to farmers beyond the Deep South to plant kudzu for erosion control. Not until 1972 did the curse of kudzu emerge when the Department of Agriculture classify the vine as a weed.

Kudzu first surfaced in the mid-Atlantic area in 1940 in York County, Pennsylvania. On a commercial nursery they found kudzu starting to climb a container rhododendron that had been field grown by commercial growers in Georgia. Apparently, a kudzu seedpod happened to be in the soil when the rhododendron was removed from the field and placed in a container. It was only a matter of time before the pod germinated and the vine started to grow.

Horticulturally, kudzu is a legume (fixing nitrogen in the soil) just like black locust and redbud trees. But kudzu has its horticultural reputation as a parasite. While kudzu develops a vast network of roots over time (some roots spreading up to three and four feet in the soil), kudzu prefers to live off the nutrition produced by deciduous trees, even evergreens on occasion. Kudzu isn't choosy where it grows.

The plant survives best of all in semi-tropical environments, but it has acclimated itself to inhospitable areas where freezing temperatures routinely happen over the winter. Where soil temperatures normally reach -15 to -20 below zero (frost lines dropping to 16-24 inches), kudzu roots seldom survive.

With falling temperatures in autumn, kudzu drops its leaves, but the vines don't die. Vines live from one year to the next. When air temperatures rise in the spring, kudzu throws out its first leaves near its base. In ensuing weeks, foliage develops along the entire length of the vine.

Kudzu wastes no time parasitizing a tree. As vines climb a trunk, "aerial roots" develop along the vine and puncture the outer bark. Every few inches, aerial roots happen. They pierce the woody bark and penetrate the white "cambium layer" from which the tree gains its sustenance.

Two food channels are imbedded in cambium tissue. Every morning at sunrise, food and water are drawn vertically in hundreds of microscopic "xylem" (zi-lem) tubes to nurture growing cells throughout the tree. By mid-morning, the upward flow of plant minerals and moisture declines considerably. At sunset, the reverse occurs. Carbohydrates and other minerals produced and stored in tree leaves during the day are transported to roots via hundreds of microscopic "phloem" (floam) tubes in the cambium.

Aerial roots of kudzu vines imbed themselves in this cambium layer, feasting on the constant flow of nutrients ascending and descending throughout the growing season. Kudzu livens when springtime food and water start flowing in tree trunks; kudzu goes dormant when fall temperatures decline and trees drop their foliage.

Kudzu behaves like a shark in landscapes because it produces flowers. Kudzu is self-fertile, meaning male and female parts exist on its blossoms. On a healthy vine, dozens of white flowers develop in early autumn, with pale purple seedpods. These pods overwinter on the ground, breaking open the next spring to spread their seeds. Flowering usually occurs the first two weeks of October in the Washington, D.C. area, as early as August in southern states.

Kudzu Control

Local governments have a wealth of products to eliminate kudzu. Available only for licensed applicators are Tordon K, Tordon 101 and Veteran 720 (a combination of Dicamba and 2,4-D). For direct application to soil above Kudzu roots is "Spike," an 80 percent wettable powder produced by DowAgroSciences. Assuming a 10 by 10-foot (100 square foot) area for treatment, 4.25 to 6 grams of Spike would be dissolved in 4 gallons of water and applied to dry soil over the root bed to avoid runoff. A second application two years later would eliminate kudzu regrowth.