No, we are not referring to the noxious, tri-leafed skin irritant that is the bane of campers. The ivy in question is not chemically poisonous. Yet in certain circumstances, it can be far more insidious than its caustic cousin.
English ivy (Hedera Helix) is a staple in many metro Atlanta landscapes. It is cheap, spreads quickly, has pretty leaves, stays green all winter and thrives in poor soil as well as shade. As such, it is valued as a groundcover where grass won’t grow and as erosion control on slopes. Many also use English ivy as an accent in container plantings.
Yet despite the fact that gardeners willingly plant it, English ivy is classified as an invasive pest. The problems begin when English ivy begins to climb trees and buildings. The plant uses adhesive aerial rootlets (called “holdfasts”) to attach itself to surfaces. And while ivy may look striking on a brick building, the glue produced by these rootlets actually helps to dissolve the mortar between the bricks. Additionally, the ivy traps debris and moisture, the decomposition of which also takes its toll on the mortar.
English ivy becomes truly troublesome when it decides to climb a tree. Contrary to popular belief, it does not “strangle” trees or harm the bark. English ivy does its damage by shading out the tree’s inner leaves, which the tree needs to produce food. A large amount of ivy in the tree also serves as a “sail,” which catches high winds and stresses the tree’s stability.
English ivy in the landscape should be diligently pulled off of, and given a wide berth around, treasured trees.
1000 Gardening Questions and Answers –the NY Times
The Practical Gardeners Encyclopedia