Saturday, July 27, 2013 —
Visualize a 17th-century English country home with its manicured gardens and nearby outbuildings, and you'll likely imagine brick walls covered so completely in ivy that only the windows and entryways poke through the greenage.
Ivy, particularly English ivy (the species most often seen growing in our area), is a member of the aralia family and is native to Europe and western Asia. It can be a beautiful addition to any landscape and can provide excellent ornamentation to trees, fences and garden walls. Its lush aesthetic appeal can't be denied.
However, when left unchecked, it becomes an invader that can grow out of control almost virulently, can be extremely difficult to remove and can damage those same trees, buildings and fences on which it earlier looked so good.
In some cases, ivy can cause permanent displacement of native plant populations. As an aggressive invader, it can escape landscapes to overrun forest ecosystems. The Oregon Dept. of Agriculture has even gone so far as to ban the transport, sale or propagation of English ivy in Oregon, labeling it as an invasive, noxious weed that out-competes native plants.
When a tree fully or partially engulfed with ivy shows signs of distress, it is tempting to assume that the ivy is "strangling" the tree. While this may be a little simplistic, the ivy does often out-compete the tree for nutrients and resources, leading to the tree's death.
Ivy can harm otherwise healthy trees. Since ivy's leaf cover is so thorough, a complete covering of ivy can prohibit sunlight from reaching the tree, especially when the vine grows large enough to cover branches and the tree's own leaves. English ivy loves full sunlight and tends to keep growing up the tree in search of light. As the ivy climbs, it often begins to kill the leaves that it covers, resulting in the tree's death from the ground up.
Ivy on tree trunks often spreads out along the ground encircling the tree. The root structures of the ivy tends to draw out water and precious nutrients that would otherwise sustain the tree. This ivy around the base of a tree can shield the tree from water and also keep vital decaying plant matter off the ground.
When ivy has grown enough to cover an entire tree, the vines add a considerable amount of weight to the tree and, depending on the strength and health of the trunk, can present a danger to the tree. This is especially true during the winter months. As an evergreen, ivy remains on the tree in its entirety when the tree is at its most vulnerable state of hibernation. High winds and heavy snows and sleet can further add to the stress on the tree and make it much more likely to break or fall.
Also, when fully covering a tree, ivy can prevent leaf-out in some cases, eventually killing the tree.
The same traits that make English ivy a good ground and wall cover (fast growth, resiliency and its ability to cling) can also make it a difficult to remove. But if you decide to rid a tree of ivy, first, using garden clippers, cut the ivy at the bottom of the tree around the entire trunk. Then pull all the ivy vines out of the ground around the base, making a 2-foot ring around the tree. Once cut, leave the ivy on the tree. Pulling it off can damage the tree bark. Eventually, the ivy will die and dehydrate and you can either remove it from the tree then or just wait for it to disintegrate and rot away.
When removing it manually from the ground, ensure that you remove as much of the plant, both stems and roots, as possible because it can re-grow from stem and root pieces left in the ground.
When removing organic waste from any invasive plant species from your yard or property, always put it in plastic bags and in the trash. Never put it in the woods--even on the edge. Many invasive species can spread from even the tiniest sprig.
Alternatives to English ivy are trumpet creeper, Virginia creeper, passion flower vine and Dutchman's pipe.