The number one risk vines pose to trees is that they grow in the canopy and crowd out photosynthesis by covering and killing the trees leaves. A second possible risk but not verified is that the vines compete with the tree's roots for elements like nitrogen. This would impact the trees ability to provide itself with the necessary nutrients for its maximum health and possibly stress it.

Do vines cause the bark to rot? Yes or no, depending on the type of vine. Many vines like poison ivy or Chinese wisteria do not sufficiently cover a trees trunk to cause rotting. However, English Ivy often becomes dense enough to completely cover the trunk - allowing water to build up in the aerial roots, and not dry out because it's evergreen leaves shade the trunk. Worse yet, the presence of vines like English Ivy can make it impossible to see if there is a problem with the trunk of a tree - potentially leaving a hazard unnoticed.

Can vines strangle a tree? Once again, this depends on the vine. Vines such as Japanese and Chinese Wisteria circle around the trunk and can strangle the tree. Other vines that grow straight up the trunk will not strangle the tree.

Can vines cause structural problems if they get in the canopy? The vines weigh down tree branches causing them to break. Broken branches provide opportunities for pathogens to enter the Trees. English Ivy is approximately 80% water so it becomes quite heavy as it grows throughout the trees. Steep slopes, wet soil, and heavy ivy oftentimes combine to topple numerous trees.

Are vines ugly? That is up to you. Tree bark is often one of the most distinguishing features -especially in winter. Certain vines obscure the bark, while others are hardly noticeable.

What other problems can vines in trees cause? Vines like English Ivy only set seed when they grow vertically. Once English Ivy sets seed, it is spread by birds, often to local forests, where it can strangle native vegetation and damage other trees.

If vines get in the canopy it is time to cut them back by removing a three foot section at the base of the tree separating the vines from their roots and their water source. Be careful not to damage the tree's bark. Don't try to remove vines higher than the 3 foot section – it may damage the bark as you pull the vine off, or you may inadvertently pull a dead limb from the tree.

For more info go to: http://www.nlreep.org/invasive_plants.htm