English Ivy found its way to America with the British immigrants way back when and subsequently hitched its way to our Coast in the westward migration! Not being native to our coastal environments, it has no natural enemies (i.e., animals, insects, fungi, diseases) here to keep it in check. As a result, it has gone completely wild! Ivy has found its favorite growing grounds to be close to the earth and in the shade. Like all green plants, it needs sun to be able to carry on photosynthesis which is the process of separating carbon from C02 in the air. It then uses that carbon to support more growth! Ivy vines have evolved to have the ability to climb vertical surfaces in search of sunlight.

If Ivy is growing in the shade of a tree, the logical vertical surface to climb is the tree’s trunk. A patch of Ivy can send multiple vines up a tree where they can proliferate and virtually cover the entire tree to the point that the tree’s leaves are completely blanketed from sunlight. If the tree is unable to photosynthesize, it will then weaken and be susceptible to various diseases and could likely die from the ivy infestation. 

Ivy vines can grow nearly as large as the tree trunk itself and are easily heavy enough to break large branches. Ivy can become thick enough to act as a sail and be blown over in a strong wind. Ivy has become a threat to many of our California native trees, most notably along our Napa River trail. 

Removing woody vines growing on trees should take first priority when tackling invasive vines. Be sure to positively identify every vine, because not all vines growing on trees are bad. Avoid cutting native vines, especially poison ivy or you’ll get a nasty rash! When you sever a vine on a tree, everything above that point will die, so there is no need to remove everything growing on the tree. Instead, focus on removing everything from chest height down. This allows you to see very clearly if you missed any vines.

Depending on how old the vine is, you will need to use hand pruners, or a pruning saw to cut the vines. When using a pruning saw, be careful not to saw into the tree itself. Cut a vine at chest height and pull/peel the vine down past the base of the tree. If the vine is thick, cut it down to the base of the tree. You can then either leave the stump (cut-and-leave) or treat the stump (cut-and-treat) with a high concentration (between 20-50%) glyphosate solution to prevent regrowth. If you treat the stump, exercise extreme caution. Do not get herbicide anywhere but on the stump or it could impact the health of your tree