English ivy, creeping up a brick wall or climbing the trunk of an old tree, evokes an atmosphere of stately age and established beauty. In the eyes of an experienced gardener, however, the atmosphere is filled with concern and hard work. Left to its own devices, this European ornamental has transformed into an invasive problem on both US coasts, suffocating and eventually killing trees with out-of-control growth. English ivy is no longer a landscaping problem-solver. On the contrary, it has become a problem to be solved.
As is the case with many plants now regarded as American natives, English ivy surely travelled in cuttings and seeds along with early English immigrants. Looking at English gardens over the centuries, one notices a number of common elements transcending styles, and it is understandable that, to English people of many classes, common ivy was a touch of home.
Geography and Climate
Clearly, temperate growing conditions on both US coasts have made it easy for English ivy to grow out of bounds. It has now assumed the proportions of an invasive weed from Pennsylvania south to Georgia on the East Coast and from Washington to California on the West. Reasons for its excessive flourishing are varied but one can speculate that warmer and sunnier conditions than those found in the British Isles have played a part.
Perhaps the attribute contributing most to the overwhelming growth of English ivy is its appearance. Ivy does not have either the unattractive appearance of many weeds nor their destructive reputations. Gardeners are often likely to spare ivy when clearing other weeds--the popular opinion that it's "only ivy" can result in miles of unanticipated growth.
English ivy's exuberant growth damages trees by literally suffocating their growth. Often appreciated as a weed-choking ground cover, ivy does not discriminate between wanted and unwanted plants. Close, strong growth covers trees to the point of impairing new branch, bud and leaf formation, necessary for the tree's survival. Branches weaken and die as light and water are shut out by the ivy blanket.
No matter how pretty it is, English ivy must be removed and kept away from tree trunks. One set of communities points out foresters' concerns that ivy growth increases potential fire damage as well as possessing other health effects. In the absence of fire danger, ivy removal is still an important project. Gardeners remove long shoots by cutting ivy-free rings around trees, pulling, and digging out roots on an ongoing basis. US native vines and creepers can be planted instead of English ivy, or trees can be allowed to flourish bare. Ironically, removing the vine that gives trees an air of dignified age may be the best strategy for allowing those trees to live long and healthy.