English Ivy's Adverse Impacts on Trees
Ivy competes with the trees, especially seedlings, for water and nutrients.
Ivy vines eventually grow into a dense cover on the bark of the tree's trunk. depriving the bark of the normal contact with air and micro-organisms.
Ivy vines grow to a very large size - often four or more inches in 30 or less years - and have a very high water content thus add considerable weight to the tree making it more susceptible to toppling and blow-down.
The stiff, waxy characteristics of Ivy leaves hold water, ice, and snow which also add to weight and exacerbate conditions leading to toppling and blow-down.
Mature Ivy grows in spiral pattern as opposed to the horizontal-vertical pattern of the immature plant thus it 'furls' out around the branches and trunk further reducing the ability of the tree to perform photo-synthesis.
When Ivy grows up the tree seeking the light it needs to mature and propagate, it eventually covers the apical stem or apex of the tree. The tree reacts as if it has been topped: experiencing biologic stress and sending messages of its distress out to the types of micro-organisms whose purpose is to hasten the demise of the tree.
The Ivy growing around the tree has supplanted the deciduous plants which have a growth and decay cycle that replenishes the nutrients in the soil.