The GARDENA gardening expert
Dear Mr. S., the ivy will cause little to only minor damage to your tree. First of all, the ivy only makes use of the tree as a climbing frame, and is not a parasite like mistletoe, for example. This means that the ivy roots do not penerate into the tree and remove any nutrients.
However, the following can happen:
1. After all these years, the ivy achieves a significant weight. Therefore, your apple tree should have had a classic crown growth with well-formed, powerful bearing branches, in order for it to carry the weight of the ivy even during wet weather or under snow. In general, it should cause no problems. However, branches will break if they become rotten.
2. It is important not to let the ivy climb out over the roof canopy of the apple tree. Only when the ivy cuts the leaves of the apple tree off from the light does a competition arise between the two plants.
As long as the ivy's position does not damage the tree, which seldom happens, we can consider the interaction of the two plants as an ecological enrichment. The roof canopy provides sanctuary for numerous insects and nesting places for birds. In addition, the ivy flowers in late autumn provide bees with an extra source of nectar, and blackbirds love to eat the mature fruit of old ivy when times are hard in late winter. These green oases of rest in winter, when most other plants lose their leaves, are also pleasant for us to look at.