Professor Buczacki is a horticultural expert, writer and former chair of Gardeners' Question Time
Will ivy growing up my trees cause any harm?
Stefan says: This is one of those troubling questions that arises at regular intervals. You say you were told years ago never to let ivy grow up trees, but it now seems there is a different view on this.
Ivy is a native climbing or scrambling evergreen plant. It commonly grows along the ground where it forms a dense, tangled carpet of tough, wiry stems on which you can easily trip when walking through woodland. When it reaches a vertical obstacle, however, such as a wall, fence or tree, it will climb, often to a great height, using a multitude of short climbing roots that arise along the stems. Only when it has reached the top of the obstacle do the small flowers and black fruits appear. It is these fruits that provide an important food source for many species of birds, while the dense vegetative growth offers cover for insects and other small creatures.
It's important, in the present context, to realise ivy is a self-clinging climber; it’s not parasitic in the way, for example, mistletoe is. Hence, when it’s climbing on a tree, it draws no nutrient from its host plant. The question of harm to the tree arises, therefore, in a physical way. If the tree is young and small, it may be smothered, its leaves shaded by those of the ivy and unable to function and photosynthesise properly.
As trees become taller, more robust and mature, however, and with the ivy growth largely confined to the trunk and woody branches, that is no longer a factor, but what then becomes significant is its bulk and weight. When there is extensive ivy growth in the crown, the tree will become inherently unstable and prone to damage and even to being blown over in winter gales.
My view is ivy should always be removed from small trees and shrubs but can be allowed relatively free rein on mature trees, provided it’s not allowed to take over a large part of the crown.
FOUR CLIMBERS FOR A WALL
With rich soil, plenty of water and initial support, Campsis radicans will attach to a sunny wall and flower profusely.
Early-flowering clematis tend to be more vigorous; perfect for growing up a large wall or fence.
This classic climber, doesn’t mind a sunny wall, but will thrive in dappled shade in well-drained soil.
Afragrant climber for a warm, sunny wall. It needs a strong support but is relatively easy to care for.
I don’t want weeds to take over our wildflower patch!
