Over the years, it is a shrub I get asked about a lot; and I spend quite a bit of time dispelling myths about the alleged harm ivy can do to trees and walls.
So I thought I would add my own festive celebration of this often under-appreciated woody climber.
Busting the Myths
Ivy has aerial roots that it uses to climb with, these do not absorb nutrients or 'attack' trees or brickwork. Recent Oxford research concluded that ivy generally does more good than harm, even on old buildings. From my own experience, I tend to agree that certainly on walls pointed with modern cement based mortar, ivy rarely causes any issues On trees it is more of an epiphyte, and not a parasite; it uses the tree as a means to climb high and reach sunnier parts of the woodland. It takes it's nutrients and moisture from the soil; cut the ivy's main stem and it will die back.
Benefits of Ivy
- On buildings, ivy can act as a climate moderator, insulating from the cold in winter and from overheating in the summer.
- In many cases, it can protect brickwork from erosion.
- It flowers very late (Sept to Dec) and it's pollen is an important food source for insects that wake up during warm spells of weather during the winter.
- It provides evergreen colour during the dark days of winter.
- More importantly for wildlife, the evergreen nature provides roost and nest sites for birds, bats and other small mammals, butterflies and other overwintering insects.
- It's seeds appear throughout the winter and provide food for a birds. They are poisonous to people though, so don't be tempted to try them!
- Very good plant for softening off hard landscaping features, particularly in shady areas.
- Grows in most soils.
- Available in a range of variegated forms.
When to Control Ivy
There are situations where ivy may need to be controlled:
- On trees and hedges, when ivy reaches a certain mass, it will block out sunlight and and add extra weight to the tree. In the winter, this, coupled with the 'sail effect' of the evergreen leaves, can be enough to bring down a weak tree in high winds. The shading alone can be enough to kill an old hawthorn hedge.
- On walls, despite the research above, I have seen cases, where the stems were very heavy and the mortar was old, when the weight had brought a sheet of ivy off the wall, damaging brickwork along the way.
- In the right circumstances, usually in non-ancient or secondary woodland, ivy can become dominant, block out light and prevent other species from establishing.
How to Control Ivy
The best way is to manage the ivy is by cutting back. Using a pruning saw, cut completely through the ivy's stem in two places so that a chunk of stem about 75mm long is removed. This will kill off any part the plant being fed by this stem. Doing this allows the ivy to slowly die back, preventing too much disturbance to anything living in branch structure. Avoid pulling stems off walls and trees to prevent loose bricks or dead wood hitting you on the head.
Removing the root of the shrub from below the cut stem will prevent it from regrowing.
For a simple solution, or for more free advice, call Northumbria Land Management 07910 22 33 34.
Northumbria Land Management
The article above has been written for education and guidance purposes. It is assumed that anyone undertaking the practical procedure described will have reasonable gardening experience, will be aware of site specific risks and work within their own limitations.