Ivy – love it or hate it- TreeAbility – The tree professional’s opinion of ivy on trees
Ivy is a very divisive subject, here are what I feel, as a professional Arborist, are the pertinent points in favour and against ivy on trees. I draw these conclusions after almost 10 years in the arboriculture industry and now as owner of TreeAbility.
If you are a fan of ivy then sorry to disappoint but there is only one actual benefit of ivy on trees; It provides habitat for wildlife. This can be in the form of shelter for nesting or hibernating and foraging for birds and insects. As ground cover it has value for preventing frost, enabling birds and animals to find food during winter and again providing habitat for animals and insects. But I digress, it’s ivy on trees we’re talking about!
Ivy infestation causes huge problems for trees and the safe management of them. Visual tree assessment (VTA) is severely hampered by ivy. This is an essential part of exercising your duty of care to the public when you have trees near public access and other peoples property. Your duty of care is exercised by having a professional Arborist periodically carry out a VTA of your trees. This is a visual check for any signs of problems with the trees. Fungal fruiting bodies, cracks, cavities and other tree diseases and defects are almost impossible to spot through ivy so it is very easy to miss such problems.
Wind loading is another problem with ivy on trees. Deciduous trees lose their leaves in winter to help prevent them being buffeted by winter storms and gales. Ivy is evergreen and thus gives the tree a full canopy of leaves even during winter. This causes a lot of branch snap within trees and wind blow of whole trees where they are blown over. This is exacerbated by wet ground as the soil around the tree loses its cohesion and the whole tree and root plate lift out of the ground.
The physical weight of ivy on trees also causes problems. When swamping a whole tree it almost doubles the weight of the tree. This again causes branch snap and pulls trees over.
Light levels to property and gardens are badly affected by ivy on trees as well. This is even more noticeable in winter when deciduous trees are leafless and light should flood through bare branches. Ivy blocks out huge amounts of light and the removal can transform a garden or house which had previously been overshadowed.
Aesthetically, ivy spoils the natural beauty of trees and prevents you seeing the trunk and branch structure.
On a professional level, ivy makes tree work a lot harder and more dangerous. A lot of the tree surgery accidents I have seen over the years have involved cutting in ivy. It can snag the saw causing kickback and make seeing ropes and equipment difficult when cutting.
How to control ivy
There are two main methods of dealing with ivy on trees:
Complete removal from the tree. This involves climbing the tree and cutting and pulling all the ivy out of the canopy. It is time consuming but well worthwhile as it sorts the problem and allows immediate VTA to check for any problems with the tree.
Secondly, girdling or severing the ivy near the base of the tree. This is the removal of a band of ivy round the whole of the trunk of the tree. This kills the ivy above the cuts. The ivy then dies off and the leaves will fall off. Eventually the stems go brittle and can be pulled out but this can take many years. VTA is possible once the leaves fall off and the root flare of the tree can be assessed immediately the ivy band is removed at the base however it is not as effective as complete removal of the ivy.
Ivy’s waxy leaves make it very difficult to spray herbicide on it to kill it. It can however be applied directly to the cut stems when removing or girdling it. This is the most effective method of killing the roots of the ivy and has no negative impact on other flora. Spraying needs to be repeated several times and is indiscriminate on what it will kill if it hits other flora so I would not generally advise that approach.
If you are an ivy lover then I would recommend only letting ivy grow on the trunk of the tree. Do not let it creep into the branches and crown when a lot of the problems listed above become more serious.