Does ivy kill trees?

19 March 2020 6 minute read

Could Ivy be the most misunderstood kid on the block?

Have you ever been worried by ivy? Have you looked at a tree that seems smothered by it and thought the tree needs rescuing? You’re not alone. Swathes of ivy on bare trees are even more conspicuous over winter and at this time of year. It looks as if trees are being choked by an encroaching blanket of green. A common assumption is that ivy kills trees. You can breathe a sigh of relief. Chances are the ivy you’re looking at is not doing any harm. 

Ivy has been miscast in the role of villain for years, but in the ancient past it was a hero. Even professional gardeners believed that ivy damages trees and buildings. But there is little scientific evidence for this. Only the roots attached to the ground have penetrative qualities which is how it gets nutrients from the earth. It’s not a parasite so it doesn’t need to delve into the tree itself, it just needs a prop to climb up. At the end of the day it’s not in ivy’s best interests to damage the helpful host. The aerial roots are only used as a support and don’t damage the bark. A healthy tree will not be affected and a tree looking worse for wear is likely to have been in a bad condition to start with. One thing ivy can do is compete for nutrients in the soil with the tree, but healthy mature trees can cope with that. In fact, ivy is really important for wildlife, providing essential habitat, food and protection especially in the winter.

On occasion ivy can have a negative impact on a healthy tree. It can reduce the tree's capacity to produce energy. If ivy climbs through a tree's canopy to the top, it can smother the leafing branches, which might limit the tree's ability to photosynthesise and get enough food. Even this is on its own is usually not enough to kill a tree. But trees that are vulnerable through disease, rot and age may suffer and be more likely to topple over in strong winds.

Many organisations such as English Heritage, National Trust and the Wildlife Trusts have spent time looking at the evidence and carrying out their own research to decide on what their approach should be. It seems that most of the time ivy is helpful for wildlife and in the right conditions it can protect old structures from the elements. But there are certain instances when it can cause damage to manmade structures and may not be a good idea. So a more nuanced approach is needed, to make an informed decision about when to keep and when to remove ivy. 

When it comes to wildlife it’s clear that ivy is a friend. The yellow green flowers come out late in the year, September into autumn. They provide a lifeline of nectar for insects at a time when there are few flowers. Its beneficiaries include honeybees and red admiral butterflies. The Ivy bee has even shaped its whole life cycle around ivy. It emerges between September and November, to fit in with ivy’s flowering period, a time when other bees are finishing up for the year. The blue-black berries mature through winter which many birds enjoy and the high fat content helps them to survive into spring. Thick clumps of ivy provide a cosy home for bats, birds and insects. 

So what about ivy’s past fame?

The ancients admired it, associating it with the Greek god Bacchus who morphed into the Roman god Dionysus. He was the god of wine, fertility, theatre, cultivation and revelry. Unsurprisingly a popular god. And only ivy was good enough to be his crown. It seemed fitting, being an evergreen and perhaps because folk thought it prevented drunkenness. Ivy became a leafy symbol of achievement and wreaths crowned winners of poetry contests in Rome and winning athletes in Greece. 

Closer to home, in pagan times ivy must have seemed miraculous, staying bright green throughout bleak harsh winters. Along with holly, it was used to decorate the inside of homes. Cheery verdant leaves, a sign of life during the dark times and a reminder of the spring to come. A pre-Christian pagan tradition that carried on despite at one point being banned by the council of churches. 

You can’t keep a good ivy down! It went on to become firmly embedded within Christmas and other Christian traditions. A bit of this jolly spirit took the shape of carols. Ivy came to symbolise women while holly symbolised men and this combination lead to many carols that debated the merits of men and women in a good-natured competition. A pruned remnant still survives, the holly and the ivy is still familiar to many folk, though now all mention of the ivy apart from the one line, has been lost.

Ivy was also regarded as a symbol of fidelity maybe because of the way it can bind different plants together. This was adopted by later Christians, priests would present a wreath of ivy to newly married couples. Some bridal bouquets still contain a sprig of ivy. As well as love and friendship ivy went on to be associated with immortality and death. It is often seen carved on Christian tombs and was once placed on the graves of the dead on All Soul's Day.

From such ancient and rowdy beginnings Ivy has been on quite a mythological journey. From hero to villain. It’s time to reinstate it as one of the good guys. It has earned its place to be part of our woodlands, time for it to be celebrated again. Next time you come across a bit of ivy enjoy the jolly greenery draped around a bare tree. Remember the gifts it will provide for the wildlife around it and raise a glass to this ancient symbol of life. 

Further reading:


Donate to Trees for Cities and together we can help cities grow into greener, cleaner and healthier places for people to live and work worldwide.