Ivy - Stop the Chop

Round our way over recent months there has been a scourge of cutting the trunks and stems of ivy climbing up trees. We are not sure who is doing it, but it is at best misguided and, more truthfully, ecological vandalism. These two photos show recently cut ivy stems and the dead ivy now in the tree. Fortunately, ivy is a determined plant, and new young shoots are finding their way up the trunk from the base, but that is not the point. 

When I was a boy, there was a mistaken belief that ivy was some kind of parasite and that it harmed trees, so people went around cutting every ivy stem they could find growing up a tree. As education about this wonderful native evergreen spread, attacks on it subsided but suddenly there has been a resurrection of this environmentally harmful action, perhaps because botany and plant sciences have  been dropped from school curricula. I will explain why this stem chopping is so damaging to nature in a minute, but firstly, please understand that I am not saying ivy should be allowed on every tree it creeps up on. There are, of course, specimen horticultural trees where ivy would detract from their form and even contribute to their falling fall in gales, and occasionally very thick ivy on avenue trees along roads can obstruct safe traffic visibility – but as a general rule, the benefits of ivy ecologically far outweigh any downsides.

Ivy flowers are an important source of late season nectar. My photo shows the flower umbels which are about 4 or 5cm across, and embryonic fruit. The ripe berries (inset) are each about 7mm wide and contain up to five seeds; they are consumed by many birds which distribute the seeds in their droppings.

Before looking at the advantages of this plant, we need a little botany. Our native species is Hedera helix Linnaeus, 1753. It is an evergreen woody climber with an interesting life history: it can climb to at least 30m but also cover the ground where there is nothing to climb. Mature plants, usually when they reach good sunlight, produce flowering stems with cordate (heart-shaped) leaves rather than the palmate, five-lobed leaves of the younger climbing/creeping growth stage. It is an epiphyte not a parasite, only growing up trees and other support-providing structures by means of small, tightly-gripping aerial roots, and towards the light where it can flower and fruit, but it takes no nourishment from the supporting substratum. When trees covered with thick ivy eventually die or become frail in old age, the ivy’s weight may be a factor in toppling them, but that is part of nature’s cycle. Ivy grows in most soils but dislikes hot, sunny situations where it can suffer from desiccation; it is quite happy on a north wall or shady rock face, and of course in moist woods.

Here are some ecological and landscape benefits of ivy:

• Blossoms provide late-season (autumn) nectar – over seventy species of macro-invertebrates are known to feed on them;
• The fruits, though somewhat poisonous to humans, are food for at least sixteen bird species;
• Ivy provides excellent nest and roost sites for birds, roosts for bats, and shelter for many other animals;
• On houses and other buildings as an attractive “green wall”, an ivy covering helps keep warmth in during the winter;
• In summer, ivy on a building helps keep it cool (best to keep it out of gutters and away from unsound brickwork though!);
• An ivy covering helps protect structures from soil moisture;
• It can be useful ground cover for shady areas or to cover unsightly landscape features. 

I therefore get cross when I see people going round cutting ivy stems growing up trees unless the tree is of some special specimen value. Please don’t do it.

Betts Ecology always retain ivy on trees unless there is a clear and pressing safety issue, and we instruct our arboriculturalists to do the same. If we find that third parties are cutting ivy stems on our sites, we will act to stop them and explain why it is not good practice. 

 © Betts Ecology