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Ivy: pest or protector?

Photo: Philip PreceyIvy

By Dyane Silvester

We are all familiar with ivy.

It grows over our dry stone walls and turns our houses into quaint cottages, we use it in wreaths and decorations at Christmas, it twines round our trees, choking them and competing for nutrients. Or does it? Is ivy a rampant pest damaging our environment, or simply a hardy climber providing shelter and food for our animals and wildlife?

Ivy grows quickly and easily and although the idea that it makes the bricks and mortar of your house crumble is a myth, if your masonry is already weathered or soft, ivy can speed the deterioration. On dry stonework, it will inveigle itself into the gaps between stones and as it grows bigger, prise the stones apart. As it climbs your timber fence or shed its suckers and branches will take advantage of gaps in the timber and induce or speed up rotting.

In the right environment however, we mustn't forget the positives of ivy; the shelter and food it provides for birds who feed on its berries (the ivy on my garden wall regularly has several feeding blackbirds in it); the pollen that bees and hoverflies seem to love. Indeed where ivy forms a ground cover it protects the area beneath from frost, providing an ideal place to hibernate, shelter for overwintering butterflies, and available foraging when the ground around is frozen.

The Royal Horticultural Society advises that ivy on the trunk does not strangle a healthy tree; if it manages to smother the crown it is often because the tree is already in a weakened state. There are some trees however, notably ash and others with a naturally sparse crown (which allow a lot of light to enter), which are more vulnerable and it is preferable to control ivy on these where possible.

Contrary to popular belief ivy is not a parasite: its suckers are merely suckers; they allow the ivy to support itself using the underlying structure, while the ivy's own root system provides all of its nutrients.

So the next time you see an ivy-covered cottage or wall, listen for the buzzing of bees. And when your immediate reaction is that the tree you're looking at is being strangled, stop to consider the possibility that actually it has a protective coat that allows a myriad of small creatures to survive.

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