Ivy: an insidious intruder?

The debate surrounding this unassuming shrub seems a particularly divided subject amongst the general public, gardeners and conservation bodies alike. Does ivy kill trees? Should it be left or removed? Is it an invasive species in need of control?

I was prompted to write a blog on the good old Ivy debate after coming across the slashed exhibits of many an ivy vigilante in the last week: from gardens to woodlands, I’ve noticed a surprising number of trees where ivy stems at their bases have had large chunks removed or simply been clean cut. This frustrates me no end, as I am a firm advocate of the beleaguered plant, and I shall explain why.

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a chopped ivy stem

Let’s set a few details down straight away: Ivy does not kill trees, and it is not a parasitic plant. Trees that succumb to ivy infestation are usually weak and under stress, and so are on their way out anyway. Healthy trees have a sufficient crown that inhibits the required photosynthesis thats allow ivy’s vigorous growth. And so if you see a tree utterly laden with the green stuff, it’s very likely it not be in a happy state of affairs, irrespective of the ivy.

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This Oak would have lost health due to external factors, allowing the ivy to take over the tree in a pretty fashionable style!

Furthermore, even where ivy does compete for light in unhealthy trees it supersedes, it does not directly tap in to a tree’s lifeblood of resources as do parasites like Misteltoe; the stringy roots you see sprouting from ivy are merely adaptations to provide support and facilitate its climbing nature. Ivy’s ‘real’ roots are anchored in the ground at the base of a tree.

Ivy, or Hedera helix, is an integral part of Britain’s woodland ecosystems. It is the country’s only native evergreen climbing shrub. Yep, that’s another thing: it is native – somehow our trees and woodlands have been coping just fine for centuries without our heroic efforts to control this tree-killing invader. The plant is as cemented amongst Britain’s flora and fauna as the Robin red-breast, or the humble Sessile Oak. I think the fact that the UK currently is just 13% forested is somehow down to the actions of other factors that I shan’t detail here…

Anyway – in addition to not being the devilish killer it may seem, the wildlife value of this evergreen plant is enormous. The tangle of branches entwining trees and the dense mass of bushy leafage provides perfect sheltered spots in which birds can construct their nests, and the plentitude of nooks and crannies are important day-roost sites for many species of bats. Come autumn, Ivy bursts into a mass of sweet-scented flowers, which acts as a veritable mecca for insects. Flowering as late as November, it is a very important source of nectar and pollen for bumblebees, butterflies, hoverflies, wasps and countless other insect species. There is even a recent colonist named after it’s dependence on this late resource: the Ivy Mining Bee, which is active late in the autumn and subsists almost exclusively on the rich provision from Ivy.

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The lovely Ivy Mining is a recent colonist to southern Britain, and ivy flowers constitute an import part of the specie’s nectar and pollen source (although they will also feed on heather!)

Over winter, the same tangled mess that allowed nesting spots for birds provides invaluable cover for insects, small mammals and birds escaping inclement conditions. By January, most mature Ivy plants will have set seed thanks to the pollinators it attracted in the autumn. These large, shiny-black fruits become an important food source for countless residents and winter visitors: woodpigeons, thrushes, blackcaps and starlings to name a few of the species that enjoy gorging themselves on the bounty. As a final plug for its habitat provision, there are beetles that bore into its stem, insects which feed on the tough leaf cuticles, and many spiders that construct their webs amongst the herbage to ensnare victims.

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The fruits are an important food source for many bird species come late winter

So returning to the burning issue: why do so many people seemingly despise the plant? I suppose it all boils down to context: whilst in woodlands and hedgerows it is perfectly fine for ivy to run rife in its natural state (in my opinion!), in parks and gardens it may be much less desirable. I don’t have a problem with gardeners controlling ivy where it may be considered a weed; those who like tidy gardens keeping it at bay through cutting (I’ll leave ‘tidy’ gardening to another post!). The big problem arises when people who are used to controlling ivy in these contexts develop a sort of vendetta against the plant, and extend their gardening ethic to the surrounding countryside. The bad reputation it acquires from it’s urban context results in a tainted picture of this species when people see it seemingly ‘smothering’ trees in woodlands. It must be controlled! I must save the tree from premature death!  Out come the saws and secateurs and the innocent stem is hacked in two: the dead skeleton of patterned roots clinging on like a spectre for weeks to come.

So, if you are an avid Ivy adversary, I hope I have convinced you to think twice next time you’re faced with the creeping stem of this unassuming plant. Please don’t succumb to the irresistible urge to severe the trunk in blatant ignorance of your effect: you’re not saving the tree. The only thing you’re cutting is the multitude of benefits this species provides.

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2 thoughts on “Ivy: an insidious intruder?

  1. John O'Brien

    I have a nature reserve and woodland In South Kilkenny and I had resisted cutting the ivy for years until recently. Then when saw two trees that I passed every day on my walks had been over come by ivy. One was a cherry tree that looked like an ivy tree and it never fruited and the only leaves that came on it was a tiny rosette type bunch on the top. I love the cherry fruit and use and collect them in season. So one day I go my saw and axe out because I was in fear of losing this tree because it was so top heavy and after 40 years I did not want to lose it. It has now turned into a magnificent tree with full cherry foliage even do its shape was changed a bit by the ivy. I did the same to a 30 year Hawthorn which I was in fear of losing because I use the berries and leave some for the birds. Glad I did this with fantastic results. Now my mission is to get the trees in my woodland back to the purpose they grow for and prevents me from losing more of my trees. I love my trees and my woodland. I am also in a position to say I have the Tallest Crab Apple tree in Ireland in my woodland. Ivy is not my best thank you Riverhollow Nature Reserve.

    Liked by 1 person

  2. Thanks for your comment John – interesting to hear about your observations from your reserve. Ivy can certainly have undesired effects in some situations. In america, for example, I am aware that Ivy is a big problem because of its introduction and resulting impact on native flora which aren’t adapted to its effects. Similarly in your situation perhaps, since Cherry and Crab Apple are not actually native species in the UK, maybe they succumb to Ivy for a similar reason? Just a thought

    Liked by 1 person

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