While walking through a woodland last week, I came across this (left). Wherever Ivy had grown up into one of the soaring mature trees, it had been cut away at the base, severing it from its roots. It must have taken quite an effort to do them all, and as a result each tree was wrapped in a rather unsightly dead shell of Ivy stems and leaves
It made me consider that perennial question - does Ivy harm a tree? It is especially pertinent to me as I have Ivy growing into two of my Sycamores.
What is known for certain is that Ivy does not actually suck goodness out of the tree - it is not a vampire. Those little 'roots' all up the stem are just there for clinging.
It is also clear that where the tree is nice and healthy, its own summer canopy is so dense that little light reaches the Ivy trying to clamber up the trunk, reducing its vigour.
But as a tree grows old or sick, and branches die, so Ivy is able to burst into the light and start to compete for light with the tree. It may indeed hasten its demise.
It is also possible that mature Ivy in a tree makes it more prone to windblow because of the added weight.
So it was then interesting to do a bit of Internet probing and find reference to an experiment at the turn of the 20th Century where the Ivy was cut on half the trees. Fifty two years later, the trees were measured. No difference was found to the final height, volume or girth of the trees, whether they carried Ivy or not.
Of course Ivy growing into trees is a natural process in our landscape. And in doing so it offers wonderful shelter, cover, nest sites, roost sites, and hunting grounds for wildlife, and ultimately blossom and berries.
Now that's not to say that people shouldn't remove Ivy from trees - it is their prerogative, and they may not like the way it makes the tree look. Or there may be safety risks with old trees. And isolated ornamental trees in gardens may suffer more than their woodland counterparts because the Ivy can receive more light than it would get in the shadows of a forest, speeding its growth.
But I think the important thing when faced with any decision is to understand the basic facts. And based on what I'm aware of, I know that I'm keeping the Ivy in my healthy Sycamores. Unless anyone wants to convince me otherwise!
I remember as a small boy taking every opportunity to squeeze myself right inside great thickets of ivy (probably causing huge habitat-disturbance, but I didn't know about that then!) specifically because that always seemed to be where the best bug-life was. These days I'm delighted when I hear late autumn ivy literally buzzing with activity as the bees and other invertebrates make full use of what might be described as 'the latest bar in town' (nectar bar, that is).
So, what ivy means to our rooted friends I'm not sure (though the study Adrian cites seems to suggest they don't mind), but to our six- and eight-legged friends I think it's a lifesaver - so I'm tempted to conclude that perhaps we should not let any single thing choke out everything else, but to allow a little room for a bit of everything (space permitting) ivy included - so, Jef, perhaps you inadvertently selected the best option: keeping your ivy 'in check' but allowing it to grow back...? All I would say is not to trim back the ivy flowers until the end of winter - don't want to be the one who shuts the 'late bar' early!