The subject of ivy on trees seems to evoke a partisan response. There are those who insist it strangles trees and those who say it does no harm at all, in fact has tremendous ecological value. I have mentioned in several posts recently that ivy is indeed a great plant for wildlife: bugs, bees, birds, bats et al.

 I would think then that this ivy covered oak is an especially good combination in that regard. Oaks are top of the tree (pardon the pun) for nurturing wildlife. Then again I have some sympathy with the idea that a tree shouldn't be entirely subsumed. By the way, this oak was only a few inches tall when my parents bought the house!

 Opposite the oak is a walnut tree where the ivy has climbed to the very top and is spreading out along all the branches. I've made the decision to "ring" the ivy at about head height. Likewise there is a tall and ancient pear tree adjacent to the oak. It used to crop very heavily when I was a child and still flowers a little even now without producing much.

 I rather think the walnut tree wouldn't be adversely affected by ivy for a long time, if at all. So perhaps that's more of an aesthetic decision but my instinct is that the pear tree in its dotage would not be well served by a mass of ivy on the branches. I have also heard it said that voluminous ivy increases the wind profile of a tree and I think there might be something in that.

 There's plenty of ivy in the garden and I will leave it on the oak for a few years yet. If and when I do give it a chop the ivy will be climbing back up the walnut by then. Essentially I don't think there has to be an all or nothing approach though as I say the topic seems to divide opinion.

 NB I wait until ivy has flowered before I cut it back. Where trees are concerned "ringing" ivy seems to me to be preferable to ripping it out altogether i.e. cut the stems all around the trunk (very important not to damage the bark of course). Ivy remains green for months afterwards so any living things overwintering in it will have shelter. The leaves eventually brown and drop off and the stems wither.