I had an email from a reader last week, asking if there was anything he could do with Clematis montana ‘Rubens’, which some years ago he had been recommended to plant to grow up an old, ugly apple tree.
Well, it had done that all right, apparently, to the extent it had almost smothered the tree and was marching off into next door’s garden.
The apple tree was, amazingly, still alive, as there were leafy twiglets sticking out through the clematis, but he felt it needed drastic attention.
I agree. At the least, it will soon kill the tree. At worst, the tree, plus all the weighty clematis, would blow over once the roots had started to rot.
In theory, it is possible to cut (or even saw) a really old montana almost to the ground, and it should start to sprout again from the stump. However, in practice, there is a fungus that can infect the sappy cut, causing the clematis to die back to the roots and kill the plant.
It has happened to one of mine in the past. However, as this monster needs some serious treatment, I would cut it hard back and keep my fingers crossed.
I am not a great advocate of growing any climbers up and into mature trees, as once they have reached the area you want to cover, it is difficult to control them and keep them this way.
They are much better grown on purpose-made supports of a height that you can get at them once necessary.
Even if you clip them back regularly (as I do with the Clematis montana trained on our kitchen wall), they will flower profusely, but can be prevented from getting out of hand.
In my opinion, about the only thing you can grow on a tree successfully is a strong-growing climbing or rambler rose, like ‘American Pillar’, but even this must be pruned annually in the same way as climbing roses grown in other ways. Most trees, even the most misshapen ones, are attractive enough at all times of the year to leave them without additional coverage.