Mildew on Clematis

The Bird Lady

I have severe powdery mildew on 4 of my 8 Clematis, oddly all of them are potted.  The ones in the ground are fine.  Nothing to be done I suppose, apart from cutting them back to the base.

Fire

I've been taking it to be something to do with under watering, but I have fed and watered and nothing seems to be shifting it. My new plants look so miserable. I feel like a bad parent.

The Bird Lady

I'm glad it's not just me!  My plants are well cared for (or so I thought!) but still they suffer.

Guernsey Donkey2

I have what was a healthy clematis growing up a trellis against the wall, mixing in with a climbing rose.  Now I find the leaves of the clematis are dying (brown and easy to remove) and the flowering stems are a green/white colour, the flowers look reasonably o.k. but with a tinge of white on them. Is this caused by over watering, lack of feed or something else?

Richard Hodson

Powdery mildew sets in when the roots are too dry and the plant is stressed, you need to get more water under the roots. For plants in pots it is a good idea to stand them in a large saucer and water from underneath.

Fairygirl

Is the rose also stealing a lot of moisture from it, GD?
Against a wall is always trickier for keeping plants moist enough too. 

Guernsey Donkey2

Since posting my question I have taken a couple of pictures of the poor clematis and thank you @Richard Hodson and @Fairygirl for your suggestions.  The clematis isn't in a pot, it is growing in the bed and up a trellis attached to a house wall.  I must admit I thought I was watering it too much but if you both think the plant is being underwatered then I shall give it more or at least more often. All the other plants along this border are doing well, so this mildew really stands out, although you can see I have some black spot on the rose although I don't use any chemicals, I pick the affected rose leaves off from time to time.