By Bernard
Cambridgeshire,
United Kingdom 
I have a weird problem with three clematis plants which are growing adjacent to each other. The first one is a montana 'Elizabeth' that was planted last year and was intended to climb an alder tree. Both this year and last it has commenced growing well, but at about this time the growing tops have slowly wilted and stopped growing. In two years it has only made progress up the tree or about 4ft. The second one, Mme Julie Correvon planted two years ago, did well last year, but this year it is producing tiny flowers with mis-shapen petals. The third one Comtesse de Bouchard grew normally and produced a good crop of normal flowers. This year it was pruned as group 3, but has romped off upwards and has now produced a crop of small flowers all at the top.
They were all fed in the spring and have been well watered since and the roots are shaded, so I am at loss to account for the weird behaviour. The only common denominator is the soil they are planted in and I am inclined to be a bit ruthless, dig them up and remove all the exiting soil and replace it with new, replanting with new plants, maybe only two this time but I thought before going off half cocked I would seek the opinions of GoY members who have proved so helpful in the past.
13 Jul, 2010
Answers
Really does sound like a water and food problem. Trees do tend to take all the water and food out of the soil before anything else can get at it. Some trees also exude anti-competition enzymes from the roots, not sure if Alder is one of them though.
13 Jul, 2010
Thanks for your responses, Bamboo and Owdboggy.
I water (when it hasn't rained) about once a week using a watering can with a rose and rainwater from a water butt. Each plant gets at least a gallon.
Bearing in mind Bamboo's comment about variations in the clematis performance, I wonder if I ought to be more patient and see what happens next year.
I wonder if you would be willing to recommend a watering and feeding routine that I should adopt from now on.
14 Jul, 2010
A gallon a week isn't enough if we're in a very dry spell, Bernard, particularly when there's a thirsty tree nearby. Make it 2 or 3 gallons the nearer the tree you get.
14 Jul, 2010
Any ideas about feeding?
14 Jul, 2010
Tomorite before flowering and Maxicrop after fiinishing. Mind I have to say I never feed our clematis, even the ones growing up trees. They grow and flower ok. They do take a while to settle down when planted under trees as they have to get their roots established in competition with the tree.
14 Jul, 2010
Thanks for your help.
15 Jul, 2010
The problem with the montana may well be related to water supply - you say it grows well initially, and then slows right down and stops altogether. As you want it in the tree, I assume it's planted fairly close to the roots of the tree, and that's a dry place to be from mid summer onwards (especially this year), so it just may be that they're not getting enough water at the roots. How you water is important, and that you haven't described.
As for the other two, apart from the above possibly applying, I don't know what to say - I have 2 clematis outside in different pots, both of which flourished and flowered prolifically last year - this year, one of them has been really miserable, producing a similar amount of foliage, but only about 3 tiny, weedy looking flowers.
13 Jul, 2010