This was planted in our heavy clay soil (which is gradually being improved with grit, farmyard manure and our own compost) in February 2004. It has been doing very well since, flowering well this year and now covering the roof of the shed. But it seems to be dying and there are no new young shoots. It is not entirely dead: when I scraped a tiny part of an area close to the base it was green not brown. I have started to but back all the dead part in the hope that it will revive but I would love to know what I have done wrong. How on earth could anyone kill a clematis montana rubens?