My five year old clematis armandii has developed brown splotching on the the leaves of the oldest vines. In 2006 another armandii, in a large planter box, died after a very cold snap (minus 10). In the recent cold snap the temp only went to about minus 2. The armandii that froze lost all it's leaves and took two years to come back from the root. Is there anything I can do to save my gorgeous armandi that is at least 20 feet along the fence?