I have had my canna lillies and elephant ears for 6 years and every year they have returned and grow as high as 9 feet tall. However this spring they did not return. When I pull at a old shoot (canna lily) it is as through its rotted. The elephant ears have not returned either. What could have caused this. I am terribly upset as I enjoyed seeing the tropical plants around our pond each year.
Our entire region has experienced, this year, one of the many alternating cool and warm periods. Since you are on the edge of where they can survive, This means that during this time where the sun and earth are a little further apart than usual, and the sun is a little cooler than usual, it is possible to lose plants that are right on the line of where they can survive. This is unfortunate, and somewhat unavoidable.