We do have higher humidity, but it could be a combination of things. There are many conversations online of people talking about problems with these plants though. Some people complain of nemotodes. Others say their plant goes dormant in the summer. Some say their plants just don't return after winter. I have never seen a perennial this difficult to grow here. It grows much the way Delphiniums do. They won't grow here either. I bet they do well in similar zones.
