I'm in zone 5b (Toronto). in 2013 I bought a Wisteria Blue Moon, it was blooming and on a small trellis. That winter it died down to the ground. During 2014 it bloomed with 2 small racemes of flowers and grew back about a foot. I protected it during winter and this year there were 6 racemes, but it also just grew another foot, not climbing at all. What could be the issue?