How high do temps need to go to 'unthaw' my Nikko?
I'm in zone 5 MI, and have a Nikko and another semi-hardy to zone 5 hydrangea planted on a south facing exposure.
Last winter was cold and long, and all the flower buds survived the winter, I was so glad as I"ve heard there is mixed success in zone 5 and that most non-flowering Nikkos loose their blooms in late spring through the temps bouncing up and down a lot.
Every day, I"ve been shoveling more snow on top of the hydrangeas to keep them cold as the temps go into the low 40s.
At what point should I worry they are going to become "un-dormant?" Anything I can do to protect the blossoms?