Great info, Thanks! My Hydrangea Macrophylla Mariesii Variegata has yet to produce a flower (Madison Wisc zone 4-5?). This is year 3 for both of my plants. They die back to the ground every winter. The foliage is beautiful. The plants are about 2 1/2 feet tall and wide now but no signs of any flowers and it is the first week of August. What should I do?
I made the mistake of buying this variety from my local garden shop (I am in zone 5). I later learned that It is a variety that blooms on old wood, so the dying back every year keeps it from ever blooming or getting very big. So, technically, yes it is "hardy" here but not in the way I assumed!
I've kept mine for over 5 years just for the variegated foliage. This last winter, which was milder than our norm and also had prolonged snow cover (also not normal here) must not have killed the stems completely to ground level, because I did get one blossom from a branch that arose from the base of a dead stem -- the first ever.
Maybe if you tried extraordinary winter protection. I am going to, now that I see there might be hope!