I'm in southern/central New Hampshire, in zone 5A, on the edge of 4B. I'm wondering how many people have had luck overwintering Endless Summer hydrangeas the first year that they're in the ground.
Last year, I bought one such plant. Of course it was gorgeous and blue at the garden center, but began to turn a bit pink/purple/grey once in the ground. Much to my delight, though, it bloomed again VERY late in the season, and was a rich blue. I guess my soil is acidic. I love that it will bloom twice in a season, and that it adds such a nice color at a time when most other flowers have died off. The blooms also last about 3 weeks, which is wonderful.
After reading some tragic tales about the fragility of these plants in their first year, I've been worried about this making it through the winter. I followed online instructions for overwintering in a cold climate... did not fertilize after X date (July 15, I think) and covered the plant with dried leaves before the first frost. Supposedly this is not necessary in areas that receive reliable snow cover, as we almost always do, but it's a good thing I did this - as it turned out, we received almost no snow until January, despite frigid temps. Now, of course, we've gotten over 3 feet just this month. In any case, we put 4 stakes in the ground, several inches away from the plant, wrapped the stakes with burlap to form a "container" of sorts, and then filled it all in with the dried leaves. The plant was never exposed directly to freezing temperatures.
Now, the plant is covered with several feet of snow, on top of the leaves.
I figure I've done everything that I can... but with our crazy cold temps right now (weeks of below-average temps, and that recent arctic blast where it got down to -20F overnight, not counting the windchill) I'm worried. Does anyone have stories of success in this kind of climate?