Hydrangeas are considered 'caning' shrubs and they do produce new stem growth from the root crown. That's one of the supposed big advantages of selections like Endless Summer - even if they die back to the ground with winter cold, they will resprout from the base. It is also the concept behind rejuvenating old or very overgrown hydrangeas - removing upto 1/3 of the oldest canes each year at the base encourages the development of fresh, vigorous basal shoots. Older growth can indeed be 'spent' or fail to bud, whether due to old age or to cold damage - this is called dead wood. If there are no signs of budding (what you see now are only leaf buds) along these stems and the wood looks gray and dull, these can and should be removed back as far as you can. You can always check to see if the stem is still viable by scraping the bark. If it shows signs of moist, green tissue under the bark, it is still alive. If it looks dry and woody, it is dead and should be pruned out. When in doubt, the pruning of bigleaf hydrangeas can always be limited to the three D's - damaged, dead or diseased wood.

Photo 1: Yes, newhomeowner2011a, you can remove the blooms from last year. Photo 2: As for which hydrangea this one is, I think the blooms are too far away to tell. Limelight is known to produce greenish blooms that eventually turn white but a few others will do similarly for shorter periods of time. The size of the blooms could be that they are just recently opening now; not sure. Can you post another picture that more clearly shows the blooms (a close up? as best as you can with your camera?). Maybe someone will be able to tell from that picture. In your zone, many people have arborescens and paniculatas. A few oakleafs will do well closer to Zone 4b-ish. And some people have been able to grow macrophyllas that rebloom (their stems normally dry out during winter in very cold regions but new stems grow from the ground and develop blooms from these). By the way, enjoy the hammock!!!!!!!!!! I have one like yours too but the wood pieces broke last Fall and now need to replace them. Grrrr. Luis

Thank you all for your advice. I looked around on the internet and then went to a fine nursery which had Bella Anna, which I tbought to be beautiful and more than I had hoped for. The Bella Annas were in large containers and were a bit expensive but an employee pulled me aside and whispered to me that the nursery was having an unadvertised half price sale on a number of plants and all hydrangeas were included. I wish I had the space for several more but am grateful that I can put this one in! I will be there tomorrow as they unlock the doors and open the gates. I dont suppose that there is a reblooming blue flowering hydrangea similar in characteristics to Bella Anna - or is that just too darn greedy of me to wish for? ;) When I have extra time Im going to read that thread Hay started - I am familiar with him through another forum and am aware that there are very few that knows as much as he does about hydrangeas. What a gorgeous garden he must have, not just due to his hydrangeas but all the other planting beds he must have. Thank you all for your help and I am certainly going to explore Glowing Embers. If I must, other plants could be sacrificed to the gardening gods in order to make room for a new addition! The drawback would be the single bloom rather than reblooming abilities. I dont have a lot of room so all my roses and hydrangeas must be work horses. The only thing that can escape a rebloom and remain are my peonies. I only wish some genius could introduce a fluffy, frilly peony that would constantly rebloom AND would produce more the more you cut for the vase- what perfection that would be? Sadly, that will probably not happen in my lifetime. But, I can dream......;)

Something's off :-)) There cannot be two cultivars of bigleaf hydrangeas with same name. Not even if one is a trade or marketing name rather than a registered cultivar name. They just don't do that :-) It is against the rules of nomenclature. The "real" 'Shamrock' is a double flowered lacecap named for the garden in France that is home to the French National Hydrangea Collection. Possibly Everlasting® Green Cloud, although I wouldn't put money on it :-)