I'll tell you what I did and then decide if it is suitable for you. First, I'm in a warmer end of z6 and only on a rare ocassion all buds of 30+ macrophyllas I grow got killed. So, I didn't protect any of them and had no serious reason to grow ES since there are many much more interesting hydtangeas. However, I had one particular spot in a garden where macs don't want to bloom even after relatively warm winters. Problem with this spot is that it's in a full sun the whole winter and early spring and then become part-shaded as season progresses. What usually happens there is that hydrangeas buds start swelling very early and got zupped by March frosts. I planted three ES there last year and usual thing happened again even though we had an unusually warm winter. On April 1 I pruned all three of them to 6-8" off the ground leaving two pairs of live buds on a stem. By July they produced a lot of new growth from the old stems as well as from the base. First bloom occured on or about August 1, 4 months after pruning, on a new growth from the old stems and since then they are in a CONSTANT bloom because new growth from the base also produced flower buds, but 1-1.5 months later than the first set. This picture was taken last week. As you can see, right now I have a combo of aged (pink), semi-aged and new(blue) flowers on a same plant. Though plants are only 2'+ tall (no wonder with such severe spring pruning) I finally made hydrangeas bloom in that spot. How all this should be translated to z5? Unless you want to go a long way to protect current year top growth and have a mid-summer bloom, you may instead simply settle for the late-summer bloom on a new growth and do nothing, except mulching to protect the root zone.. Before ES was invented you had no luxury to chose the bloom time. Now you do.

I have not seen an endless summer with so many beautiful flowers for a long time! with our harsh winters for the last couple of years, my ES's only have a few blooms on each of them last year. This year (with milder) winter, there are a few more flowers. But one of them only has 3, one has none, 1 has ~ 13. These 3 are not winter protected and are in morning shade and 3 hrs afternoon sun. The one in the back yard (2-3 hr morning sun, all afternoon shade, close to house so more sheltered) has a lot more blooms (but much less than yours). So I think location is really important for us northern gardeners and 2-3 morning sun is more ideal. This one performs much better than the ones in 2-3 hr afternoon sun, every year since I had them 6 years ago. I will try to winter protect this winter.

Is it a heated garage? Did you water it while dormant? Sorry @luis_pr for the delay in replying. The garage is not heated (the coldest I observed inside the garage was -12 C/10 F while it was -22 C/-8 F outside) and the only water it got was from 'clumps' of snow that I would put on it every once and awhile through the winter. So here it was on May 17: And today, about 6 weeks later: I can tell you that it looks lots larger than it actually is, but clearly it is producing flowers (on strictly new wood).

Congrats! I know how tricky these can be for those in colder zones so enjoy your bounty :-)) And I have to say this looks like a banner year for hydrangeas in my area as well. Not only with flowering but the plants themselves are growing like they are on steroids! I may have to do some pruning later.