Yes, that is typically the approach. I assume though that you scratched the stems near the bottom of the stems? ... because some stems can leaf out from the middle or further down. If they have not leafed by mid-to-late May in the northernmost and coldest half of the country then "have at them"! Down here, I do the pruning around late April to early May (the exact time can vary depending on how "long" winter is}.

I have had only a handful of times when all growth came from the crown and one of those dried out looking stems managed to leaf out late.

You can use winter protection to try and prevent this in future years. Hopefully, ES and BB will be true to the advertising and develop new bloomage in the summer/Fall for you.

Luis

PS - I forgot to mention that even down here in warm 8A, this problem can happen. All of my mopheads went dormant late last December but, the temperatures remained mild enough. For hydrangeas that equates to something like us sleeping with someone that snores nearby! LOL! I knew I would be in trouble if temps went down low/hard enough because I hardly ever winter protect. Around January 5, temps crashed down good, eventually hitting 19 and now I have a lot of mopheads with all growth from the crown too. But, some that are in 'protected' locations have a few stems that made it and are in the broccoli stage. Again, I hope you get some bloomage, mtz96!

ES BB is the least winter hardy in the ES series. I would not recommend overwintering it outdoors in anywhere but subtropical areas (z7-10). ES Bloomstruck is the most winter hardy followed somewhat closely by Twist N Shout and then Original (which is about the same as Nikko Blue).

You can also flick the old buds lightly with your finger. If they flake or fall right off or turn to mush, they're dead. Very dark brown or black, they're most likely done. Buds that survived should have some green visible by now, otherwise they'll be colors ranging from dark to bright red to brightish brown and somewhat shiny and solid.

I have had these hydrangeas for several years. The buds on the stems are dried up (dead). I am assuming that I can go ahead & cut the stems to the ground since I have a lot of new growth coming from the ground. I am in east central Iowa...zone 5