All my hydrangeas did the same thing. I have counted maybe 5 blooms total this year.

Like your hydrangeas, last years blooms were spectacular.

I assume the harsh winter is responsible.

What is bothering me most is that my Endless Summers are not trying to bloom on new wood as advertised. I expected them to bloom even if my heirloom mop heads that bloom on old wood only did not.

The blame goes to the horrible winter we had last year. Same thing with our mopheads; just a few blooms that the cold didn't kill off. Some hydrangeas bloom on the previous year's wood and when a bad winter comes along, it kills off the woody stems, hence no blooms or very little.

Almost all of mine failed to bloom. I know it's the winter, but they bloom in zone 5. Also most of mine are Endless Summer that bloom on new wood. Very frustrating.

The mopheads failed to bloom because they bloom on old wood; my paniculatas and serratas did fine; these bloom on new wood. Next year everything should be back to normal. Some even bloom on old and new wood! Some of mine didn't bloom because they are grown from cuttings and need time (about 3 years) before blooming. I did miss seeing my mopheads.

My Endless Summers are finally covered with tiny immature buds.
I hope the buds will bloom before the first hard freeze.

Yes, the Endless Summers do have tiny buds now...way too late. I wonder what the company would say about this. I sell them at Lowes and will be getting questions I'm sure. New wood should always produce blossoms in my book.

Now some of mind also have BLACK SPOT.

Glad I stumbled upon this. I have three David Ramsey hydrangeas which are supposed to be genetically identical to Endless Summer. They have grown (too well) and bloomed like crazy since the first year I planted them but they did nothing this year. I just went out and do see some little buds now.

They got bigger than described and I was thinking about moving them this fall but didn't want to go to the effort if something was wrong with them.