I have a few stems that are waiting until May. Since you are further north, you may want to wait 1-2 more weeks. It is a common problem with new hydrangeas but older ones should be leafing out more or less on time, plus or minus a few weeks. I doubt mine will leaf out after all the wild temperature fluctuations we had! Yours may also be dead but unfortunately, it is hard to tell for sure without access to a MRI Machine! Hee hee hee.

Or you could prune them in small increments until you see green or get to the bottom. The problem with this is youcould accidentally prune flower buds. If so, then plant will still bloom, albeit much later.

I believe you're mixing up two names for two different products - Forever & Ever and Endless Summer.

The general "cut-off" date for growth from old stems is Memorial Day. In most cases, new growth from old stems comes from actual buds, but *can* come from the nodes where the buds were, as long as the stems aren't dead. Endless Summer is very resilient in this manner, and not so much Forever & Ever (original).

Each winter, hydrangea macrophylla "pick and choose" which stems to let die off, in order to help protect the rest of the plant. Dead stems appear strawlike and almost hollow - almost white in color. Still-living stems are anywhere from gray to brown in color. The harsher the winter, the more dead stems you get. You can prune the dead ones out now, as long as you can tell these visual and sensory differences.

If no growth by late May from anywhere up top, it's time to consider trimming those stems down to where there is growth is seen. Bad years vary greatly here. For example, a bad winter followed by a dry summer will yield little or nothing from a mac.

This was a bad winter. Except for the hydrangea paniculata, everything else in my garden took big hits. Even the knockout roses got clobbered from 5' back to about 2'.