Hello, kaine23. Yes, ES is supposed to do well in cold zones such as yours. But you may notice some posts in here about blooming problems from people who have ES. Due to these bloom reliability issues, their website is now recommending some form of winter protection during the first few years, until the plant is well established. I am not sure what is up with that but I recommend that you follow the suggestions in their website (see the link below). Note too that the problem is reliable bloomage. Many people have ES with zero/zip/nada problems. Many of those people do not post here about that because there is no need to do that but an odd, i.e. high, number of people are posting questions about bloomage problems with ES. So, please consider this a f.y.i., not a 'do not buy' warning message.

Other mopheads that you could choose for Z6 are the Cityline Series, All Summer Beauty, Preziosa, Forever Series, etc. Other hydrangea varieties that would do well in Z6 are the arborescens, asperas, quercifolias (oakleafs) and serratas.

Here is a link that might be useful: ES Website

Hi kaine23,
I have had 2 ES for at least 4 or 5 years now. It is the most reliable plant that I own. I've also potted up so many plants for friends and neighbors that I can't count. Go ahead and get your ES. You won't be sorry you did.

owervinterin is problem for ES. Nikko Blue scored better than ES although they are located 2 feet apart from each other. i didn't do any winter protection in Brampton, Ontario, Canada., and I could be in Zone 5 and/or 6 if those zone #s mean anything. last summer ES did bloom very, very good, huge blooms.