Hey plantcollector, I live in NE Ks. I bought one three years ago, or was it 4? It is planted in sun/dappled sun in a.m., shade in the afternoon. No blooms, ever. The first winter, (this is really kind of comical, to me anyway) I used an old laundry basket, flipped upside down, drilled 1/2 holes in the bottom, then used a xacto knife and cut kind of a flapper of the bottom, so I could stuff leaves down inside. Then I used like tent stakes to hold the basket down. It didn't freeze to death, it still had old growth which promptly greened up the following spring. Well, didn't do the basket the next year, it has always come back, but no blooms. I know there is an elaborate educational post on winterizing hydrangeas over on the hydrangea forum. Might check it out, VERY good reading. Bet that "yard" sale was a blast!

Plant, there are numerous types of hydrangeas. You need to ID yours..is there a way you can contact the nursery you got it from and inquire?
Yep, there are hardy types, as low as z4..I've two types in my gardens..One is a bush, the other a tree. Leaves differ from each other on both plants..One has longer, soft leaves, the other has small, firm leaves.
I'd try contating the seller, either by phone or email.
BTW, does the tree have several plants or is this one tree? It sure sounds gorgeous..Anywa, if there's more than one plant, you can try setting one outdoors, the other in a pot and see what happens next spring. Toni

This is a little late, but I'll post anyway..... I have had this hydrangea in Zone 6 for about 6 years now. Not a single bloom. I have moved it several places and tried various ways of protection to no avail. This winter I potted a nice rooted cutting in a large container and I am going to try to overwinter it in an unheated garage and see how it works. Thankfully, it's a nice looking shrub without the flowers so I still have one in my garden....