I am not going to say exactly how long ago so as not to date me but I once killed a new Annabelle that was planted in the fall. I diagnosed the problem then as a lack of enough water. At the time, I turned off the drip irrigation because we were going to have cold weather for an extended amount of time. Unfortunately, it was a dry winter and I did not re-activate the drip system until some evergreens began to develop brown leaves. Annabelle had gone dormant so I could not detect lack of watering issues by visually inspecting it. The plant did not come back. Ever since, I keep an eye on soil moisture during winter too in my mild winters. Another possibility is root damage from pests like voles, etc. Also, make sure that you are planting them slightly above the soil line.

I don't know what to tell you :-) Zone 8 western WA should be about the easiest place on the planet to grow hydrangeas! All types thrive in our cool summers, mild winters and plentiful rainfall.

My only input is that the rabbit predation may have been overwhelming for a young, yet-to-be-established shrub. And voles are a distinct possibility. Also last winter's very abrupt and sharp, extended cold snap immediately after Christmas may have been too severe........but that seems unlikely for a plant with the hardiness of H. arborescens. It didn't get that cold!! Certainly not cold enough to damage or bother any of my hydrangeas - mostly macs - growing in containers left outside all year long. They are all budding up.

I'd try again.

What is its siting? Sun in the morning and afternoon shade is ideal for this type of hydrangea. It will need adequate water, especially for the first year, but any time there is an extended time period without significant rain, which is much of the summer in the PNW. I sincerely doubt it is a temperature issue since I can grow it without problems on the cold edge of zone 5.

Weather definitely had nothing to do with it; I see all kinds of H's everywhere in WA. From what I understand, Incrediballs especially prefers to be in full sun. The one that didn't come back was in full sun, and the other was in part sun, part shade, but bright enough to do well. I typically don't water much, leaving the watering to the rain (it's WA). Now that you mention it, I might not have watered enough. And yes, they were both planted about 1" above soil line. I have very very clay soil. It's hard for me to dig even the smallest hole to plant anything. I wonder if that affects Hydrangeas. I'll water more to see if that makes any difference before I let go.

Thank you all for all your inputs.

Try to get the soil moist all the way down to a depth between 4-8" after watering. I would give it some extra time but if you decide to remove it, see if you notice anything odd in the root system or soggy soil in the clay soil.

My guess is either animal damage or the roots sitting in a pool of water and rotting or not being able to grow into the heavy clay. In the future, you need to dig a deep hole that allows drainage.