Annabelles are pretty hard to kill, but no matter what they will look terrible this year if you transplant now. Early Spring or Fall is the best time to transplant. If you dont mind deep watering them basically daily and dont care if they bloom this year. You could attempt it and probably be successful. Actually I would pinch any buds/flowers on them to lower their stress and wouldnt feel bad shaving them back some also. The flowers more than likely wont come true anyways after transplant. We all this time of year want to rearrange things in the garden because it is full by this time of the year. We all can finally see what we are working with and want to make our changes to enjoy the rest of the growing season. But if you choose to do it now, I promise it will be a struggle. Like Springwood said next year though they will be fine. Its just all about how much trouble you want to put yourself thru this year. If you can wait till Fall you will save yourself a lot of hassle watering and can enjoy their flowers this year also.

It may be ok but I would choose a time when the plant is dormant instead. As soon as you see the leaves dried out plus 1-2 weeks, I would do it. Or in Spring before it leafs out. Since the soil freezes where you live, I would not even try in the middle of winter.

Rb, you don't tell us because you don't want us to know or because you don't know? Just kidding (gggg). Re: dieback. It's my understanding that PG trained as a standard and left to its own for years (typical example would be old PGs growing at cemetaries) could become very unkemp looking by the reason I call 'visual dieback'. I have an unsubstantiated theory about this and would be glad to have everybody's opinion about it. As branches become thicker and thicker bark on them become thicker as well, leaf buds can't penetrate it and new growth occures only at the tips of the old long branches. Some adventurous buds that still will be able to grow thru the old bark spend most of their energy to do so and are not productive. Since new growth is not produced anymore neither from the base of the tree nor from the most of the lenghts of the old branches you'll see new growth and flowers only on outside part of the plant. That is creating how I call it a 'visual dieback' effect. In a PGs trained as a trees this effect could ruin the whole appearance while in a shrub form it doesn't play such role. Hope you remember this pictures I posted here a few times Obviously nobody pruned this, planted in 1978, shrub for at least last 20 years. I got a chance to see it very close. Upon close inspection the main trunk become a 6 or 7 trunks growing together sometimes splitting, but sometimes growing one into each other. Nevertheless, of all 15-16' width of it, only outer 4 to 5' has viable buds in a spring, but that is enough to cover all ugly insides and create the most stately and gorgeous PG I ever saw.

Just pick a really nice day, and use a large pop-up bag to hold the spent flowers. Don't try to do them all at once, just enjoy the opportunity to be in the garden for an hour or two, and think about how lovely these will look in late summer. Dead-heading the hydrangeas is just one of those rituals that marks the start of the season. It's not a horrible task, if you love gardening, and it can be done when there are almost no other jobs that need to be done - except cutting back the ornamental grasses, transplanting shrubs and small trees, catching up with the winter weeds, dividing the most aggressive perennials, and turning the compost piles. LOL - this is in fact a very busy time in my garden!