Answer: Unfortunately I am not clear which plant you are calling a hydrangea tree. I hope it is the PeeGee hydrangea or Hydrangea paniculata. This woody shrub is sometimes trained into a tree form. It should be fine in your winters without too much extra protection beyond mulch. In late fall after a few freezes, mulch over the root areas with an organic mulch in a layer about six inches deep. Keep it away from touching the bark. That's all they should need. In the spring, be very patient waiting for these to leaf out, they are slow. If there is winter damage that causes branch tips to die back, trim them off in the spring when you are sure they are dead. Dead wood will be brittle, off color gray or brown and will snap in your finger. Live wood will be supple, have green inside the bark, and the buds will be plump and firm. Late winter to early spring is also the time to prune these if you need to correct the shape. They bloom on new growth of the season, so do not prune them in the summer. Good luck with your hydrangeas!
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