You can removed last years blooms from your hydrangea paniculata Phantom, it blooms on growth produced during the current year so you can cut it back quite hard without sacrificing flowers. With a young plant like yours, you probably have no reason to prune it severely - but you can certainly deadhead the spent blooms, trim out crossing branches and any that do not contribute to an attractive form .

With my own paniculatas, I wait until new green buds along the stems begin to swell, then will cut back to just above a strong bud...

Thank you morz8. Never had the tree form before and now I feel more comfortable about cutting off the dead flowers. I hope this tree will live for a long time. It is very beautiful. ********princesspeony*******