Pieris Forest Flame - can it be pruned back

my sister had a huge one in her garden and she chopped it down couldnt believe it. anyways this year it has sprouted new leaves and ive told her to leave it alone. dont know when the correct time is to prune but someone will be alone shortly to let you know

Wait til it has flowered, then prune back. Don't take off more than a third tho', the shock of being pruned may be too much to start with. Then trim it lightly every year after flowering.