The paniculatas have been pruned because they will grow flowers on this year’s growth. If you prune severely to the first 2 buds, you’ll get fewer very large heads. If you prune to 5 buds you’ll get more but smaller heads. No pruning at all and you’ll get lots of very small heads. Where we have 2 plants of the same cultivar, we’ve experimented with pruning the front one to 5 buds and the back one hasn’t been pruned at all. The first is Hydrangea paniculata ‘Vanille Fraise’ pruned to 5 buds. The second image is the same plant but which hasn’t been pruned.