I have two hydrangeas, which are planted next to each other against a wall. They were planted about 3 years ago. I think they are the type which should be pruned in late summer or early fall, but I am not sure. Let's call the plant, which is blooming well, plant #1 and the one which only has one blossom this year, plant #2. Plant #1's blossoms start as green and turn a deep purple. Plant #2's blossoms (I think) started out as white and then turned blue. Late in the fall for 2 years, I cut both plants back, only leaving about 6 inch stems. I now think this is incorrect. Plant #1 still bloomed well each year. Are these plants different types? Should plant #2 be trimmed as soon as the blossoms begin to fade, but no later than early August (I live in the Philadelphia, Pa area)? If so, wouldn't I be deadheading flowers? Can you help me on how to prune these plants?
Certified GKH Gardening Expert
This article should help with pruning: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm
As for the blooming and color changes, these articles should help: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm