I have 5 pinky winky shrubs that are finally at the very end of July just beginning to show some flower growth. I have a pinky winky tree that has been laden with blooms for many weeks if not a month. They have both had the same fertilizing. This is the second full summer in the garden. The growth was the same last year and I wonder if they need more time to develop or if there is a problem.
Hydrangea paniculata ‘Pinky Winky’ is a great plant and that is why you bought it in two forms I would suggest. Plants take time to adjust from their nursery conditions and that time could easily be a couple of years.Location in our yards also affects bloom time.
Both plants do seem to have flowers this year on different schedules. One is a tree form and they other is shrub form. Do they both get the same light? Are they both in moist but well drained soil? Did you prune both in the early Spring since these flower on new growth? Do you apply a mulch or well decayed manure in early Spring?
Most references refer to Hydrangea as a late summer to early fall blooming plant. In the Toronto area this year the hydrangea seem to be wonderful and blooming early. Sometimes nature likes to keep us guessing but your plants are on the right track.