It is finally cold enough that I consider most plants dormant, and I have a lot of pruning ahead of me. Above, you see an unpruned Hydrangea paniculata v. grandiflora (peegee hydrangea). Notice the four feet of stem growth from 2015, with the big, dried hydrangea blooms. This five year old shrub produced dozens of big, beautiful white blooms last summer.
My stewardship involves cutting back those long stems to keep the plant balanced, and removing weak, distorted stems. I also remove rooted stems from the mulch, and replant those bonus plants.
Timing is key when it comes to pruning peegee hydrangeas. The summer blooming peegee hydrangea blooms on new (or this year’s) wood, hence, winter or very early spring pruning back to a strong matrix. The French (or mophead, or Hortensia) hydrangeas bloom on last year’s wood, in general. Pruning them now will result in loss of next year’s blooms. When in doubt, do nothing. I see many people pruning in the fall as soon as leaves drop, and this isn’t a good idea on the peegees. But, lots of folks just can’t wait to clean up their gardens.