Hi Stephanie.

Thank you for reaching out to the UVM Extension Service Hot Line.

Pruning hydrangeas is a subject that baffles many gardeners - novice and experienced alike. Before you grab your pruning tools, you need to identify which species you have in your garden.

There are several species of hydrangeas commonly grown in New England, and all of them have very different growth habits and pruning requirements. While some plants bloom on new growth, others primarily set flower buds on old wood.

Once you confirm that your plants are varieties that bloom on old wood; either Hydrangea macrophylla (big leaf hydrangea) and/or Hydrangea quercifolia (oakleaf hydrangea), should not be pruned in late winter.

Wait to prune your bigleaf hydrangeas until new growth appears in the spring. Flower buds are produced at the tips of stems on old wood of the previous year. If those buds are killed or damaged, the hydrangea’s flowering potential is reduced; although lower buds along the stem have the potential to develop flowers too. Make pruning cuts one quarter inch above the first set of live buds. (Hint: stems with live buds will be green on the inside, while dead stems will be brown. Entirely dead stems should be cut flush to the base).

Hydrangea arborescens (smooth hydrangea) and Hydrangea paniculata (panicled hydrangea) grow blooms on new wood —therefore allowing for a late winter pruning.

I hope this is helpful for you to go forward with your pruning project.

I’ve included some additional extension resources on hydrangeas below.

Happy Gardening, 

Selecting Hydrangeas for the Home Landscape 
Hydrangea Selection, Pruning, and Care 
Solving the Hydrangea Puzzle 
Hydrangeas in the Garden