Asked November 10, 2017, 9:14 AM EST
Harford County Maryland
The timing depends on what type of variety you have. Some (most) bloom on old wood, that is, wood that grew during the previous growing season. Pruning at the wrong time can sacrifice your flowers for the year. Another reason for lack of flowers is if the plant began to break dormancy (sometime if in full sun in a protected spot) and then the buds got zapped by a late winter frost. I had this problem for years with one of my hydrangea (Nikko blue). The leaves and shape were lovely, but never any flowers. Once I moved it to a better, north facing, more shaded location, it bloomed well.
Pruning to control height or to remove old flower heads depends on the type of hydrangea that you have and whether the hydrangea flowers on the previous or the current year’s growth.
Hydrangeas that flower on previous year’s growth:
Hydrangea macrophylla, Bigleaf hydrangea, Mophead (Pink & Blue types), Lacecaps
The bigleaf hydrangeas are the most common types in the landscape and flower on previous year’s growth. They can be susceptible to cold damage. Stems that have been damaged by cold should be pruned as soon as it is determined they are dead in the spring. Watch for new growth at the base of the plant. If the plant has basal shoots that are about 6 inches in length, but the upper parts are bare, then the bare stems need to be removed. Otherwise, prune shortly after flowering is complete.
Some of the newer cultivars like “Endless Summer” bloom on both old and new wood, so if winter damaged, you may have summer blooms. To control height prune after the first flush of flowers.
Hydrangea quercifolia, Oakleaf hydrangea – Flowers on previous year’s growth. Typically does not require pruning but if needed, in spring only remove dead wood. Otherwise prune after flowering.
Hydrangeas that flower on the current year’s growth:
Hydrangea arborescens, Smooth hydrangea, “Annabelle”, Grandiflora
Prune anytime from late summer until early spring. If pruning in the early spring, try to prune before leaves appear.
Hydrangea paniculata, Panicle hydrangea, PeeGee hydrangea, “Limelight”
Prune anytime from late summer until early spring. If pruning in the early spring, try to prune before leaves appear. Thin or cut back to previous season’s growth. Can become overgrown if not pruned.