Hydrangeas, like all plants, follow a specific growth cycle that dictates when and how they should be pruned. These deciduous shrubs bloom on either old wood (previous year's growth) or new wood (current season's growth), depending on the species. For example, Hydrangea macrophylla (bigleaf hydrangea) blooms on old wood, while Hydrangea paniculata (panicle hydrangea) blooms on new wood. Pruning at the wrong time can remove flower buds, reducing blooms for the season.
The timing of pruning depends on the hydrangea species:
Old-Wood Bloomers (e.g., Hydrangea macrophylla, Hydrangea quercifolia): Prune immediately after flowering in late summer or early fall. These plants set flower buds in late summer for the next year, so pruning in spring or winter removes potential blooms.
New-Wood Bloomers (e.g., Hydrangea paniculata, Hydrangea arborescens): Prune in late winter or early spring before new growth begins. These species produce flowers on current-season growth, so pruning encourages vigorous new shoots and abundant blooms.
Proper pruning techniques ensure healthy growth and abundant blooms:
Step 1: Remove Dead or Damaged Wood: Start by cutting out any dead, diseased, or broken branches at their base. This prevents energy waste and reduces disease risk.
Step 2: Thin Out Overcrowded Stems: For dense shrubs, remove about one-third of the oldest stems to improve air circulation and light penetration. Cut these stems at ground level.
Step 3: Shape the Plant: Trim back leggy or unruly branches to maintain a balanced shape. For old-wood bloomers, avoid excessive cutting to preserve flower buds.
Step 4: Encourage New Growth (New-Wood Bloomers): Cut back stems to 12-24 inches above the ground to stimulate strong, flower-producing shoots.
Older or neglected hydrangeas may require rejuvenation pruning:
For New-Wood Bloomers: Cut the entire plant back to 6-12 inches in early spring. This drastic method encourages fresh, vigorous growth.
For Old-Wood Bloomers: Avoid severe pruning. Instead, remove a few oldest stems each year over 2-3 years to renew the plant gradually.
After pruning, support maximum growth with proper care:
Watering: Keep the soil consistently moist, especially after pruning, to help the plant recover.
Fertilizing: Apply a balanced, slow-release fertilizer in early spring to promote healthy growth.
Mulching: Add a 2-3 inch layer of organic mulch around the base to retain moisture and regulate soil temperature.
