Most of the other hydrangeas should be pruned in summer, once they have finished blooming.
Most of these bloom on what's called"old wood" - growth from the year before. If you prune them in early spring, you risk cuting off the dormant flower buds. By pruning right after the blooms have faded, you allow the plant time to set buds for the next year. Jan 06, Some people say that you can prune these hydrangeas as late as mid-August without affecting next year’s bloom, but it’s best to prune no later than the end of July just to be on the safe side.
In contrast, hydrangeas that bloom on new wood can be pruned any time except summer (panicled and PeeGee hydrangeas) or spring (‘Annabelle’ hydrangeas). May 10, Prune the hydrangea to reduce its size. If your hydrangea has grown quite large, you can prune it in June or July (just after the blooming season) to contain it a bit. Trim back the branches by 1/3 to the nearest joint%. Prune these hydrangeas only in the summer before August (to be safe).
Some experts believe these hydrangeas may be pruned even into August, but this might be risky. The hydrangeas may already have set their bloom buds for the next year. Bigleaf hydrangeas (Hydrangea macrophylla cvs., USDA Hardiness Zones 6–9) Bigleaf hydrangeas (H. serrata cvs., Z 6–9) Oakleaf hydrangeas (H. quercifolia cvs., Z 5–9) Prune after the flowers start to fade in late summer.
To determine if your hydrangea blooms on old wood, think about when it flowers. Jul 29, Hydrangea care involves planting them in partial shade, using mulch, frequent watering, occasional pruning, and optional fertilizing. Caring for hydrangeas is easier than most plants. Bigleaf hydrangeas practically care for themselves and aren’t prone to diseases.
In certain hardiness zones, they can survive winter without extra care.