How to Prune Hydrangeas
The trick to pruning hydrangeas is to know how to prune to shape and at the right time. One trick is to prune in spring rather than winter, this way it is easy to identify where the buds are and which canes are the best to keep.
Different Hydrangea varieties require different pruning techniques
Some Hydrangeas flower on old growth, others on new growth. This is where pruning techniques will differ.
- Annabelles, which are a common variety of Hydrangea arborescens flower on new wood and can be cut right back. These are a white flowering type that form large flowers to 25cm (10″) across. As they flower on new growth they can be pruned back hard every year. Best time to to prune is in winter.
- The macrophylla types.
These are plants that flower on last years wood (old growth), they form the flower buds the summer before, so if you hard prune they will have very few flowers.
- Mop Heads types are Hydrangea macrophylla also known as Endless summer or Big leaf. Generally they flower on both last years and this years wood, and they are bred this way.
- Lacecape types are Hydrangea macrophylla normalis and we think they are one of the most attractive types. They are pruned the same way as Mop Heads
- Oak Leaf types or Hydrangea quercifolia are characterized by the large oak leaf shaped foliage, flowers come as doubles and singles. They are woody and require little pruning at all, these are a hydrangea that prefer warm to hot summers, prune lightly after f lowering
- Paniculata hydrangeas often called PeeGee ( from the common form H.paniculata grandiflora or PG). These are a woody late flowering shrub that flower on new wood, these are the the ones with the ‘cone shaped’ flowers. You can deadhead them at any time, or prune them back from winter to spring. They are one of the easiest to prune and can be trained to form a single trunk, a bit like a standard. Prune huts about any time except when they have started to form the new flower buds.
Steps to pruning those that flower on old growth
- Identify dead wood or canes and use some loppers to cut these right back to good wood, or the ground.
- If you have an old plant that need a little rejuvenation, remove up to 1/3 of the old canes back to the ground.
- You should have a bush that is well formed and reasonably open, this promotes good air flow, if not remove other old canes to shape.
- Cut back all growth to the second set of buds from the top. Then remove any weak growth.
- Have a break and evaluate the shape of the plant, you could stop here, however if the plant is getting to tall you may need to look for buds lower down to prune to.
Steps to pruning those that flower on new growth
Some gardeners simply cut them back to the ground each year, however we suggest
- Removing old dead wood.
- Pruning away some of the smaller growth at ground level and leaving the strong older stems that are best formed.
- Open up the centre of the plant a little by removing ‘crossover’ growth.