Ask the head gardener: How and when should I prune my hydrangeas?

Telegraph

21-03-2025

Dear Tom,
Is now the right time to prune hydrangeas – and what's the best way to to do it?
– Sarah
Dear Sarah,
Towards the end of March, sap begins to rise, causing dormant buds to burst into leaf in many garden shrubs. This time of year is perfect for pruning hydrangeas, as we can easily see the parts of the plant that are alive and those that have succumbed to the winter chill, often resulting in a brittle shoot with no pliability.
Hydrangeas are wonderful shrubs to have in the garden and they flower spectacularly if you give them a little attention in spring. The majority of hydrangea species are deciduous, so they lose their leaves during the winter and foliage starts to emerge again when it warms up. This means they're vulnerable to late frosts if we prune too early, though.
The two most popular species in British gardens are Hydrangea macrophylla (mophead hydrangea) and Hydrangea paniculata (panicle hydrangea). When it comes to pruning, go steady: a very heavy hand will discourage flowers and promote lots of leaves instead, especially with the mophead types.
As with many popular garden plants, there are good varieties out there that will flower prolifically with strong growth, but there are plenty that won't. If you have an underperforming hydrangea but you're doing all the right things in terms of growing conditions and pruning, you may have a dud and you should consider replacing it (see my suggestions below).
With established mophead hydrangeas, wait until the buds have broken, then trim the ends of the stems back to the first or second pair of strong buds from the tip. You want to remove dead flowers and any frosted tips from the stems. Also remove spindly stems and a couple of older stems – you want to achieve an open, goblet-style shape, which will promote fresh growth from the base for future years.
With paniculate hydrangeas, pruning is not essential, but a light trim will promote larger flowers and presents you with an opportunity to remove deadwood. Hydrangea paniculata flowers will appear on growth made this spring and throughout summer, so, in early April, prune back to a strong framework, aiming to cut last year's growth back to 5–10cm from its origin. Remove any dead shoots that have no live buds, and any weak, inward-facing stems too. Again, an open shape is the objective here.
Young hydrangeas should be pruned minimally for the first few years to create a framework and strong root system. Neglected hydrangeas can be hard-pruned at this time of year to rejuvenate them, but flowering will be slightly compromised for a short time as a result. Climbing hydrangeas, including evergreen types, should be lightly pruned, to maintain a tight framework against the wall or fence that they're growing on, removing any deadwood from winter damage.