I have two hydrangea paniculatas in my front yard. They are about 12 years old. I prune them every year early in the spring to remove the dead flowers and in the past couple of years I have done so to try to decrease their size a bit. But they seem to have exploded with growth and are now taking up a big footprint and shading things underneath and behind. These were in full sun but the City planted a tree in front of them so they are now in part shade. Sandy soil. I have two questions – when is the best time to prune these to decrease their size? And is it possible to prune these into a tree shape (in other words, could I remove all the branches on the bottom and just keep the ones on top? would the bottom branches grow back?)
Thanks for your question. Hydrangea paniculatas are very beautiful.
To get you started, Toronto Master Gardeners has a Garden Guide that covers a wide range of questions about hydrangeas. For more information on hydrangeas please visit our TMG growing guide.
In general, hydrangeas need moist, well-drained soil and protection from strong winds and the hot afternoon sun. Light requirements vary by variety, but typically, hydrangeas need at least four hours of sunlight daily, ideally in the morning. These plants don’t like competing with tree roots for moisture and nutrients, so avoid planting them directly under trees.
The good news is you are pruning your hydrangea paniculatas at the right time of year. In terms of pruning to reduce the overall size, hydrangea paniculatas can take a very hard pruning. It can be pruned down to near ground level in the spring, if desired and you will get strong new growth from the bottom which will bloom for you in the same year.
In terms of pruning your shrubs into a tree form or “standard” the good news is that hydrangeas are a plant that lends itself to a standard form; the bad news is your shrubs maybe a bit too mature (12-years-old) to reshape from a multi-stem shrub into a single stemmed standard. Nothing is impossible, but typically standards are created with very young plants.
The Royal Horticultural Society provides this multi-year guide to creating a standard tree.
For more information on pruning hydrangeas see this helpful YouTube video from an ornamental horticulturist.
I hope this answers your questions and thanks again for contacting Toronto Master Gardeners.
October 14, 2022