Two years ago I mistakenly trimmed my hydrangeas in the spring (May 2015). They were established and had been blooming for 3 years. Unfortunately, they have not bloomed since I trimmed them. From everything I read I would not have expected them to bloom in 2015, but they should have in 2016.
My garden is on the garden tour this year and if there is something I can do to help them bloom this year I would very much like to try.
I look forward to receiving your suggestions.
Thank you for contacting the Toronto Master Gardeners with your inquiry.
We receive numerous questions from Toronto gardeners concerning their non-blooming hydrangeas.
The key to getting your hydrangea to bloom is in knowing what kind you are growing. Some hydrangeas grow flowers on new wood ( e.g. PeeGee, Annabelle) and some on old wood. From your description it sounds as if you have hydrangeas that bloom on old wood. These are the big leafed species (Hydrangea macrophilia), which happen to be the most popular.
Even if you have not pruned, these cultivars can die back in the winter, particularly if there’s been a colder than normal winter or a late frost. If the old wood dies, your hydrangea won’t bloom when it grows back the following year. This is because it’s growing new wood and the new wood doesn’t produce flowers on this particular variety. You will have to wait for the following year.
If you do not have flowers this year, and you haven’t pruned, it is very likely that the flowering buds which are formed on the old wood are freezing out. Try protecting your plants this winter by surrounding them with burlap and see if that makes any difference.
As mentioned, we receive numerous questions concerning Hydrangeas. The following link contains information that has been pulled together from other Toronto Master Gardener ASK posts, which I hope will help: Hydrangeas- Blooming, Growing Pruning