Hello, I have 2 oakleaf hydrangeas in font of my house (east facing). They are approximately 10 years old and very healthy. They grow upward and sideways fast so I usually trim them every year in late fall (I take off about 12 inches). They had been blooming beautifully with big white flowers changing the colors to dark burgundy in fall – UNTIL THIS YEAR (2024)!
Last fall (2023) my gardener took a liberty to trim them in my absence and they did not bloom this year. I am not sure if the reason for not blooming was improper trimming or something else.
Can you please advise about the proper way of pruning oakleaf hydrangeas, when to do it and what could be the reason for no blooms this year.
Thank you very much.
Olena
Hello, and thank you for contacting Toronto Master Gardeners with your question. Your plants look healthy, and the exposure, and past blooming history suggest that light and maturity are not the factors limiting flowering. It is likely that pruning was the source of the problem.
Hydrangea quercifolia, the Oakleaf Hydrangea, flowers on the previous year’s growth. This is also known as “flowering on old wood.” This means that any pruning needs to allow time for new growth to form and mature before that growth will flower. If you are going to prune Oakleaf Hydrangeas at all, pruning right after flowering (late summer) and leaving as much old wood with terminal flowering buds intact as possible, will ensure that plants continue to flower well. If you have the space, Oakleaf Hydrangeas will do well with as little pruning as possible. Pruning early in the season should be limited to dead or broken branches.
From the history that you have recounted we can guess that your gardener pruned the plants too late in the season and removed all of the mature buds that would have flowered this year. Your past pruning seems to have happened at the appropriate time and/or left enough old wood with mature buds on the plants to not interfere significantly with flowering. From the pictures, the space you have is somewhat limited. To keep the plants in bounds you may sometimes have to prune at a time of year that will sacrifice some mature branches. Being careful and intentional to leave as much mature growth intact rather than prune all the branches back will ensure that you still have flowers.
If you pruned the plants minimally or not at all this year, they should reward you with flowers next summer. They are beautiful plants, enjoy!