Some reasons why your hydrangeas aren’t blooming
“I purchased some beautiful blue hydrangeas a few years ago, and they have not performed well since the first summer. The few flowers I do get are more of a pink color versus the blue color I purchased them for. What can I do to improve these plants?”
— Carol Quinn, Chicago
You most likely purchased a cultivar of a bigleaf hydrangea (Hydrangea macrophylla). Some of the older varieties, such as Nikko Blue, are at the northern edge of their hardiness zone in the Chicago region and flower on 1-year-old wood, which often dies back after winter.
A large number of flower buds will then be lost after a typical cold Chicago winter, resulting in diminished flowering at best. Late-spring frosts and deer browsing can also decrease the number of flowers.
If these hydrangeas die back to the ground or even partially back after a very cold winter, there will be no flowers in spring. The hydrangeas will resprout from the base and develop healthy green foliage, but no flowers.
It is likely that your hydrangeas are losing flower buds due to winter cold, late-spring frosts or deer eating the buds. Mulching the plants and wrapping them with burlap may help get them through the winter, but are long-shot maintenance techniques.
Pruning at the wrong time can also remove flowers. Do not prune them back hard in late winter or early spring (as is commonly done with Annabelle hydrangeas).
As the flower clusters of
your hydrangeas are fading in late summer, prune just below the flowers if you want to reduce the size of the plant. Then in spring, prune just above the first set of buds. Give the plants extra time in spring to leaf out before determining whether or not the stems are dead and need to be pruned back.
There are new varieties of bigleaf hydrangeas that flower on both old and new wood and should be more reliable in flowering. Some of the new cultivars are ‘Endless Summer,’ ‘Twistn-Shout’ and ‘Blushing Bride.’
Soil pH affects the flower color, producing more blue in acidic soils and pink in slightly acidic
to alkaline soils. Add elemental sulfur in spring and fall to lower the pH of your garden soil surrounding the hydrangeas and improve the chances for blue flowers.
I think your best bet is to explore replacing your current hydrangeas with a new, more reliable cultivar of bigleaf hydrangea or a different type of hydrangea that will be much more dependable for your garden.