I have several Endless Summer – Twist N Shout, and Blushing Bride plants who had numerous flowers for the first few years and now are producing only 1 or 2 flowers. I apply soil acidifier in the spring. I have been adding ‘flowering fertilizer’ this spring in the hopes that I would see more flower buds, but so far there are only 1 or 2 flower buds.
Thank you for contacting Toronto Master Gardeners.
We have had many questions regarding hydrangeas and lack of blooms. I’m sure it must be particularly frustrating when you anticipate a full season of beautiful flowers.
Endless Summer varieties, cultivars of Hydrangea macrophylla, produce buds, then flowers, on old and new wood. Winters the last two years have been severe, with significant temperature fluctuations. It is advisable to apply mulch in autumn close to but not touching the crown of the plant to protect the root system. If the plant is exposed to strong winds gathering the branches together and wrapping in burlap, or building a burlap enclosure around your plants will protect the buds that have formed on old wood from freezing.
Has the amount of light/shade changed where your plants are located?
The three numbers on fertilizer represent the value of the three macro-nutrients used by plants. These macro-nutrients are nitrogen (N), phosphorus (P) and potassium (K) or NPK for short. I assume that the “flowering” fertilizer you use has a P content higher than either of the others. Phosphorus is the nutrient that encourages development of roots and flowers. It is best applied in early spring.
These plants do not need pruning, except for removal of dead flowers, dead branches.
For more information on care of these beautiful shrubs, consult the links below:
https://extension.psu.edu/why-doesnt-my-hydrangea-bloom
Hopefully your plants will develop flowers on new growth.