whats wrong with my hydrangea

[nakanj]

I have two Hydrangeas about 3 ft, tall. This winter they had aphids bad and I used insecticidal oil to kill them Now they won't bloom. They are both healthy looking with nice green leaves but no blooms. Did the oil hurt them someway that I can't see?

[hendi_alex]

Some hydrangeas bloom on new growth and others bloom on last season's growth. If the hydrangeas which bloom on last season's growth die back because of a particularly cold winter, then they will not bloom the next year. I have two of those hydrangeas and neither is blooming this year after this past winter's very cold temperatures. So depending upon your particular type of hydrangeas, winter kill of last season's growth could be the culprit.