Answer: The most common cause of failure to bloom is winter damage and/or pruning at the wrong time. Most hydrangeas bloom on wood that grew the previous year. So if the plant dies back during the winter, or if it is pruned in fall, winter, or spring, then it will not bloom the coming summer.
If you find that your plant is dying back to the ground each winter, you may want to provide it with extra winter protection and see if that helps. Also, do not prune in the spring except to remove truly dead branches. Hydrangeas can be late to leaf out, so do not prune prematurely.
Sometimes buds are damaged by spring frosts. If your plant has already started to grow and a frost threatens, cover the plant to protect it from the frost.
I hope this helps.
Q&A Library Searching Tips