Answer: The bigleaf hydrangeas (Hydrangea macrophylla) bloom on old wood that grew the previous year. The most common reasons for lack of bloom are winter damage and/or incorrect pruning. These are often root hardy in your area (USDA zone 6A or the coldest part of zone 6) but may not bloom well due to winter damage to the stems. If your plant is killed back to the ground each winter, then it may not be able to bloom for you.
For the same reason, pruning in fall, winter or spring will remove flowering wood. In spring, be very patient and trim off only stems that you are certain are truly dead. Also protect the stems from late frosts that might damage buds that have already begun to swell along the stems. If you need to prune for shape or size, do that right after it blooms in mid summer.
Also, hydrangeas do need some sun to bloom well, either direct morning-only sun or bright dappled light all day. Excessive nitrogen fertilizer can also contribute to excessive foliage and fewer flowers. I hope this helps.
Q&A Library Searching Tips