Answer: Your zip code places you in a nominal zone 5B or the colder part of winter hardiness zone 5. Unfortunately, most hydrangeas are only reliable bloomers through zone 7 and sometimes into zone 6 although they may be root hardy in colder areas than that. So I suspect what has been happening is that your winter weather is so cold that the plant is suffering winter damage. This can kill back the stems and/or buds and cause the plant not to bloom. The other possibility is that the plant is being hit by frosts in the spring when the temperatures can oscillate back and forth, again with the same result. Yet another possibility is that you are pruning it back in the spring and removing the flowering wood. This plant blooms on old wood, so you would need to take steps to protect the stems and tender new spring growth -- and definitely avoid spring pruning. Some people do this by erecting a wire mesh cylinder or fencing around the plant and filling that with dry, non-packing material such as straw or oak leaves and then topping the cylinder with plastic to keep it dry. Put it up in very late fall and remove it in the early spring after the worst of winter, but keep insulating material handy to cover the plant on cold frosty spring nights that hit after it has begun to grow. This can be a lot of work but some people have gorgeous zone 5 hydrangeas this way. I hope this helps.
Q&A Library Searching Tips