Answer: The most common reasons for hydrangeas not blooming are winter damage or spring frost damage, lack of light, and incorrect pruning.
Your zip code places you in zone 6B or the warmer part of zone 6. Hopefully the variety you planted is considered reliably winter hardy in zone 6 -- quite a few of the Hydrangea macrophylla varieties are only reliable to zone 7. In any case, a sheltered location with protection from winter winds is advisable. In spring, if the buds have begun to swell and a frost threatens, cover the plant to protect the new growth. If there is excessive winter damage or if frost damages the buds, you will lose blooming wood.
Hydrangeas bloom best with either morning sun or bright dappled light all day. In too much shade they will not form flower buds.
Incorrect pruning can limit flowering. These plants bloom on old wood, meaning branches that grew the year before. If you prune those off in fall or spring, you will remove the flowering wood. New plants would not need much pruning at all, witht he exception of removing any winter damage.
Finally, hydrangeas do best in a rich, organic soil. They also need evenly moist but well drained soil to grow their best, this means damp like a wrung out sponge, not saturated/sopping wet and not dried out. Using an organic mulch several inches thick year round will help keep the soil evenly moist and will also feed the soil slowly over time as it breaks down.
New plants can take a year or two to settle in and become rooted and established before they begin blooming their best. I hope they do better for you next summer.
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