Answer: You could transplant it in early spring, however the most common reasons for lack of bloom are excess winter cold damage and pruning at the wrong time. These plants bloom on old stems that grew the year before, so if the plant is killed back during the winter or if you prune it in fall, winter or spring, you will have fewer (or no) blooms. Also, late spring frosts sometimes damage the new growth and prevent blooming as a result.
Hydrangeas do best in sun all morning or in bright dappled light all day. In cold winter climates such as yours, they also need a sheltered location with protection from winter winds. The soil should be organic and humusy, evenly moist yet well drained -- like a wrung out sponge. Using an organic mulch year round is recommended. I hope this helps you trouble shoot.
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