How do you make hydrangeas bloom?

SOLUTIONS For growing Hydrangea macrophylla and Hydrangea macrophylla var. serrata types in zones 4 and 5. The following solutions have been tested successfully in Michigan and Maine’s northern interior since 1993. Don't prune unless necessary. Pruning often removes the flower buds. If you need to prune, remove any dead stems in the spring. Any other necessary pruning should take place immediately after bloom. The new flower buds form in autumn, when night temperatures consistently drop below 60 degrees. Cover the plants to a depth of at least 12-18 inches with mulch, bark, oak leaves, pine needles, or straw. Cover the entire plant, tips included, if possible. Remember not to use maple leaves because they will mat when wet and can suffocate the plant. Some people make cages out of snow fence or chicken wire to hold the mulch. One creative gentleman, who every year has a spectacular Hydrangea garden, uses 20 gallon plastic trash cans. He cuts off the bottoms, places them over his plants in early winter, fills them with mulch and then puts the lid on them until spring. . Remove the mulch only after any major threat of frost (50% frost-free date) has passed. For the Mid-West Michigan that is around May 15th. Do not be concerned if there are small white leaves and stems they will survive and turn green again quickly.