The lacy lavender and pink blooms of hydrangeas (Hydrangea macrophylla) make the plants popular choices for landscaping. The bushes can grow quite large, making them a good foundation planting. The flowers can be used in arrangements, and they also dry well. Hydrangeas are hardy to Zone 6 but should be protected any time temperatures fall into the single digits. Though hydrangea plants may come back after die-back due to freezing, hydrangea blooms form on the previous year's growth. A plant that freezes and comes back in the spring won't bloom in the summer.
Build a cage from chicken wire or net wire around the hydrangea. Tomato cages work for smaller plants, but large shrubs will require custom-made cages. Brace the wire with wooden stakes for added support to guard against collapse under the weight of snow.
Line the cage with burlap or cardboard. Don't use plastic. Material that will allow air through is needed. Put the material inside the wire so wind doesn't blow it away.
Fill in the cage with leaves or loose straw. Completely cover the hydrangea in leaves or straw to insulate the plants from the cold. Set aside an extra bag of leaves or straw in a garage or shed.
Check the cage periodically during the winter, particularly after a snow. If the insulation in the cage has settled, add more from the bag you saved.