Proper soil preparation, planting method and site location are crucial for growing azaleas where it snows. Azaleas have shallow, tender roots. As long as the roots are protected and dry during the first few hard frosts, they will winter over without trouble. Protection from winter sun is equally important. The plant must go dormant during the winter. If the azalea gets winter sun it will try to put out new growth while the roots are dormant, stressing and damaging the plant. Plant azaleas in the spring or early summer to give the pant a full growing season before the first cold weather.
Plant azaleas where they will be protected from winter sun and harsh winds. Dig a 6-inch deep post hole to check the drainage. Fill the hole with water. Plant in a different site or consider a raised bed if water remains in the hole after four or five hours.
Dig out a planting hole in the center of the planting area 30 inches wide and as deep as the rootball of the azalea. Break up the soil in the bottom of the hole with a garden fork or shovel. Build a raised bed or planting mound 30 inches wide and 12 inches high in areas where the drainage is poor.
Mix 2 parts rotted leaves or ground pine bark, 1 part coarse sand and 1 part compost. Mix half the soil from the planting hole with the mixture of organic matter. Mix 2 parts potting soil, 1 part ground pine bark or rotten leaves and 1 part coarse sand for a raised bed or planting mound.
Turn the potted azalea on its side and gently slide it from the nursery pot. Grasp the base of the trunk and gently work it free if it resists. Place the rootball into the hole so that the base of the stem is 2 to 3 inches above the soil level. Fill in the soil under and around the roots and build the soil up to the base of the stem, creating a 2- to 3-inch slope away from the trunk.
Spread a 4-inch layer of pine bark mulch over the planting area, but keep the mulch 3 to 4 inches from the base of the stem. Apply 1 inch of water weekly during the summer to keep the soil damp. Discontinue watering 1 month before the first frost date to let the roots go dormant.
Build up the mulch until it is 6 to 8 inches deep and pile it against the azalea trunk for added cold protection. Apply the additional mulch one to two weeks before the first hard frost. Construct wind protection around the azalea. Build a temporary fence or lean pine tree branches over the branches and around the trunk.
Apply 1 gallon of water to the soil around the roots after the first three to four hard frosts. Cease watering until spring.