Azaleas (Rhododendron spp.), which include both evergreen and deciduous varieties, may flower at any time from spring through summer, depending on the cultivar. Azaleas grow in U.S. Department of Agriculture plant hardiness zones 4 through 9, depending on the specific variety. Moving and transplanting an existing plant or a new nursery plant at the right time helps ensure continued healthy growth and abundant blossoms.
The Right Time
Although you can transplant new azaleas at any time of year, fall is the best time because the shrubs have time to establish a healthy root system before being exposed to summer heat the following year. If you are moving and transplanting an existing azalea from the garden, do so in winter when the plant is still dormant. Dormant plants suffer less transplant shock and the roots will establish when growth resumes in spring.
Choose Your Spot
A spot in dappled shade with well-draining soil is the right place for an azalea plant. The mature size of the azalea depends on the variety, so make sure the site provides enough room for the shrub to reach its full size without crowding from buildings or other plants. Azaleas require a soil pH 4.5 to 5.5, which you can determine through a soil test. If the pH is too high, lower it with a sulfur amendment. It's unlikely you need to raise the soil's pH for azaleas. For example, soil with a neutral pH of 7.0 requires 1 1/2 pounds of aluminum sulfate per 10 square feet to lower it to a pH of 5.5. Before you plant, till any necessary pH amendments and a 5-inch layer of compost into the top 12 inches of soil.
Cutting back existing azaleas to 6 inches tall before you dig them in winter forces them to develop healthy roots before they divert energy to the foliage and stems. Wipe the shears with a rubbing alcohol-soaked rag before you cut into the plant to avoid transferring diseases and pests. Loosen the soil around the roots to an 18- to 24-inch depth, and then lever the root system out of the ground with a spade. If any roots appear dead or damaged, prune them off with the disinfected shears before transplanting. Pot-grown azaleas only need to be removed from their pots, but they may be root-bound. If you see roots encircling the entire root ball, slice through the root with a disinfected knife before you plant.
Transplant With Care
Both newly lifted and pot-grown azaleas require the same transplanting care. The planting hole should be the same depth as the root ball or nursery pot, but two or three times as wide. Set the azalea in the hole, gently spreading out the roots, so the plant is at the same depth as it was in its former location. After filling in the hole with soil, water until the soil settles and is moist throughout the root zone. Mulching with a 2-inch layer of pine bark right after transplanting helps keep the soil moist, but pull the bark back so it doesn't rest against the azalea's trunk. Water the newly transplanted azalea two to three times a week for the first two months after planting. Apply about 1 inch of water at each watering.