While these plants like the shade neighboring trees can provide, trees with shallow roots or that are densely covered with leaves, such as beech, birch, elm, maple, poplar, and sycamore, can compete for water or cast too much shade. Around these trees, plant just outside the drip line to avoid both competition from roots and too dense a canopy.
Soil is also key. Azaleas and rhododendrons do best in acidic soil. They also have the contradictory need for soil that can provide regular constant moisture while still draining well to prevent root rot. In addition, they prefer more air around their roots than most plants. To meet these requirements, be sure the soil is rich in organic matter; you may need to amend it before planting. If your soil is too heavy, clay-like, or alkaline, consider planting in a raised bed.
If planting a bare-root plant, first soak the roots for four hours. Dig a hole as you would for planting from a container. Form a mound in the center; the crown of the plant should sit about 1 inch above the adjacent soil.
Put the plant in place, checking that the height is right (fill in with soil if the plant is too low), and then spread the roots out around the mound. Holding the plant in place, add the soil that you dug up, firming as you go. When almost finished, gently water. If the plant settles, add additional soil beneath it to bring it back to the proper height. Finish filling in the hole, and then build a watering berm around it and water gently.
Next see: Caring for Azaleas and Rhododendrons