Although plant care for azaleas and rhododendrons isn't as challenging as their taxonomy (see Page 2), you still need to know what steps to take to promote optimal health. On Page 4 we'll consider such matters as pruning azaleas and rhododendrons, but I'll begin here with tips on planting azaleas and rhododendrons.
First Rule in Care for Azaleas and Rhododendrons: Location, Location, Location
Planting azaleas and rhododendrons in a spot cooled by partial shade, where the soil is acidic and well-drained, is a step in the right direction in the proper care for azaleas and rhododendrons. Despite being known as shrubs that grow in shade (dappled shade, preferably), some varieties will tolerate full sun if sufficient water is provided. For example, I grow the Stewartstonian type in a spot where it receives a lot of sun in the morning, midday and late afternoon, yet with adequate water it performs just fine.
Soil pH should be about 5.5; have your garden soil tested first before planting azaleas and rhododendrons. An overly alkaline soil can be corrected by applying fertilizers for "acid-loving" plants, such as blueberries and azaleas. These specialty fertilizers will contain ammonium-N, which will lower soil pH.
Basics of Planting Azaleas and Rhododendrons: Soil
A good tactic for providing the necessary drainage is planting azaleas and rhododendrons in raised garden beds. Amend the soil with decomposed sawdust or pine bark (both are acidic), or apply garden compost. The recommended planting time for balled-and-burlapped plants is late fall or early spring. In either case, water well after planting azaleas and rhododendrons. Don't apply fertilizer at the time of planting; new foliage and roots aren't yet ready to handle the high salt content of fertilizer, and they can be burnt.
Shady Companion for Azaleas and Rhododendrons: Red Oak Trees
Since azaleas and rhododendrons prefer shade, it behooves landscapers to choose a good shade tree to have growing near them. Will just any shade tree do? No! Azalea and rhododendron plants like acid soil and have shallow roots. A shade tree compatible with them will not mind acid soil and will not have shallow roots. For if the shade tree, like the azaleas and rhododendrons, has shallow roots, it will be in competition with your bushes.
Henning's Rhododendron and Azalea Pages, an excellent information source on these plants, suggests a few shade trees compatible with azaleas and rhododendrons, among them being the red oak (Quercus rubra). The Henning’s site reports that the red oak is a fast grower, eventually reaching a height of 60’-75’ with a spread of 40’-50’. The red color of its autumn leaves makes it a fine fall foliage plant. In addition, the red oak is pollution-tolerant, an important consideration in urban and suburban landscaping.
On Page 4 we consider more issues regarding the care of azalea and rhododendron plants: fertilizing, mulching and pruning azaleas and rhododendrons....