Azaleas and Rhododendrons
Site Selection and Planting
Choose a site protected from drying winds and excessive direct sunlight. An area with some high broken shade is ideal. Avoid planting too close to a building foundation, under a roof overhang, or under trees with dense shading.
Azaleas and rhododendrons grow well in a porous, well-drained, acid soil (pH 4.5-6.0). At least 25-50% of the mix should be made up of organic material such as pine bark soil conditioner or compost. When planting, dig the hole approximately twice as large as the container. Knock the plant out of the container and lightly loosen the roots if matted. Situate the plant so the top of the rootball is two or three inches above ground level. Never plant an inch or two deeper than the root ball, as is sometimes recommended for other plants. Back fill the hole with your prepared organic mix and water well.
After planting, a light covering of mulch, is beneficial but should not heavily cover the rootball nor should it make contact with the stems or trunk. Pine bark, pine needles, or any other organic material is suitable for mulch and these will help conserve moisture, moderate temperatures, and restrict growth of weeds. The fibrous roots of azaleas and rhododendrons grow close to the surface and should not be hoed or cultivated.
Fertilizing
A balanced acid fertilizer, often called Azalea-Rhododendron-Camellia fertilizer is ideal. Hollv-tone'" is an excellent organic fertilizer suitable for azaleas and rhododendrons. The best time to fertilize is in the spring just after flowering and again in late June for formation of next year’s flower buds. Spread the amount of fertilizer recommended on the label around the dripline, not near the stem. Be careful not to over-fertilize azaleas and rhododendrons as this can actually damage the plants. They are not heavy feeders, and often a good, rich compost as a mulch over the root area is sufficient.
Pruning
For azaleas a limited amount of pruning and shaping may be done, preferably in the spring immediately after flowering. On rhododendrons, pinching the single terminal shoot just as it starts to grow and elongate in the spring will encourage branching and produce a more compact plant. Gently snapping off the faded bloom trusses after blooming will also groom your plant and encourage more branching and vigor.
Pest and Disease Control
Pests are not a major problem, but like most plants, there are a few pests to look out for. One such pest is the lacebug, which causes the leaves to begin to take on a whitish or faded appearance. Close observation will reveal tiny stippling created by the insects as they suck the juices from the underside of the leaves. You may also see black tar-like spots on the leaf undersides and even the gray- beige triangular shaped insects themselves. Lacebug problems are worse for plants that are sited in full sun or afternoon sun.
Mites can also be found on azaleas causing the leaves to take on a bronze-tinted look. If you suspect either of these insects may be a problem, bring in a sample for diagnosis and recommended treatment. Both of these pests can cause considerable cosmetic damage to the plants as well as rob them of some of their vigor.
Rhododendrons are susceptable to a Twig Blight (Botryosphoeria) especially during warm, wet springs. It usually appears in late May as sudden wilt and dieback of random branches. Spray in March and after flowering with chlorothalonil (Daconil, Fung-oniI) or copper sulfate.
One of the most common problems associated with azaleas and rhododendrons is wet feet. They cannot tolerate being in a boggy area where the roots are always wet as this can cause root rot. Keep in mind, however, that they are-both shallow-rooted plants and, in the middle of summer when it is hot and dry, they will be some of the first plants in your yard to dry out and need water.