Soil Needs
Soil pH should be about 5.5. Overly alkaline soil can be corrected by applying fertilizers listed as being for "acid-loving" plants. These specialty fertilizers contain ammonium-N, which lowers soil pH.
If your land lacks good drainage, try planting azaleas and rhododendrons in raised garden beds. Amend the soil with compost. Install plants in late fall or early spring. In either case, water well after planting azaleas and rhododendrons.
We recommend Foxfarm's CULTIVATION NATION® PH DOWN
Lowers Nutrient Solution pH
It’s time to get down! Use Cultivation Nation® pH DOWN to lower the pH of your nutrient solution in both soil and hydroponic environments.
Fertilizer Needs
Do not apply fertilizer at planting time. New foliage and roots are not yet ready to handle the high salt content of fertilizer, and they can be burned by the fertilizer. A good time to fertilize azaleas and rhododendrons is right after the plants have finished blooming.
There are standard fertilizers to use on azalea and rhododendrons bushes, mixes that can be purchased at nurseries and major hardware chains. Be careful not to over fertilize. Follow the instructions on the fertilizer's label, except for the amount of fertilizer to apply. Cut that in half. It is usually better to be conservative about applying fertilizer so that you do not risk burning your plants.
We recommend Foxfarm's HAPPY FROG® ACID LOVING PLANTS FERTILIZER
Designed For Low pH Lovers 4 - 5 - 3
Happy Frog® Acid Loving Plants Fertilizer is specifically formulated for use on azaleas, rhododendrons, camellias, hydrangeas, evergreens, blueberries, raspberries, strawberries, and all other acid loving plants.
Mulch
Mulching is an essential part of proper care for azalea bushes and rhododendrons. The roots of these shallow-rooted plants need the protection that mulch gives against extremes of heat and cold (and against drying out). Azaleas and rhododendrons like well-drained soil, not dry soil. Azaleas and rhododendrons are not desert plants; they like water. The plants do not like to be sitting in it for long periods of time, which would cause their roots to rot.
The best mulches for azaleas and rhododendrons are acidic mulches, such as pine straw.
Pruning
Prune azaleas and rhododendrons immediately after the bloom period is over (generally early summer in zone 8) . Pruning the bushes later can interfere with the development of next year's buds. Begin by pruning off dead or injured branches, which could cause disease and insect problems in the future. Then prune back tall, gangling limbs shooting out of the top of the bush. This will promote a more attractive, compact shape.