Azaleas and Rhododendrons are not difficult to grow but have special cultural requirements.
- The soil should be acidic, organic, moist, fertile and well-drained. Each of these conditions is important to grow Azaleas and Rhododendrons successfully. If you have alkaline soil, grow Rhododendrons as container plants since reducing soil pH is not simple. In neutral pH soils, the plants will be unable to get sufficient iron and their leaves will become chlorotic.
Azaleas and Rhododendrons do not tolerate drought or wet soils (with a few exceptions).
- Choose a site with dappled shade in sheltered conditions. Avoid deep shade beneath other trees. Dwarf alpine species will tolerate full sun provided the soil is kept evenly moist. Most Rhododendrons will tolerate a more open site if sheltered from cold, dry winds. Plants not given protection from the wind often develop leaf scorch or splitting of the bark on the stems. Avoid frost pockets and sites exposed to early morning sun.
- Most Azaleas and Rhododendrons are purchased with soil around their roots in containers or "balled". To plant them properly, dig a hole slightly larger, but no deeper than the container or ball. Set the ball so it is 2 in. higher (5 cm) than the surrounding soil. Never plant Azaleas and Rhododendrons so deeply that their stem is covered deeper than it had been growing in the nursery. Water thoroughly after planting and firm the soil around the ball. There is little need for fertilizing at planting time.
- Azaleas and Rhododendrons need a heavy mulch to conserve moisture and minimize winter damage. Coarse materials such as partly decomposed oak leaves or pine needles are ideal. Oak shavings, hardwood chips or aged sawdust and sphagnum peatmoss may also be used satisfactorily. Use a mulch of sawdust or hardwood chips about 2 in. deep (5 cm). A mulch of oak leaves should be 4-6 in. deep (10-15 cm). Keep the mulch around the plants all year, but don't allow it to be too high on the plant stems during the summer and fall. In winter pile it higher to help prevent winter leaf scorch or bark splitting on the stems. A good heavy mulch has also the merit of keeping down weeds.
- Azaleas and Rhododendrons grow well naturally at fairly low nutrient levels. Therefore, fertilization should be done carefully to avoid their delicate roots to get damaged. A light application of a fertilizer formulated for acid-loving plants may be added to the surface, according to the directions on the package, before the mulch is applied. Fertilizing should be done in the spring and never later than midsummer. Late summer fertilization may force out tender fall growth that will be killed by the winter.
- Select companion plants that do not compete for moisture with your Rhododendrons and Azaleas or they will suffer - unless you live in a high rainfall area.