The magnificent blooms of rhododendrons and azaleas do more to announce the arrival of spring than almost any other flowering plant. Both are members of the same plant group, and both add a lively touch to your landscape.
Azaleas and rhododendrons grow well in filtered or moderate shade, preferably where there is alternating sunshine and shade, such as under deep-rooted trees or near buildings. Generally, they do best on the north and east side of your home where they will be protected from the hot afternoon sun. While azaleas will sometimes adapt to full sun, they are usually inferior in their growth and flowering. They are also more prone to insect and disease problems.
Both of these beautiful shrubs should be planted in early spring or autumn through late winter. They can be transplanted even when they are blooming, but very special care must be taken to keep them from drying out. Plan your site according to the fully mature size of the plants. The spacing for most azaleas should be four to five feet apart. Rhododendrons grow larger and should be planted six to eight feet apart.
1. Turn the pot on its side and apply foot pressure to loosen the plant from its pot. Never try to pull azaleas from their pots by pulling on the trunk as it may break off its roots.
2. Loosen the fibrous root ball with a knife or a hand cultivator.
3. Dig individual holes for each plant twice as wide as the root ball and no deeper than the root ball.
4. Set the plant in the center of the hole with the top of the root ball one to two inches higher than ground level.
5. Back fill the hole with soil, snugly packing it around the roots to eliminate air pockets.
6. Soak the soil thoroughly with water and plant starter solution.
7. Note that in 1981 the American Rhododendron Society stopped recommending the use of peat moss when planting azaleas and rhododendrons because the addition of soil amendments to individual planting holes is detrimental to plant growth and development.
Azaleas and rhododendrons require about the equivalent of an inch of rainfall every ten days in hot weather. During dry spells, soak them thoroughly every seven to ten days. Be sure water reaches all the way down to the bottom roots. Being evergreen, they will need watering in winter during warm dry periods to prevent winter injury. Rhododendrons and azaleas are very susceptible to root rot if planted in areas of poor drainage. Be sure the plants are not kept too wet.
Neither of these plants require pruning except to remove dead growth or to shape them. This should be done after the blossoms have fallen and before mid to late June. Removal of spent rhododendrons will help promote flowering the following year.
Immediately after bloom is the best time to fertilize. At Snow's, we recommend Holly-tone, a slow-release, granular fertilizer for acid-loving plants. It should be used according to label directions. Mix the fertilizer in well with the mulch or soil around the plant's perimeter, being careful not to disturb the plant's delicate surface roots. A November feeding at half the spring feeding rate is also recommended.
Add new mulching material every spring. Generally, pine needles, shredded bark, oak leaves, or leaf mold, about two inches thick, will provide a good mulch for your azaleas and rhododendrons.