Rhododendrons and azaleas create beautiful spring color displays. Unfortunately, these plants have special requirements that may be difficult to maintain in the North.

Both types of plants are in the genus, Rhododendron. Generally, the plants we call rhododendrons flower at the tips of the branches while azaleas flower all along the stem. Some of the plants are deciduous and others are broadleaf evergreens.

Climate is a big factor in the success of these plants. Many varieties are not hardy for our winters. Be sure to plant only those types known to be hardy in USDA Zone 5 or lower. We cannot grow many of the beautiful, large specimens found in the Pacific Northwest or in the Carolinas.

In addition to extreme cold, winter winds are very damaging to the evergreen types. Rhododendrons tend to be shallow rooted. When the ground freezes, they cannot take up water. Cold, dry winter winds sweeping over the leaves draws moisture out rapidly. Since the roots cannot replenish the supply, the leaves shrivel. If they dry out too much before a warm spell, they will die.

Hot summer sun beating on the plants is also undesirable. Rhododendrons need to be in a somewhat shaded location with dappled light exposure. They do not like deep shade.

Rhododendrons and azaleas do best in an acid soil. The pH needs to be below 6.0 and the range of 4.5 to 5.5 is ideal. Sulfur products and organic material such as sphaghnum peat or oak leaf mulch may help lower the acidity. If the pH is too high, the leaves will have a pale color and the plant will not be vigorous.

Drainage is a must for these plants. They do not do well in heavy, clay type soils where water stands after rains. Some experts feel that good drainage make be even more important than soil pH for long-term survival.

Nitrogen for these plants must be provided in the ammonium form rather than the usual nitrate form found in most fertilizers. Ammonium sulfate (NOT ALUMINUM SULFATE) is an excellent nitrogen source because the sulfate will also help keep the soil acid.

For a higher chance of success with rhododendrons, plant hardy varieties, give them shelter from winter winds, keep them watered, provide good drainage, keep the soil acidity in balance and use the ammonium form of fertilizer. It sounds like a lot of work but the rewards can be great.