Rhododendrons require fairly acidic and wet, but well-drained soils. They like cooler sites and do not tolerate very sunny spots. Therefore, do not:
1) Plant rhododendron (or its associate, mountain laurel) close to the house on the south or west side (where they will receive intense sunlight and the walls will emit radiant heat into the night). Plant on the eastern and northern sides of your house (wetter, cooler, less sun).
2) Plant in clay soils; if you do have clay soils, amend with peat moss (increases organic matter and decreases pH).
Additionally, rhododendrons prefer an acidic soil (pH of between 5 and 6). Having a soil test done will let you know if you need to amend your soil for optimal plant growth. Contact your local Cooperative Extension office for information on soil tests in your area.
