Spacing will depend upon ultimate height and spread of the variety or species you’ve chosen. A cool, moisture-retentive, acid soil (pH 4.5 to 6.5), particularly one that contains a high percentage of organic matter to hold moisture, is best.
The location should, in addition, be protected against drying winds and winter afternoon sun. Rhododendrons are shallow rooted and should not be planted too deep: the heavier the soil, the shallower the planting. Do not fertilize at planting time.
Keep plants well-watered, even in dry periods in the fall – a coarse mulch, 2 to 3 inches deep, to retain moisture and keep the soil temperatures cool, is beneficial. This will also keep down weeds, eliminating the need to cultivate, which could pose a danger to shallow roots. Spent flowers should be removed.