Rhododendrons are an easy to care for, versatile, and beautiful plant that flourishes in many different climates. Although there is some debate as to the existence of a "true" blue in the rhododendron genus, there are several popular lilac or purple-blue varieties, such as: Blue Diamond, Bluenose, and Augustinii. These varieties have their own particular care instructions, but do not require more maintenance than your average rhody.
All rhododendrons prefer a well-draining, acidic soil. They should be planted high and in partial shade. Evergreen rhododendrons such as the bluish varieties mentioned do best in cooler climates of zone 6 to 9. They particularly thrive in the Pacific Northwest and the Appalachian areas. The Bluenose variety may be able to handle heat and cold extremes better than the other blue varieties.
Once established, the plant requires little maintenance. During the first year, make sure the plant is watered regularly. The roots grow slower than most other plants, so it needs a lot of water to prevent the root ball from drying out. You may need to mist the foliage during the warm summer months if the leaves show sign of wilting.
It is a good idea to spread organic mulch around the base of the plant. This will prevent the soil from drying too quickly and protect the shallow-growing roots of your rhododendron. The mulch will also keep down the amount of weeds. You do not want to cultivate near the rhododendron because you may damage the roots.
The blue, evergreen varieties of rhododendron are a shrub that can grow very large. While it is not necessary to prune, if your plant gets too large, prune before summer but after the plant has bloomed. This will decrease the likelihood that you will remove next year's blooms.