Choosing rhododendrons is largely matter of deciding on size, flowers, foliage and flowering season, while always considering your growing conditions. Sometimes other aspects may also be important. For instance, you may want fragrance or a special growth form, but mainly it is size, color and foliage that matter most. Deciding on the size of plant is not just a matter of knowing its height and spread; the general growth habit is equally important. Densely foliaged plants often look better than open growers but open plants allow light to penetrate and allow the planting of woodland perennials and small shrubs near them. Consider the overall effect -height, width and foliage cover -when deciding if a plant is suitable.
Even the most spectacular rhododendron's flowers are only open for a relatively brief time. In terms of year-round appearance, the foliage is far more important than the flowers. Rhododendron foliage is every bit as variable as the flowers and can be just as beautiful too, so take the time to consider the foliage when choosing your plants. Of course, it is hard to ignore the foliage unless you are buying a deciduous azalea out of leaf but it is surprising how often poor foliage is ignored for the sake of a month of pretty flowers.
Some rhododendrons have aromatic foliage. This may not be noticeable unless the foliage is crushed, but on damp or warm days the scent, often cinnamon-like, can be quite strong. Rhododendron campylogynum, R. cinnabarinum, R. glaucophyllum and R. hippophaeoides have noticeably aromatic foliage.
A few rhododendrons have attractive reddish brown, peeling bark. It is rarely a feature to rival their flowers or foliage, but it is an extra, adding to the appeal of plants that might otherwise look rather drab in winter. Rhododendron barbatum, R. cinnabarinum, R. hodgsonii and R. thomsonii have interesting bark, and R. arboreum has distinctive gnarled bark that sometimes peels to reveal a reddish undersurface.