Ericaceous plants such as evergreen Azaleas and Rhododendrons are native to Asia, where Azaleas are the national flower of Nepal, although both can also be found in the Appalachian Mountains of North America, so essentially hilly areas with well-drained, acidic soil.
They were discovered in the 16th century although did not come to prominence until the mid-18th century and although all Azaleas as small to medium sized shrubs are actually Rhododendrons, not all Rhododendrons, which range from medium shrubs to trees, are Azaleas.
Rarely exceeding 1 metre in height the small leaved Azaleas, originally cultivated by the monks of Buddhist monasteries, produce an amazing show of flowers in May ranging from the frilly edged white blooms of Adonis to the pink and light purple hues of Blaauws Pink and Amoena respectively and the deep vermillion red of Addy Werry to name but a few and are suited to planting in beds and borders as well as woodland gardens and containers.
The larger growing Rhododendrons, whose name comes from the Greek rodon meaning rose and dendron meaning tree and reaching approximately 180cm by 180cm, are unsurpassed for the beauty of their large blousy flower trusses and are equally at home in the dappled (not dense) shade of woodland plantings or in full sun.
They are ideal as specimens or for mass plantings where space allows and as informal hedges. As with Azaleas the colours are many and varied ranging from the Cunningham White which is pale mauve fading to white with yellow, brown and purple spots or Madame Masson, white trusses with a yellow basal blotch, to the pinks of Anna Rose Whitney, Cosmopolitan, Germania and Rocket, the yellow of Horizon Monarch and orange of Virginia Richards and the deeper red and purple shades of Albert Schweitzer, Halfdan Lem, Lord Roberts and Lees Dark Purple. These are only a few examples through the colour spectrum so plenty to select from dependent upon the garden design.
Rarely succumbing to pests or diseases, if planted in suitable soil no more than 30cm deep as the roots only extend normally to that measure and any deeper would deprive them of air, Rhododendrons need little pruning only to remove dead or damaged branches or after flowering to reduce height.