Azaleas – as far as gardeners are concerned – are a group of shrubs related to Rhododendrons within the Ericaceous family of plants. Botanically, azaleas are correctly known as rhododendrons. For the purpose of this section, azaleas are a specific category within the Rhododendron family, typified by small to medium leaves with masses of flowers in spring or early summer.
The can be a confusion out of the fact that some of the rhododendrons have even smaller leaves than the azaleas – notably Rhododendron ‘Blue Diamond’ and similar shrubs.
Azalea shrubs can be either deciduous or evergreen with some being fully hardy and others falling at the first frost. Most azaleas are low growing mound-forming shrubs having a spectacular show of flowers – sometimes scented – with a colour range from pure white through all shades of pink and mauve, and then darkest red on the evergreen types.
The deciduous azaleas have slightly more subtle colours – but no less spectacular – ranging from white through creams to rich golden yellow or orange, or from pink through to deepest red.
The Indian Azaleas are those evergreen types to be found in the florist shops – especially near to Christmas. The garden hardy evergreen azaleas are those broadly grouped as Japanese Azaleas.
Indian azaleas are often sold outside the shop – owing to lack of space and Christmas stock - or in open air markets. This can lead to their rapid demise for they are not hardy plants – even succumbing to chill winds or draughts. In tight bud, they can easily be mistaken for Japanese Azaleas, and therefore often planted outside after the indoor flowering period. If they do not die during the spring or summer after planting out, they will most certainly die with the onset of frosts in the first autumn.
The hardy evergreens for the garden are the Japanese Azaleas. Other than late frost sometimes spoiling the emerging flowers, the Japanese Azaleas are hardy in all but the coldest of positions. These form a dense canopy of foliage over time with a total covering of flowers in early to late spring.
Some are not fully evergreen and tend to lose a few leaves in autumn/ early winter. It is only a slight leaf drop – no need to panic, just enjoy the tint of the foliage before it drops.
The deciduous azaleas are more upright growing than their evergreen cousins – eventually forming a shrub up to 2 or 3 metres.
The foliage is often a spectacular display during autumn leaf fall. The flower bud clusters are then displayed at the ends of most branches – gradually swelling to burst into full flower in late spring – often scented.
The three main groups of the deciduous azaleas are known as ‘Ghent Hybrids’ of Belgian origin, which have a true Rhododendron in their parentage – R. luteum And are often scented; ‘Knap Hill’ or ‘Exbury Hybrids’ which were hybridized in the UK – either scented or not; and the ‘Mollis Hybrids’ of both Dutch and Belgian origin – rarely scented.