Rhododendron species/Azalea Species Guide
The Rhododendron genus is massive and includes anything between 500-900 species depending on which authority you consider. In terms of bonsai, it is small-leaved species that are suitable; these tend to be Azaleas.
The two principal Azalea species for bonsai are Satsuki azaleas and Kurume azaleas. The main attraction of the Azalea are the flowers that appear in late Spring or early Summer.
Azaleas are easily found in all UK tree and garden nurseries, however, it is very difficult to locate specimens with thick enough trunks for bonsai and such trees will be expensive.
Ease of Cultivation 5/10 Ease and Suitablity for Bonsai Styling 3/10
Rhododendron/Azalea are intolerant of lime and hard water.
Position Rhododendrons dislike full sun and strong light can quickly fade and ruin flowers. Place in partial shade or dappled sunlight.
Rhododendrons have varying abilities to withstand frost, some species are able to withstand extremely low temperatures while others such as Satsukis are relatively frost-tender. Frost hardiness is very much down to individual hybrids and unless an individual specimen is known to be hardy to a certain temperature, it is worth providing good frost protection as soon as Winter arrives.
Watering In hard-water areas trees must be watered with
rainwater only to avoid lime deposits building up in the soil.
Repotting Repot as soon as flowering has finished annually or when roots fill pot. A lime-free soil mix MUST be used. Must be planted in ericaceous/acidic soil.
Pruning Azaleas/Rhododendrons are basally dominant which means they grow more strongly at the base and sides than at the top; for this reason they should be pruned harder at the bottom and sides than the top.
Azaleas respond well to hard pruning and if pruned back to a stump after flowering will bud-back prolifically (assuming good health).
Propagation From softwood cuttings in early Summer, air-layering/ground layering in early Summer after flowering has finished.
Pests and diseases Whiteflies, scale insects, caterpillars, aphids, mildew, budblast, rust, leaf gall, petal blight and lime-induced chlorosis (if soil not acidic enough). Never spray open flowers with insecticides or fungicides as this will cause them to wilt and fall.
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