Rhododendrons are a genus of flowering trees that contains between 500 and 800 distinct species, including azaleas. Bonsai is the art of keeping small trees in pots that reflect qualities found in much older, larger trees. Most rhododendron bonsai are created using one of many species of azalea.
Two varieties are very common for bonsai cultivation in Japan. The Rhododendron indicum and the Rhododendron simsii are often referred to as Satsuki azaleas. These trees are low growing and have unscented flowers in a number of colors, including white, pink, red and purple. Unlike other species, Satsuki azaleas flower in the summer rather than the spring. One variety of Satsuki is the Kaho azaleas. This variety is unusual in its mid-winter flowering. Kaho azaleas feature large pale pink trumpet shaped flower.
Kurumes are a hybrid of Rhododendron kaempferi and Rhododendron kiusianum. This variety is much hardier than Satsuki azaleas and has very small funnel-shaped flowers in the spring. This variety's diminutive flowers make it ideal for smaller bonsai.
To keep your rhododendron or azalea healthy and flowering, remove dying flowers and leaves immediately. Removing dead or dying flowers will encourage healthy growth and help to prevent disease.
Prune new growth from your rhododendron bonsai as soon as it is finished flowering. Prune secondary shoots again in midsummer. Prune your bonsai by clipping growth either at the branch collar or next to a blossom or leaf bud.
In addition to pruning, you can wire your rhododendron to help direct its shape. To wire your tree, use only aluminum or copper bonsai wire. Wrap the wire at approximately a 45-degree angle to the direction of growth of the branch. Once wrapped, gently bend the branch to the new growth direction and leave the wire in place for several months. After several months, cut the wire off and check the position. Minor changes in shape may take after two or three months, but more severe changes in direction may require a second wiring.