When training an azalea (Rhododendron spp.) as a bonsai, it is important to select a plant 2 to 3 years old with roots radiating from a heavy trunk base that tapers toward the top. Plants with branches radiating in all directions will be easiest to train. Satsuki hybrid azaleas, such as the "Kinpai" azalea (Rhododendron "Kinpai"), which grows in U.S. Department of Agriculture plant hardiness zones 7 through 9, work well as bonsai.
Find a Home
Grow bonsai azaleas outdoors because they will not live long-term as houseplants. Most azaleas grow in USDA zones 4 through 9, depending on the variety. It is healthiest for bonsai to stay outdoors year-round, but in cooler climates you can overwinter them in a cool room indoors or in a cold frame. The special containers for most bonsai are shallow, but all need to have drainage holes. If the drainage hole is large, cover the inside with a piece of screen to keep the soil from washing away. Water your bonsai regularly to keep the soil moist but not soggy. Water before freezing temperatures hit, but not while the root ball is frozen.
Digging in the Dirt
Mix fertilizer for bonsai azaleas by combining 6 parts cottonseed meal, 2 parts bone meal, and 1 part blood meal. Apply at a rate of 1 teaspoon per plant, diluted in the regular amount of water for watering, once a month in March, April, July and August. This fertilizer mix can also be used as an ingredient in bonsai soil. Mix soil using 2 1/2 quarts perlite, 1 quart calcined clay, 1 quart sphagnum peat moss and 5 1/2 quarts composted ground pine bark. To use for azaleas, add 1/2 tablespoon each gypsum and dolomitic limestone, 2 1/2 tablespoons composted cow manure and 1 1/2 tablespoon prepared fertilizer.
Healthy and Happy
Inspect bonsai azaleas frequently for pests. Azalea lace bug (Stephanitis pyrioides), azalea mite (Eotetranychus clitus) and southern red mite (Oligonychus ilicis) are common pests treated by completely covering the leaf surfaces with insecticidal soap. Dilute concentrated soaps at a rate of 16 teaspoons per 1 gallon of water, and spray in the evening when the temperature is between 45 and 85 degrees Fahrenheit. The risk of root diseases is minimized in well drained pots, but azaleas can still suffer from fungal disease like petal blight (Ovulinia azaleae) and Cercospora leaf spot (Cercospora handelii). Treat these by mixing a chlorothalonil fungicide at a rate of 2 1/4 teaspoons per 1 gallon of water in a spray bottle and spraying to thoroughly cover the plant. When using garden chemicals, wear long pants, a long-sleeved shirt and eye protection and use only on a calm day. Keep children and pets away from the area until the leaves have dried.
Choose a basic shape for the bonsai, such as formal upright or double trunk, after you've researched styles and assessed your azalea's basic form. Then, begin pruning the plant to eliminate dead or weak branches, and branches that do not fit the desired shape. Remember to wipe pruning tools with a cloth soaked in rubbing alcohol before and after use. To train the trunk and branches into a particular shape, wrap them with aluminum wire in spirals at a 45-degree angle and bend them gently into the shape you want. The wires should be snug against the trunk or branch but not pinching it. Rewire every three to six months as the wires become too tight. Each year, remove the bonsai from its container and prune one-third of the root mass. After the root pruning, clean the container and re-pot the plant with fresh soil.
- Journal American Rhododendron Society: Azalea/Rhododendron Bonsai
- Virginia Cooperative Extension: The Art of Bonsai
- Texas A&M AgriLife Extension: Bonsai
- Fine Gardening: Genus -- Azalea
- Clemson Cooperative Extension: Azalea & Rhododendron Insect Pests
- Clemson Cooperative Extension: Azalea & Rhododendron Diseases
- Cornell Cooperative Extension: Cold Frames & Hot Beds
- Monrovia: Kinpai Azalea
- Photo Credit Redcup2/iStock/Getty Images
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