Azaleas are a signature plant in southern spring and also in southern gardens.
Interestingly, North American native azaleas are all deciduous species. Most of the azaleas in our yards, however, are evergreen, with their ancient roots in Asia. The result is more than 10,000 registered or named varieties from hundreds of years of breeding.
As southern gardeners we are particularly aware of azaleas during the spring. Consequently it is a good time to look at caring for them.
Here are 18 things to know and do so our azaleas will thrive:
• Plant azaleas in early spring or fall; new roots need time to develop before summer heat and drought.
• Keep transplanted azaleas well watered, but not water-logged, until they are established.
• Azaleas grow best in dappled or part shade. Deep shade produces spindly plants with fewer blooms. Too much sun results in shorter bloom time.
• Plants require acidic soil with a pH of 4.5-6.0.
• Soil should be loose, well drained and contain plenty of organic material.
• Plant the root ball higher than ground level.
• Azaleas have a shallow root system that spreads within the top 12 inches of soil. Protect roots with organic mulch beyond the drip line, but leave bare two inches around the stem.
• Fertilizer is usually not necessary. It can burn shallow roots. Azaleas get adequate nutrition as mulch and compost slowly decompose.
• Chlorosis (yellowing leaves with green veins) and stunted growth are likely indicators of nutrient deficiency. If a soil test shows a nutrient deficiency apply a scant amount of slow release fertilizer for acid loving plants.
• Too much water, too little water, or too much fertilizer can cause brown leaf tips and leaf drop.
• Prune azaleas when they have finished flowering, and before mid June. If you prune after that you reduce next year’s blooms.
• Cut leggy stems back to the place where they meet a larger branch.
• A cool damp spring can lead to petal blight, an airborne fungus. Flowers appear spotted and turn brown. They look mushy and water logged, sticking to the leaves. The fungus over winters on the fallen blossoms. Remove and destroy dead blossoms from your plants and the ground around them.
• Leaf gall is a fleshy fungal growth that begins shiny green. White spores cover then cover the mass which dries brown. Pick off, bag and throw out the growths, ideally before the spores are released to become new galls next spring.
• Azalea lace bugs can be a problem – their population continues to increase if they are untreated. Look for small black specs on the underside of leaves. Their sucking sap causes a stippled effect on the surface of leaves turning them from green to grayish. Lace bugs overwinter on plants as eggs. Spray plants thoroughly with horticultural or control lace bugs chemically with Sevin, malathion, cyfluthrin and imidacloprid products. Follow label instructions.
• Red spider mites start on the underside of leaves. They look like tiny specs. As the population increases they move to leaf surfaces. Look for fine webbing on leaves to help identify the pests. Horticultural oil will help control the numbers, but a chemical miticide will be more effective. Always follow label instructions.
• Azalea caterpillars are small. They grow from about 1/2-inch to 2 inches long beginning brownish black with yellow and white stripes. They mature black with yellow and white stripes and a red head. Typically they feed in groups and devour leaves quickly. Look for the caterpillars during August and September. Use Bacillus thuringiensis, horticultural oil, malathion, Sevin, or cyfluthrin products to control them. As usual follow label instructions.
• Check the bark on plants, especially crotch areas, for azalea bark scale. Scale insects are damaging because they suck the sap out of plants. Scrape off scale insects as possible. Use horticultural oil to kill adults and eggs. (Insecticidal sprays kill only the crawler stage of scale.) Follow label instructions. Be aware that you will need to spray multiple times to control the pest.
Azaleas are beautiful and easy to grow. Just give them the right conditions and know how to trouble shoot a few problems.
Reach DEBBIE MENCHEK, a Clemson Master Gardener, at dmgha3@aol.com.
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