Azalea Problems and Proper Care

Azalea Care

Brian Jervis: Ask a Master Gardener

Sunday, July 22, 2018

Q: I have azalea bushes that are so beautiful in the spring but then develop problems over the summer. Should I just live with these issues or is there something I can do to help make them look better through the summer? Michelle T., Broken Arrow

A: Landscapes bursting with healthy plants give us splashes of color that change with the seasons, and azaleas are ideal centerpieces for flowering shrub beds, containers and even hedges.

However, the dream of such garden beauty sometimes comes into question when spots and holes appear in leaves, the foliage turns yellow or flower buds remain closed. While azaleas can withstand many of the insect and disease problems that plague other plants, there are still a few problems that can occur.

First of all, plant in the right location (east facing with good morning sun is the best), with good drainage and air circulation between plants to help prevent problems. However, when that is not sufficient, here are a few of the most common offenders:

Aphids: These may appear on the stems of any plant when the weather is humid and plants are too close together without enough air circulation. Treat aphids with a hard spray of water from the hose.

Lace bugs/spider mites: Azalea lace bugs make up about 90 percent of all azalea pest problems. They feed on leaves, creating speckled areas on the leaf surface. Spider mites cause white stippling on leaves first, but then the area turns a rust or gray color. Both can be treated with insecticidal soap, horticultural oils or a systemic insecticide that includes the ingredient imidacloprid. Use it as a soil drench once yearly after blooming to avoid harming bees.

Fungus-related issues: Leaf galls, rust, petal blight and leaf spot are caused by fungus. Petal blight appears as tiny white spots on flowers. Leaf spot manifests as brown blotches that grow in size. Treat with a fungicide.

Root rot/water mold: Azaleas may also be impacted by another fungus that causes root rot, sometimes called water mold. Azaleas that stand in water during warm weather are particularly susceptible. This occurs mostly when azaleas are planted as a foundation plant near a down spout. This fungus spreads fast, so watch for yellowing leaves and wilting plants.

Iron Chlorosis: Azaleas prefer acidic soils. If not planted in such, leaves will turn yellow. With this condition, a soil test is always in order, which can confirm the actual soil pH.

To assist in preventing these issues, azaleas should be mulched with several inches of pine bark, and some of the bark should be incorporated directly into the planting soil to help add oxygen and ensure thorough drainage.

Protect your valuable and beloved plants with regular attention, looking carefully for potential problems along stems and branches, as well as under leaves. And, when it comes to chemicals, more is never better. Small infections and infestations may go unnoticed, only to grow into larger issues later. Therefore, it is best to examine your azaleas every time you water.

For more information and assistance with azaleas, drop by the Tulsa County Extension Office or call the Master Gardener hotline at 918-746-3701 to speak with a Tulsa Master Gardener.

Garden tips

·        When watering your lawn, ornamentals or vegetables, always do so in the morning, if possible. If watered in the evening, plants will go into the night still moist. Most disease-causing organisms need moisture and, because they grow best at night, leaving leaves wet in the evening will promote many plant diseases.

·        Bulb onions are ready to harvest when the tops fall over. They should be removed and allowed to dry in a well-ventilated, shaded area. After the tops are completely dry, they may be stored in a cool, dry area.

·        Tomato production stops in the heat of the summer. Most tomato pollen becomes infertile and blossoms drop off when the night temperatures are above 70 degrees and daytime temperatures are above 92 degrees for a few days. Tall, spindly tomato plants with scarce fruit are usually due to either too much nitrogen fertilizer or too much shade. If this occurs, cut them back by ⅓. New growth and fertile blossoms will develop when it cools in the fall.