Originally created 05/04/01

Pruning too late in season can stop blooms on azaleas



Q: I have some large azaleas in my yard that did not bloom this spring. I also have leaves turning brown on some of the plants. Can you help me with these problems?

A: By far the most common reason azaleas don't bloom is that they were pruned last year during or after July. Azaleas begin setting buds for next year's flowers in July, a process that continues through the summer.

Prune azaleas after the spring flowers have faded and before the end of June. This will provide enough time for new growth to mature and harden off for winter and for flower buds to form.

Avoid cutting back your azaleas too severely. Often after severe cutback, all the energy of a plant goes into foliage production, which may inhibit flowering.

If pruning was not the problem, you could have a nutrient imbalance. Plants overfertilized with nitrogen tend to produce a flush of green growth and fewer flowers. You may want to take a soil test to determine the pH and other nutrient levels.

There are several possible causes for the leaf browning. Are the tips of the leaves browning first and slowly working in on the leaves, or are whole leaves browning at once?

Are all of the leaves on a stem browning? Follow the stem down toward the base of the plant and see if you have any cracked or split stems. If this is the case, you may have some winter injury.

Then the only thing you can do is to cut out the damaged stems close to the ground, making your cut just below where there is healthy stem tissue.

We may see a lot of this injury this year because of the cold winter weather and because we experienced late frosts this spring.

Azaleas in direct sun typically experience cold damage more often because of the heat buildup during the day and the cold during the night. Some the winter injury doesn't even show up until the summer, when plants are stressed.

Leaf browning can also stem from fertilizer burn, chemical damage, overwatering or underwatering. Check for all these possibilities and use the process of elimination to determine the source of your woes.

Other azalea problems

Azalea leaf gall is another common problem. The fungus causes new, developing leaves to become thickened, fleshy and distorted. The disease does not affect older leaves, which are resistant to the infection.

Initially, the thickenings are whitish or light green. As the spots enlarge, they become white or pink, with a powdery appearance. Later in the season, the distorted leaves turn dark and hard.

This problem is usually more severe in spring, during cool, moist weather, and where plants are growing in areas of poor air circulation or in full shade.

As the buds open in spring, fungal spores blown by wind to the plant or washed by rain from the bark enter the tissue. The spores need moisture to germinate. After infection takes place, a growth-promoting substance is triggered in the plant, causing the thickening and distortion.

The best control for gall is to remove it when it is first noticed, before it turns white. After that, spores are released that can infect azaleas again next year. Throw infected leaves in a plastic bag and put them in the garbage.

Once the azalea gets leaf gall it is too late for any spray control. As a preventive measure, you can apply fungicides before and as the leaf buds open and expand in early spring. The best fungicide products contain chlorothalonil and triadimefon.

You also need to be on the lookout for azalea lace bugs. The adults are Å inch long with transparent wings that are held flat on the back. Their wings are lacy, with two grayish-brown cross bands connected in the middle. Nymphs are mostly black and spiny.

The flask-shaped eggs are partially embedded in leaf tissue and often are covered with a black tarlike excretion. They feed on the underside of the leaves. The upper surface of the leaves will have a yellow or white-speckled appearance.

The sunnier the location, the more likely azaleas are to have lace bugs. If sprays are warranted, use insecticidal soaps or a systemic insecticide for control. In many cases, natural predators can keep these pests under control.

Sid Mullis is director of the University of Georgia Extension Service office for Richmond County. Call him at 821-2349, or send e-mail to smullis@uga.edu. The offices that serve Richmond and Columbia counties have a Web page at www.griffin.peachnet.edu/ga/columbia.