Why are my azaleas yellow?

Randy Drinkard Extension agent

December 20, 2013

As we head toward the new year, gardeners try to make their landscape look its best. That is when they contact University of Georgia Extension. We provide unbiased, research-based information to help Georgia homeowners grow healthy gardens and landscapes.

One of the questions we have received recently is, “Why are my azaleas yellow?” I have seen this problem before, but it seems more severe this year in the Troup County area. Usually we see a few older leaves yellowing with the younger leaves remaining green. In a number of cases now many leaves are turning yellow and orange. Why is this so bad this year?

Keep in mind that losing some leaves is a normal process. The older leaves die and younger ones replace them. I would only be concerned if most of the leaves are yellow.

The traditional reply I have given in the past is that the plants have run out of fertilizer, particularly nitrogen. Nitrogen-deficient azaleas will shed older leaves. This is certainly a possible cause. Azaleas may have missed being fertilized in July or August, or they were unable to absorb fertilizer due to rains leaching it out of the root zone too quickly.

I would not worry about these plants. They should grow and bloom normally in the spring. Fertilize them after the danger of frost is past – about April 1. Do not fertilize them now. This may cause the plant to initiate new growth. This new growth is cold-tender and may be injured or burned back by our winter weather.

Our unusual weather may be causing a problem with azaleas. Azaleas are a Southern favorite, but they are somewhat temperamental. Their fine fibrous roots like well-drained but moist soils. This year’s unusually wet weather may have damaged the roots. This is especially a problem in areas not suited for azaleas. Azaleas do not like overly wet, or very dry soils, or full sun locations.

There is not much we can do about this now. Fertilizing at this time will not fix this problem. Proper planting and maintenance will help prevent this problem in the future.

Plant azaleas in well-drained soils in partially shaded locations. The shade provided by planting them next to a building is not always enough shade. If they must be planted in the sun, they prefer the morning sun. Plant azaleas in slightly raised beds, if possible. Plant them no deeper than they originally grew.

The roots may be pot-bound when you buy them. This is when the roots are tightly matted together. Pot-bound roots form a tough ball that the roots may never grow out of. Cut the root ball or break the roots down four sides of the root ball if the plant is pot-bound. Spread the roots out as you add soil to the planting hole.

Plant azaleas in beds, not individual holes dug in the ground. Till the area well. Put a three-inch mulch over the entire bed after planting. Water the soil well to settle the roots. Plant in fall and winter for best results.

Azaleas and other shrubs must be watered after planting for best results. This is a very important step. In addition, proper watering during the first year may determine whether the plants survive. Water the soil to keep it evenly moist but not overly wet for the first six months. After that, water when the soil dries out, wetting the soil to a depth of 12 inches.

I usually recommend watering 3/4 to 1 inch every week to 10 days. After azalea plants are established, do not water every day or even every other day! Too-frequent watering can kill the plant’s roots.

Two other leaf problems with azaleas are iron deficiency and lace bugs. An iron deficient azalea will have yellow or white younger leaves. The leaves will be yellow with green veins. Use a soil applied iron fertilizer at the labeled rate. If the iron deficiency returns quickly or repeatedly, the azalea may have root injury or the soil pH may be too high.

Lace bugs make the leaves look speckled or silvery. The underside of the leaves will be brown speckled. Wait until March and treat them with a recommended insecticide. Read and follow all label directions.

Enter the new year with healthy azaleas. Azaleas may look sad now but will return to health with proper care.

Randy Drinkard is a technical writer for The UGA Center for Urban Agriculture and ANR Agent for Troup Cooperative Extension. The Troup County Extension office is located at 114 Church St. in LaGrange and may be reached at 706-883-1675, Monday through Friday, 8 a.m. to 5 p.m.