I have a row of evergreen azaleas growing near my concrete driveway. The first couple seasons they looked very good, but now they look worse every year. The foliage is turning more and more yellow. Can these plants be saved?
The symptoms you describe appear to be iron chlorosis. This is a very common problem in acid-loving plants like azaleas. It is caused by a deficiency of iron in plant tissues. Although soil is seldom deficient in iron, the iron is often in a form that the plant cannot take up through its roots. This is especially true when the soil’s pH is 7 or higher. Plants located near concrete driveways, paths or walls are especially susceptible to chlorosis.
First, get your soil pH tested. There are several reliable products on the market that can correct the problem. Make sure the product label is followed correctly in accordance with the results of your soil test. Depending on the results, you can increase the soil acidity by adding the correct proportions of iron sulfate, ammonium sulfate, or sulfur. You can also mulch the soil with leaf mold or pine needles in combination with the application of an appropriate fertilizer for acid-loving plants. With some immediate treatment and moderate long-term maintenance, your azaleas should be looking as good as they did when you first planted them.