How to Stop Azalea Leaves Turning Yellow?

Azalea boasts bell-shaped flowers that can be white, pink, or yellow.

Despite being fairly easy to care for, people still report unprecedented yellowing of azalea leaves. Read on to find out what causes this and how it can be rectified.

Why Do Azalea Leaves Turn Yellow?

Chlorophyll is an important pigment that is present in all photosynthesizing plants. Amongst other things, it’s responsible for giving leaves their green color. Inadequate amounts of chlorophyll can lead to the yellowing of leaves, called chlorosis. 

Chlorosis is one of the first and most obvious signs your azalea is unhappy in its current environmental conditions. Chlorosis can occur for various reasons, be it issues related to watering, nutrient deficiencies, soil pH, sunlight, temperature, or pests

Azalea Leaves Turn Yellow

What Causes Azalea Leaves to Turn Yellow? 

Diagnosing why your azalea leaves are turning yellow is imperative to implement the correct solution as quickly as possible. Below is a list of the most common causes of yellowing azalea leaves and ways to rectify them.

Seasonality

Azalea is a deciduous plant. This means at the end of every fall its leaves will naturally turn yellow and fall off. The azalea then remains dormant to save energy over the winter, before budding in spring.

Azalea leaves often turn yellow in fall
Azalea leaves often turn yellow in fall

Yellow leaves outside this natural cycle suggest your azalea is unwell or unhappy. Here’s a look at some of the major causes. 

Underwatering 

You should water your azalea plant up to twice a week, using around a gallon of water. They have shallow roots, making them vulnerable to drought. As such, underwatering is a very common cause of yellowing azalea leaves.

Symptoms of an underwatered azalea include not only yellow leaves, but overall drooping of the plant, and bone-dry soil too. If left untreated, yellow leaves may become brown, curl inward, and be brittle to the touch. 

In addition to providing a parched azalea with a good drink, I recommend sprinkling some organic matter such as compost on the soil, and carefully mix it in a few layers down. As the azalea roots sit near the surface, there is no need to dig too deeply. 

Overwatering

Overwatering can become an issue when the soil retains water and becomes saturated. This can be a result of planting your azalea in slow-draining soil or using containers that do not have drainage holes. 

Waterlogged azalea can develop a fungal disease called root rot. This is when roots become deprived of oxygen due to an excess of water and die. The dead roots then rot, which can damage healthy roots, potentially killing the plant. 

Symptoms of overwatering include limp leaves with yellow and brown patches that curl in on themselves and eventually drop off the plant. In addition, wilting or drooping is likely to occur.

To fix an overwatered azalea, you should replant it. Compact and heavy soil such as clay should be avoided, and instead, organic-rich compost should be used. It’s also a good idea to mix grit into the soil to aid in draining. 

If you are potting your azalea, make sure you use a container that has basal drainage holes to let any excess water drain away. 

Manganese and Iron Deficiency

Manganese and Iron are essential micronutrients for the growth and development of azaleas, which they absorb from the soil. However, their availability is affected by soil pH, moisture content, organic matter, and aeration. 

Iron deficiency
Iron deficiency

Both Iron and Manganese deficiency manifests itself as yellow leaves with green veins. Additionally, the azalea may show stunted growth and improper or distorted development of leaves, shoots, flowers, and stems. Manganese deficiency is also usually accompanied by brown spots.

You can confirm a suspected case of manganese deficiency by spraying the leaves with magnesium sulfate. This application should cause the yellow leaves to assume their healthy green color. Once diagnosed, you should mix a folic-rich fertilizer into the soil. 

Soil pH 

Azaleas require a slightly acidic soil pH of around 5.5. A pH between the range of 4.5 and 6.0 allows azaleas to absorb essential nutrients, especially iron. Azaleas need iron to make chlorophyll. Soil that is highly alkaline may be detrimental to the health of your azalea. 

Chlorosis is the main symptom that your soil is too alkaline. A high pH level is likely to prevent your azalea from taking up important nutrients. This causes leaves to become yellow and eventually drop off.  

Before attempting to rectify the soil pH, you should determine the level using a pH testing kit. If your soil is too alkaline (above pH 6.0), adjust it to become lower. The easiest way to amend the soil pH mixing mulch, vegetable cuttings, seaweed, and sulfur-rich fertilizer into the soil. 

Excessive Sunlight Exposure 

Although sunlight is crucial for photosynthesis, azaleas are sensitive to too much sun. This species thrives in partial shade, receiving only dappled light for around 4 hours a day. Protection from the very hot, midday sun is recommended to avoid burning. 

Azaleas that have been overexposed to sunlight show symptoms of brown leaves with black patches that are dry and crispy. Additionally, its soil will be bone-dry to touch and they are likely to have reduced growth and flowering. 

To fix this issue, you should relocate your azalea to an area that is out of direct sunlight and provides shade. 

Potted azaleas are easier to move than ones planted in the ground. The latter may benefit from having companion plants that are either tall enough to cast partial shade over the azalea or provide ground cover to protect roots. 

Lace Bugs

Lace bugs are the most common azalea pests. Leaves that have yellow, white, or silvery spots are an indication of a lace bug infestation. They suck sap from patches of the leaf, leading to dry, dead spots.

Lacebugs on Azalea leaves
Lacebugs on Azalea leaves

The easiest way to remove lace bugs from your azalea is to wash them off using a strong jet of water. Applying insecticides to your plant also kills lace bugs. Repeated applications will help control and prevent future infestations. 

Take a look at Why Are My Rose Leaves Turning Yellow? | How to Fix It

FAQ Azalea Leaves Turning Yellow

What Temperature Should My Azalea Be Kept At?

Azaleas thrive in temperatures between 55oF to 61oF.

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.