Why Are My Agapanthus Leaves Turning Yellow?

Agapanthus, also known as the African lily, is a popular ornamental plant known for its striking blue, white, or purple flowers that bloom during summer. 

Agapanthus Leaves Turning Yellow

While this plant is relatively easy to care for, it’s not perfect, and it has its own problems, such as yellowing of leaves. Agapanthus leaves turning yellow can be a sign of various issues, ranging from simple cultural problems to more serious diseases or pests. In order to effectively address this problem, it’s important to identify the underlying cause of the yellowing leaves

So, why are my agapanthus leaves turning yellow? The main causes of leaves turning yellow are; overwatering, excess sunlight, diseases, pests, and lack of iron. 

This article will explore the common reasons why agapanthus leaves turn yellow and provide some tips for maintaining healthy plants. 

What causes agapanthus leaves to turn yellow?

When a leaf turns yellow, most people assume it’s not a big deal. It might not be a big deal at the moment, however, with time, it will be big. The best time to fix the yellowing of leaves is when you notice it on them. 

Agapanthus Leaves Turning Yellow

You can save your plant from dying if you do it in its early stages. So, what causes the agapanthus leaves to turn yellow? 

Here are the reasons; 


Overwatering is a common problem that affects most garden plants. It happens when you give the plant more water than it requires. Since the plant can’t absorb all the water, the rest remains in the soil, creating waterlogged soil. 

The soil with excess prevents air circulation to the roots, which can result in root damage. Besides that, the excess creates a fungal disease that causes root rot. As the roots rot, they stop feeding the rest of the plant, causing agapanthus leaves to turn yellow. 

Signs of overwatering include; 

  • The bottom leaves turn yellow
  • Soil is always wet
  • Plants start to wilt
  • Leaves are swollen

One way to determine if overwatering is the cause of yellowing leaves is to check the soil moisture level. If the soil is consistently wet or waterlogged, overwatering is likely the culprit. You can purchase a moisture meter to check the moisture level in the soil. 

There are two ways you can fix this problem. First, if the roots haven’t been affected, allow the soil to dry for a week before watering again. That will allow the plant to use all the water in the soil. Secondly, if the roots are affected, you must repot the plant with fresh soil. Cut off all the affected roots with a sharp garden knife. 

Also, ensure that you are using well-draining soil so that the excess water can drain away from the roots. The pot should have draining holes at the bottom to avoid accumulating water at the bottom of the container. 

Excess sunlight 

Agapanthus is a plant that likes to grow in full sun to thrive, however, at times, the sun becomes excess for the plant. The plant requires about 6 hours of sunlight and some shade to grow. So, you can place the plant in an area with partial sun and shade.

When a plant is exposed to too much direct sunlight, it can cause a condition known as sunburn or scorching. This can damage the leaves and prevent the plant from photosynthesizing properly, leading to the yellowing of leaves at the edges and wilting. 

Agapanthus Leaves Turning Yellow

On the other hand, sunlight can cause the soil to dry by evaporating all the water. That can result in underwatering, and the plant cannot absorb enough water and nutrients to stay healthy and green. Thus, it causes agapanthus leaves turning yellow. 

To prevent sunburn, plant it in an area that receives afternoon shade. Also, place mulch or grass clippings around the plant and then mist them with some water to prevent the sun from dehydrating the plant. 


Unfortunately, it is easy for agapanthus to be attacked by diseases. For instance, most fungus-based diseases, such as root rot, Fusarium wilt, rust, and leaf spot, can attack the plant, causing the leaves to turn yellow. 

Fungal diseases are caused by overwatering, poor air circulation, and a damp or humid environment. Viral diseases such as agapanthus mosaic virus are caused by insets or through infected plant material. 

Other than agapanthus leaves turning yellow, these diseases can cause brown spots on leaves, distorted leaves, drooping leaves, and stunted growth. 

To prevent the spread of diseases, prune all the affected parts of the plant, including the roots. Remove the plant from the soil to check for agapanthus root rot. Healthy roots are white and firm, while rotten roots are brown, soft, or mushy. After pruning, repot the plant in fresh soil and a sterilized container. 

Apply fungicide every 7 to 10 days. Also, keep the area around the plant clean and avoid overwatering. 

Agapanthus Leaves Turning Yellow


Pests such as mealybugs and red spider mites love infesting agapanthus. They tend to suck the sap in the leaves, causing damage to the plant tissues. Once the tissues are damaged, they turn yellow, wilt, and die. 

You can keep away pests by spraying an insecticide such as neem oil. You can mix it with water and spray it when watering the plant. Keep applying it until all the pests are gone. 

How does a lack of iron cause agapanthus leaves turning yellow? 

Iron is an important micronutrient that plays a critical role in producing chlorophyll, the green pigment necessary for photosynthesis. Without enough iron, the plant cannot produce enough chlorophyll, resulting in yellowing or even whitening of the leaves.

The first sign of lack of iron in the agapanthus plant is when the new growth turns yellow as the veins remain green. When this happens, the problem is either the soil lacks iron or the plant can’t absorb iron from the soil. 

First, test the soil to ensure it has sufficient nutrients. You can purchase a soil test kit to test the soil at home. The kit has instructions on using and what to expect from the soil when the results are shown. 

If the soil shows a pH higher than 7, lower it to 6.5. A higher soil pH affects the agapanthus plant roots, limiting them from absorbing iron in the soil. Once you reduce the pH, the roots will start absorbing the nutrients. Use sulfur to lower the pH of the soil. 

If the soil lacks iron, you can add fertilizer to the soil that contains iron. You can do this by adding an iron supplement to the soil or by applying a foliar spray containing iron.

Agapanthus Leaves Turning Yellow


In conclusion, yellowing of leaves in agapanthus plants can be caused by various factors. Identifying the specific cause of yellowing is important to take the appropriate action to remedy the problem.

Practicing good plant care, such as ensuring proper watering and providing the right amount of sunlight, can prevent agapanthus plant leaves from turning yellow. Also, monitor your plant’s health and take prompt action when a problem arises. 

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