The Agapanthus plant has beautiful evergreen leaves, however, there are some instances when its leaves can turn yellow or even brown. If this is the first time you see the leaves of your Agapanthus turning yellow, then don’t worry in most cases it is just a natural process. On the other hand, if only some of your Agapanthus plants are getting yellow leaves then there might be some underlying issues that you should address before the entire plant dies off.
There are several reasons why your agapanthus plants may be turning yellow. It could be due to a pest infestation or an iron deficiency caused by alkaline soil. Another possibility is a fungal disease that is affecting the leaves. Overwatering or excessive sun exposure can also lead to yellowing.
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There are literally hundreds of different varieties of Agapanthus plants, most of them are hardy between zones 8-10. If you are growing them outside their preferred hardiness zone then you will see that the leaves of the Agapanthus will turn yellow from time to time. Agapanthus plants are prone to several diseases, but the good news is that most of them are easily noticeable like gray mold or powdery mildew.
If the plant has some disease then it is not uncommon for some of its leaves to turn yellow or brown. If you do not like how these yellow leaves look, you can simply cut the entire Agapanthus plant to the ground and it will come back in the spring. If you want more information about Agapanthus then check out my recent article Agapanthus Africanus ( Lily Of The Nile, African Lily ).
Agapanthus Leaves Turning Yellow
When Agapanthus leaves start turning yellow, it can be an indication of various underlying issues. One common cause is overwatering, as excessive moisture can lead to root rot and nutrient deficiencies. To address this, ensure that the plant is receiving appropriate drainage and water it only when the top inch of soil is dry. Another potential cause is a nutrient imbalance, particularly a deficiency in iron or magnesium. Applying a balanced fertilizer or supplementing with appropriate nutrients can help rectify this issue.
Additionally, yellowing leaves may result from pests, such as aphids or spider mites, feeding on the foliage. Use insecticidal soap or neem oil to combat these pests. Lastly, excessive sunlight or heat can cause leaf scorching and yellowing. Provide some shade or relocate the plant to a cooler spot if necessary.
Due To Cold
The most common reason why Agapanthus leaves turn yellow is caused by cold, even a slight frost can change the color of the leaves. Agapanthus plants do not like cold, and oftentimes in colder regions their leaves will turn yellow, then brown, and will eventually drop off. If you are growing Agapanthus outside its preferred hardiness zone then this is a normal process, most Agapanthus plants will be able to resist some frost damage and they will come back in the spring.
If autumn is right around the corner and the nights are getting colder you will notice that the bottom leaves are starting to turn yellow, and in a few weeks most of the leaves are yellow. At this point, you can simply cut the plant back to the ground, as it will come back once the temperatures are high enough. In case you want to add some good companion plants to your Agapanthus then check out my recent article Agapanthus Companion Plants ( Top 25 ).
Due To Too Much Water
Agapanthus plants are native to South Africa, their native soil is relatively poor and they are used to short periods of drought. Agapanthus plants will really struggle if they are overwatered or if the soil is waterlogged. Usually, you will see that the leaves of the Agapanthus will turn yellow in a matter of days if it gets too much water from either rain, overwatering, or if its roots are constantly in water.
To fix this issue you only should water your Agapanthus plants once the topsoil starts to become dry. If you have clay soil in your garden then the most likely reason the Agapanthus leaves turn yellow is that the roots are in the water, as clay soil is not draining well. In this case, you should really consider planting your Agapanthus in a pot, this way you can use a well-draining soil mix, for more information check out my recent article Pots For Agapanthus ( Top 8 ).
Due To Iron Chlorosis
Iron Chlorosis simply means that the plant doesn’t get enough iron, usually, the soil is poor in iron or the plant can not use the iron in the soil due to diseases or other factors. In the case of Agapanthus plants if they do not get enough iron you will notice their leaves turning yellow in a week or two. Generally speaking, iron deficiency is usually caused by overwatering, as too much water will simply wash away the iron.
On the other hand, the pH of the soil also affects how Agapanthus plants can absorb iron. Get a simple soil testing kit, and see what the pH of the soil is, if it is above pH 7-8 then try to lower its pH to 6.5. You can use sulfur to reduce the pH of the soil, just keep in mind that this is a temporary solution and you will need to test your soil from time to time.
If you do not want to mess with the pH of your soil then use a foliar fertilizer that contains iron, and spray the leaves of the Agapanthus. Plants can absorb nutrients with their leaves as well so a foliar fertilizer will fix the leaves turning yellow if it can’t absorb iron with its roots.
Due To Too Much Sun
Agapanthus plants love full sun, but in some cases, they will start to suffer and their leaves will turn yellow and brown eventually. If your local climate is relatively dry and the humidity is low, then your Agapanthus plant will struggle. In this case, either provide the Agapanthus plant some shade from the mid-day sun or replant it in a partial shade location. If you have just planted the Agapanthus then let it be for a couple of weeks and it should bounce back.
Watering Agapanthus In The Middle Of The Day Can Make Its Leaves Turn Yellow Or Brown
If your watering schedule is in the middle of the day when the sun is the hottest then you might do more harm than good if you are watering your Agapanthus from above. Water droplets on the Agapanthus leaves are like miniature magnifying glasses that channel the sun’s rays into a single spot. Usually, you will start seeing a couple of small holes in the leaves and then the leaves will slowly turn yellow. The simple fix for this is to water your Agapanthus form below.
Transplant Shock
Transplant shock occurs when you transplant your plant from one place to another or simply bring it home and plant it into the soil. Every plant can suffer from transplant shock and this is normal, it will take a couple of days until the plant bounces back. In some cases, transplant shock can simply kill off the Agapanthus plant, its leaves will turn yellow, then simply fall off. To limit the transplant shock make sure to give the Agapanthus plant some partial shade for the first couple of weeks.
Simply get an umbrella and make some shade for the Agapanthus in the afternoon when the sun is the brightest.
Pests
Agapanthus plants are prone to having a couple of pests like Mealybugs, Thrips, Gnats, and Spider Mites. If you have any of these in your garden then odds are that they will go for the Agapanthus plant as well. Young Agapanthus plants or ones that have transplant shock will suffer the most from these pests, as they do damage their leaves. The good news is that once the plant is mature and established it will be able to fend off most of these pests.
Diseases
Agapanthus plants are prone to the following diseases Leaf Spot, Powdery Mildew, Gray Mold, Anthracnose, Root Rot, and Bulb Rot. Established plants will suffer less from these diseases, but young plants will get yellow leaves sooner or later if they are affected by any of these diseases. Oftentimes even when the plant fights off these diseases, some of its leaves may turn yellow and drop. The good news is that new shoots will appear in a matter of days and these will usually be healthy ones.
Key Takeaways
- The most common reasons why Agapanthus leaves turn yellow are due to cold and overwatering. Agapanthus plants are not that cold hardy and even a slight frost can turn its leaves yellow. Agapanthus plants really suffer when they get too much water, their leaves will start to turn yellow or even brown. In addition to this iron chlorosis, or even transplant shock can turn the leaves of the Agapanthus yellow.
- Overwatering can also cause the leaves of the Agapanthus to turn yellow, so make sure not to water it too much and that the soil is well-draining.
- If you suspect that the leaves of your Agapanthus plant are turning yellow due to lack of iron, then before amending the soil with sulfur to lower the PH, start with a simple foliar fertilizer that contains iron, and see how the plant responds.
