5 Causes of Agapanthus Plants Turning Yellow [360 Degree Solution]

Agapanthus is an eye-catching beauty with purple flowers and strap-like leaves. But like all other plants, they too are susceptible to some environmental problems. But luckily they show some symptoms cluing us in to what problem they are facing. Yellowing of leaves is one of them.

When the agapanthus leaves are turning yellow as a grower you need to take immediate steps before the plant starts dying. Taking the wrong action may end up killing your plant.

So, why are the agapanthus leaves turning yellow?

The 5 most common reasons are overwatering, Iron chlorosis, Sunburn, Pest attack, and Diseases. Sometimes multiple reasons combinedly can produce yellow leaves on agapanthus plants.

But you don’t have to worry about that at all. Because this article is here to help you get your answers with easy solutions to treat the yellow leaves of your agapanthus.

Why Are The Agapanthus Plants Turning Yellow?

1. Overwatering

Overwatering is one of the major reasons why the agapanthus leaves are turning yellow. If you continue to overwater the agapanthus, their lower leaves will turn yellow at first, and soon they’ll die. Too much water also makes the leaves soggy and invites other fungal diseases.

Control Measure

Agapanthus doesn’t like their roots to be wet. So, water only when the top three inches of the soil is dry. During the rainy season, you don’t need to water if there is enough rainfall. Get a moisture meter to get a correct idea of when to water your agapanthus (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden).

While watering, do not water wetting the leaves. Rather, water on the base of the plant to avoid any fungal attack.

2. Lack of Iron

When agapanthus leaves lack iron their leaves start turning yellow. Sometimes there may be plenty of iron available in the soil. But the agapanthus won’t be able to uptake them because of the high soil pH.

Continuous iron chlorosis leads to unhealthy agapanthus with drooping leaves. The leaves turn yellow with green veins.

Control Measure

Pick the best fertilizer for your agapanthus that contains iron (our pick: Miracle-Gro Water Soluble All Purpose Plant Food). Apply the fertilizer by following the instructions of the manufacturer.

Check your soil pH with a pH meter. If the pH is higher than 7, amend the soil with some sulfur or other acidic fertilizers or organic mulches.

3. Sunburn

Agapanthus grow the best under full sunlight but sometimes too much heat from the sun can cause sunburn to them. This can make the tips of the agapanthus turn yellow.
They need 5-6 hours of sunlight every day but during very dry spells the heat from the sun can burn their leaves.

Control Measure

Protect your agapanthus by giving some afternoon shade during very hot and dry spells. Also, spread a layer of mulch around the plant. This mulch will help keep the moisture, insulate the heat and keep the soil cool.

4. Pest Attack on Agapanthus

Spider mites and mealybugs attack agapanthus a lot. Both these pests suck the juice out of the leaves and make small holes in them. As a result of their feeding, the leaves turn yellow. When their infestation spreads the whole leaf completely turns yellow and starts to wilt.

Control Measure

Control these pests as soon as you see them because their feeding will weaken your agapanthus a lot. Get the best and safest insecticide for your agapanthus that is very effective in killing pests (our pick: Monterey organic Garden Insect Spray). Remember to spray the insecticide thoroughly on both sides of the agapanthus.

You can also get rid of these pests with homemade insecticide sprays. Check out some quick and easy recipes

#Recipe 1:- Horticultural Oil Recipe


  • 2 tablespoons of liquid dish soap
  • 500 ml of any cooking oil


  • Mix these ingredients very well.
  • And store the mixture in a bottle.
  • Take one tablespoon of this mixture with 250 ml of water.
  • Pour it into the sprayer.
  • Spray this every week on both sides of your agapanthus leaves.

#Recipe 2:- Neem Oil Recipe


  • 1 tablespoon of neem oil
  • 2 liters of water


  • Mix the ingredients and spray in the plants every week.
  • Apply this on your agapanthus leaves on a regular basis as a preventive measure.

Note: Before using them on the whole agapanthus plant, try it on a small leaf to see how it reacts. If the leaves distort or burn then mix some water to dilute the solutions.

Beware that agapanthus leaves are dangerously poisonous. So be very cautious while handling the plant. Wear gloves while working with it. Because It can cause skin irritation. It can also cause swelling on the throat and mouth if ingested.

5. Fungal Diseases of Agapanthus

When your agapanthus is in damp soils and shaded conditions many kinds of fungal diseases can attack them. The diseases like root rot, leaf spot, and anthracnose turn the agapanthus leaves yellow.

Control Measure

First, remove all the infected yellow leaves from the plant and discard them very carefully. Do not let them get in contact with other plant parts.

Then apply a good fungicide to your agapanthus that is very powerful against fungal diseases (Our Pick: Bonide Copper Fungicide). Apply every 10 or 15 days intervals until the disease is gone.

Make sure your plant gets plenty of sunshine and airflow around them. Do not let them stay in damp and humid conditions.

In the case of root rot, dig the plant up and prune the infected parts of the root that look black and soggy. Treat the root with a disinfectant and replant the agapanthus in the soil.

For your potted agapanthus, If you suspect fungal growth then replant the whole plant in a new and freshly prepared soil mixture.

Make sure the pot is big enough to let the roots grow. Keep enough holes in the pot so that excess water can drain through the holes. Remember, overwatering bring fungal diseases. So water only when the soil is dry.

Try these quick and amazing homemade fungicides recipes-

# Recipe 1- Baking Soda Spray Recipe


  • Baking Soda 1 tablespoon
  • Few drops of liquid dish soap
  • 3 liter of water


Mix the ingredients well and spray thoroughly on both sides of the diseased agapanthus leaves.

#Recipe 2- Vinegar Spray Recipe


  • 1 tablespoon of apple cider vinegar
  • 2 liters of water
  • Few drops of liquid soap


Mix the ingredients very well and spray on the infected agapanthus leaves twice a week.

# Recipe 3- Epsom Salt Spray Recipe


  • 2 tablespoons of Epsom salt
  • 2 liter of water


  • Mix them very well.
  • Spray this solution on your agapanthus every week until the problem is solved.


Agapanthus is one of the popular picks for gardeners because they are very easy to grow. But still, like all other plants growers have to face some common problems such as the yellowing of leaves on the agapanthus.

If you spend some time taking care of your plant by spraying pesticide and fungicide regularly, watering the right amount, and keeping the plant safe from the scorching sun then your plant will soon revive back to normal.

But if your agapanthus leaves are turning yellow in winter then you don’t have to worry about that very much. Because it’s very common for them to turn yellow during winter. It will come back to its mossy green form in the spring season.

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