Yellow Leaves on Gardenia – How to Fix

If you have seen some yellow leaves on gardenia, do not worry, here we will inform you about the possible causes and how to fix the problem on gardenias.

Chlorosis is a problem in which the amount of chlorophyll in the leaves is reduced. Chlorophyll is a pigment present in the young leaves and stems of plants that gives them their characteristic green color. When the content of this pigment decreases, leaves appear yellow, brown, or even white in some cases.

While there can be a variety of causes for why gardenias show yellow leaves, the most common are overwatering, mineral deficiencies, and insufficient sunlight. Below are the most common causes of yellow leaves on gardenia and some remedies to stop this yellowing.

Yellow Leaves on Gardenia

The causes of yellow leaves on gardenia are caused by a number of factors. The most common ones include:

  • Sunburn.
  • Insects.
  • Drought.
  • Improper watering.
  • Nutrient deficiency.
  • Bacterial or fungal disease.

Throughout this article, you will learn all about yellow leaves on gardenia. We will also explain what is the best fertilizer for gardenias with yellow leaves.

Yellow Leaves on Gardenia Due to Magnesium Deficiency

Lack of magnesium in gardenias may be one of the causes of yellow leaves. The yellowing will be seen on the outside of the leaf, and the center will be green (photo below).

To fix yellow leaves on gardenia due to magnesium deficiency, you can add a fertilizer that is rich in magnesium or use Epsom salts.

yellow leaves on gardenia magnesium deficiency
Gardenia yellow leaves due to magnesium deficiency.

Gardenia Yellow Leaves Due to Iron Deficiency

Iron deficiency can also cause yellow leaves on gardenia. The leaves are very similar to magnesium deficiency.

The solution to yellow leaves in gardenias due to lack of iron is to add iron powder (for plants) or some fertilizer that has plenty of iron. Apply once every two to four weeks.

Learn more about What is ferrous sulfate iron used for?

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Yellow Leaves from Excess Fertilizer

Also, the excess of fertilizers is bad for the gardenias, one must have a balance with the nutrients that it provides to the plant. Too much fertilizer can burn the root of the plant and where it will be almost impossible to save the gardenia plant. We recommend this fertilizer for gardenias.

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gardenia excess fertilizer
Fertilizer for Gardenias with Yellow Leaves. A 20-20-20 or 15-15-15 fertilizer will be very good for a gardenia with yellow leaves due to lack of fertilizer.

Gardenia Pests

Pests such as mealybugs and aphids are also to blame for yellow leaves on gardenia. These pests usually suck the sap from the plants and leave a sticky secretion that causes a fungus to grow which blocks sunlight, so the plant does not photosynthesize properly.

Some of the most common gardenia pests are aphids, spider mites, mealybugs, and whiteflies. Aphids are small insects that feed on the sap of plants and cause them to wither. Spider mites are tiny creatures that live on the underside of leaves and suck out their juices. Mealybugs are also insects, but they secrete a sugary substance called honeydew which turns into the mold and attracts more pests like ants. Whiteflies lay eggs in new growths which then hatch into larvae which cause stunted growths, yellowing leaves, wilting, and dying plants in some cases.

The solution to combat the pests in gardenias with yellow leaves is to use neem oil or an organic pesticide to eliminate these pests as soon as possible from the plant.

gardenia pests
Insects attacking a Gardenia leaf.

Excess Watering

Too much water can cause yellow leaves on gardenia, so it is important to control the amount of water. If the plant is in the ground directly, stop watering for a few days, but if it is in a pot, it is best to change some soil so that the roots do not rot.

Gardenia is an acidophilus plant, therefore it requires an acid substrate. A pH of around 5 may be sufficient for the gardenia to absorb nutrients normally, otherwise, its leaves will turn from green to yellow. Learn more about how to measure soil pH.

gardenia yellow leaves
Gardenia Yellow Leaves.

Fertilizer for Gardenias with Yellow Leaves

Fertilizer for gardenias with yellow leaves. Fertilize your gardenias every 15 days in spring and summer with a little liquid fertilizer dissolved in the irrigation water. If possible, use special fertilizer for acidophilus plants, that is, plants such as hydrangeas, azaleas, heather, etc. that need acid soil.

Gardenia requires fertilizers rich in phosphorus and potassium and those that give acidity to the soil. The most suitable fertilizer for gardenias with yellow leaves is 20-20-20 or 15-15-15. Granular fertilizers should be applied once a month or, if they are liquid fertilizers, every 15 to 20 days.

When we refer to 20-20-20 (or any number) we mean Nitrogen, Potassium, and Phosphorus (NPK). Learn more about different types of fertilizer.  

Gardenias need strongly acid soil, so from time to time, you should use a fertilizer rich in iron (e.g. iron chelates), especially if the leaves turn yellow, which is a sign that they are lacking this nutrient.

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Yellow Leaves on Gardenia – Final Conclusions

As you may have observed there can be several causes of yellow leaves on gardenias, our recommendation is that you never overwater your plants in general and control the fertilizers so that you do not over-fertilize. Hopefully, this note about yellow leaves on gardenia will be of great help, and you will be able to solve the problems with your plant.

About Henry Morgan

We are the Morgan family, Henry, and Julia, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for TheGardenStyle.com as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website.