Brown spots on geranium leaves are caused by different issues, such as fungal or bacterial infections, insect infestations, sunburn, or nutrient deficiencies. If you spot any brown spots on your geranium plant, then this article may just be able to save its precious life.Brown Spots on Geranium Leaves

Continue reading this article as we will tell you about each reason why your plant has brown dots on the leaves, and also the solutions to fix them as well.

What Are the Causes for Brown Spots on Leaves of Geranium?

The causes of having brown spots on leaves of geraniums are fungal or bacterial infections, having an insect infestation. In addition to these, the geranium leaves may also be exposed to too much sun and have sunburn, and lastly having nutritional deficiencies.

– Fungal or Bacterial Infections

Fungal or bacterial infections can cause brown spots on your geranium plants’ leaves. There are many types, but we’ll cover the most common ones.

For instance, the botrytis blight, is commonly known as gray mold, and this fungal infection that can cause leaf brown spots. This fungal infection is common in high humidity and damp conditions.

It can spread quickly from plant to plant, as the brown spots on your plant’s foliage can be caused by a lack of air circulation, especially in humid environments. Remember that this issue may also lead to different fungal or even the development of bacterial infections, which can cause brown spots or discoloration.

A worrying issue for most is bacterial wilt, which is caused by the bacterium Ralstonia solanacearum. This bacterium spreads through the soil and can infect a wide range of plants, including geraniums. It can result in having the leaves to look wilted, turn yellow, and brown, often beginning on one side of the plant and progressing to the entire plant.

Bacterial leaf spot is another common infection that can cause brown spots on plant leaves. This particular disease is easily identifiable by the presence of small, water-soaked lesions on the leaves that turn brown over time. The spots usually have a yellow halo around them, and the leaves tend to wither and die eventually.

Finally, pelargonium rust is caused by the fungal pathogen Puccinia pelargonii-zonalis. The disease is commonly seen in warm and humid conditions and, under these conditions, can quickly infect Pelargonium species and cultivars, to which geraniums belong. It would directly attack the leaves of the plant, causing small, orangey-brown pustules to form under the leaves.

Fungal or bacterial infection or insect infestation may also make it possible for the problem to contaminate and weaken other plants in the area. It’s important to isolate and treat the affected plant properly to avoid spreading the problem.

– Insect Infestations

Spider mites and thrips are two common pests that can cause brown spots on plant leaves. These pests feed on the leaves, causing tiny brown spots that may spread and merge together.Reasons of Brown Spots on Geranium Leaves

They are tiny arachnids that feed on the sap of plants and often attack geraniums. These pests are quite challenging to spot with the naked eye but can easily cause visible damage to leaves, including brown spots. These brown spots often appear first on the undersides of the leaves, causing the leaves to become speckled or mottled as the pests multiply unchecked.

Thrips are small slender insects that feed on the sap of many plants, including geraniums. These unwanted visitors cause damage to geraniums by puncturing the plant cells and sucking out their contents, resulting in brown spots on the leaves. These brown spots may have a silver or bronze sheen and are often accompanied by a distortion or the curling of the leaves.

– Sunburn

While geraniums prefer bright, indirect light, they can tolerate some direct sunlight, especially in the early morning or evening hours. If the plant is exposed to direct and harsh sunlight for extended periods, the leaves may form brown spots due to sunburn.

This usually happens if the plant is suddenly moved from a shady area to a location with direct sunlight or grown in a hot and dry environment. The trauma from the harsh direct sun can cause the leaves to experience damage in the form of sunburned leaves, similar to how human skin reacts to overexposure to harsh sunlight.

These leaves will often develop brown spots that can be circular or irregular in shape. The spots can initially appear on the areas of the leaf that are exposed to direct sunlight, such as the edges or tips. In severe cases, the leaves may turn yellow, wilt, and drop off the plant.

– Nutrient Deficiencies

Nutrient deficiencies can also cause brown leaf spots on geraniums; a lack of magnesium is one of the most common causes. Magnesium is important for plant growth and extremely vital in the photosynthesis process.

This means that if a plant doesn’t have enough magnesium, it can’t produce chlorophyll, which is responsible for the green color of its leaves. The leaves may turn yellow or brown without chlorophyll and develop brown spots, starting to look unhealthy and weakened.

Other nutrient deficiencies or the lack of micro-minerals, such as a lack of calcium, iron, or nitrogen, can also cause brown spots on the leaves of geraniums. Calcium is significant for cell wall development; a deficiency can cause a leaf spot to form on the leaves.

Iron is another necessary element for chlorophyll synthesis, and a deficiency can lead to yellowing and brown spots on the leaves. Nitrogen is influential in the development of proteins, which are very critical to the overall growth of the plant.

A nitrogen deficiency can cause the yellowing of the leaves, which can later develop into brown spots. This is why soil nutrient content is so significant if you wish to grow strong healthy plants.

What Are the Solutions to Treat Geranium Leaves Having Brown Spots

The solution to treat geranium leaves with brown spots is fungicidal spray or bactericides. If the issue has been caused by infection, you can use insecticides, then, and make sure you keep your plant in bright but indirect lighting, and provide proper soil nutrients.

If you notice brown spots on your geraniums, it’s important to identify the cause so you can take appropriate action. You may need to remove affected leaves, treat the plant with fungicides or insecticides, adjust the plant’s lighting conditions, or provide it with appropriate nutrients.

– Use Fungicide or Bactericide

To treat fungal or bacterial infections, you need to remove affected leaves immediately to prevent the spread of the disease. Use a pair of clean, sterilized, sharp scissors or pruning shears to cut off the affected leaves, making sure to dispose of them properly.

Next, treat the plant with a fungicide or bactericide as directed on the label. There are various products available for treating fungal and bacterial infections, so make sure you choose the appropriate one for the type of infection you’re dealing with.

Some common fungicides include copper-based sprays, neem oil, or potassium bicarbonate. You can use a copper-based spray or a bactericide containing streptomycin sulfate for bacterial infections.

When applying the fungicide or bactericide, follow the instructions placed on the label carefully. Some products or chemicals may need to be diluted before use, while others may need to be applied directly to the leaves. Make sure you are targeting all the parts of the plant, even the undersides of the leaves.Solutions to Brown Spots on Geranium Leaves

It’s also important to keep the plant dry to stop the spread of fungal and bacterial infections. Avoid having any water droplets come on the leaves when you water the plant, and make sure the soil is one that is well-drains as it will prevent water from pooling around the roots.

– Use Insecticides

To treat spider mites or thrips, you can also opt to spray the plant with a solution of neem oil or insecticidal soap. You should redo the treatment every few days just as the infestation is under control. It’s also significant to keep the plant well-watered and to remove any severely affected leaves to prevent the infestation from spreading.

In some cases, severe infestations may require more aggressive treatments, such as synthetic insecticides, but these should be used with distinct caution and only as a last resort. This is all due to the key cause that they may be harmful to you and your household, especially when inhaled or ingested accidentally.

– Keep Your Geranium in Bright, Indirect Light

To prevent sunburn, it’s essential to provide the geranium plant with the right amount of light. Geraniums prefer bright but indirect sunlight, so it’s best that you would place them near a window that receives bright light but is shaded by a sheer curtain or a tree outside.

If the plant has been indoors for a long time, gradually expose it to more sunlight over several weeks to help it acclimate to the increased light. If the leaves are severely damaged, you may need to trim them to promote new growth. Use clean, sterilized, sharp pruning shears to cut the damaged leaves near the base of the stem.

– Provide Adequate Soil Nutrition

Geraniums require a balanced supply of nutrients for optimal growth and health. A lack of nutrients, especially magnesium, can cause brown spots on the leaves. To address this issue, you can test the soil and select the right fertilizer to add vital nutrients to the soil.Details of Brown Spots on Geranium Leaves

It’s important to test the soil to determine if there are any nutrient deficiencies. You can try using a soil test kit or send a portion of your soil to a lab for analysis. Next, choose a fertilizer that is specifically formulated for geraniums and contains all the necessary nutrients, including magnesium.

Fertilizers come in different forms, including liquid, granular, and slow-release. Follow the guidance given on the label of the product carefully to avoid over-fertilizing. Then, apply fertilizer as instructed on the label to the plant when it’s actively growing, and make sure the soil is humid before applying. Avoid having fertilizer come on the leaves, as this can cause burning.

Use organic methods to provide your geranium plant with essential nutrients where possible. For example, you can apply compost or organic mulch to the soil to slowly release nutrients over time.


If you see a leaf spot on your geraniums, you won’t have to worry anymore since you know the possible causes and solutions. Here’s a quick recap on how to treat geranium diseases, especially the brown spots on their leaves:

  • Use fungicides or bactericides to treat fungal and bacterial infections.
  • Apply organic insecticides, where possible, to eliminate insect infestations.
  • Keep your geraniums in areas that receive bright but indirect light.
  • Fertilize your plants regularly, preferably with organic fertilizers such as compost.

With that out of the way, now you can expect to grow bushy, flowering, and exceptionally healthy geraniums.

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