5 Causes of Petunia Leaves Turning Brown [Control Measure]

Petunias are gorgeous garden blooms native to South America. And It can defend itself from different problems.

But it’s hard to deny that sometimes the Petunias can suffer from some issues and Browning leaves of Petunias is one of them.

Don’t worry! This problem can be fixed easily. But before diving into the deep, we have to know, what are the causes of the brown leaves of Petunias?

Improper watering, fungal infestation, pest attack, damaged roots, and improper fertilizing are the main culprits behind the problem.

In this article, I will discuss the reasons in detail with the practical solutions.

Why are the Petunia Leaves Turning Brown?

1. Improper Watering

You know that insufficient watering causes your plant to wilt and dried up. Leaves can also be brown due to this reason. 

But have you ever imagined that too much watering can also be harmful? Well, this is a common mistake that will gradually turn your petunia leaves brown. 

If your petunias look wilted even after having enough water in the soil, this might be because of excessive watering. Overwatering can cause your petunias bottom leaves turning brown.

So if you notice some brown leaves with wilted plants, then you better check your watering schedule.

Control Measure

Water deficiency can easily be resolved by adding some water to your petunias. Keep checking that the soil near the base doesn’t dry up easily.

Now let’s come to the overwatering issue. Unfortunately, it’s a bit tricky to handle when your plants have already wilted because of this. All you need to establish a proper watering schedule.

Normally watering once a week is appropriate for petunias in proper drainage conditions. You may need to water some extra on hot summer days. Just according to you soils need.

2. Fungal Infestation

Here comes the most devastating and bothering issue; fungal attack. This starts from brown spots on petunia leaves.

Multiple brown spots underside of the leaves are a symptom of rust disease caused by fungus. A wet environment promotes such conditions. You may also observe some sunken lesions on leaves caused by anthracnose. Another type of fungal spot can be marked as central brown spots with yellow edges. 

If you can trace any of these symptoms, you should take proper steps as soon as possible.

Control Measure

Neem oil-based fungicides are a good and safe pick for the fungal attack of petunia. A 2% concentration is mostly advised. (Our Pick: Organic Neem Bliss 100% Pure Cold Pressed Neem Seed Oil)

Also, copper fungicide is effective. Use this formulation on the upper and lower side of your plant leaves according to the instructions. (Our Pick: Bonide Copper Fungicide Rtu Natural ) You may need to follow this every 7 to 14 days to see improvement.

Caution- Don’t forget to use gloves while handling these fungicides.

Home Remedies

#Recipe 1: Daisy Concoction 


  • Painted daisy.
  • 30 ml of Alcohol.
  • 15 liters of water.


  • Dry flower heads and grind them in alcohol. Or you can simply soak them in alcohol overnight.
  • Mix this with water and strain this solution with a cheesecloth.
  • Pour this in a spray bottle and apply it to your plant.

#Recipe 2: Baking Soda Mixture


  • 2 teaspoons of baking soda.
  •  2 liters of water.


  • Mix baking soda in water.
  •  Apply this to your plant with the help of a sprayer.

Preventive Measure

First of all, place your petunias in an open place where there is enough sunlight and air circulation. In landscape conditions, avoid crowding of plants.

Try to maintain proper moisture. Fungal spores can transmit via soils. So, don’t let them grow in your petunia soil.

Another key thing to remember is to avoid overhead watering as much as possible. Water only at the base as per need.

Last but not the least, keep garden debris away from your plants. These can be a habitat for fungal pathogens.

3. Pest Attack

I believe that nothing has bothered you more than pests in your gardening journey. Thrips, scales, mealybugs, spider mites, and aphids are the most devastating. Infestation of these insects gradually damages your petunia leaves and turns them brown.

Thrips attack on the shooting stage causing petunia buds turning brown.  Spider mites and aphids suck the juice up from your leaves. This causes yellow and brown leaves of the plant.

Control Measure

Pest attacks can also be associated with fungal infestation. So, at first look for insects in your plants.

If you can detect any, simply go for horticultural oils or soaps. These are effective for mild infestation. (Our Pick: Natria Insecticidal Soap)

Choose an effective insecticide for severe conditions. (Our pick: Monterey Garden Insect Spray)

Home Remedy

You may not need any chemical formulation in preliminary conditions. So here is a homemade solution for you.


  • 5 tablespoons of liquid soap
  • 5 tablespoons of vegetable oil.
  • 8 liters of water.


  •  Mix all the ingredients together.
  • Apply this to your petunia with the help of a spray bottle.

Caution – Avoid soaps that have high bleach content.

4. Damaged Roots

Root damage can be marked as a severe problem in plants as rotten roots can’t be restored. Injured or diseased roots can hamper water uptake from soil. This is another culprit for brown leaves in your petunia. Petunia turning brown at the base is the first sign of root damage.

In the case of pot planting your petunias may suffer from root bound. Plant roots accumulate densely in a smaller pot which hinders water uptake. Even such gathering of roots also promotes root rot disease. 

The associated symptoms simply include petunia leaves turning yellow and brown.

Control Measure

To control further damage keep checking your plant roots. You may need to trim them according to damage.

Rotten rot is a sign of a fungal attack. So, find some remedy from the ‘fungal infestation’ segment in this case. However, most of the time rotten roots need to be cut off.

Repotting may help you to develop healthy roots. After trimming, place your petunias in new soil. They will need some time to adjust, but at the end of the day, you won’t be disappointed with the results.

5. Fertilizer Burn

Application of too much fertilizer in the soil can cause the tips and stems of petunia leaves turning brown. Excessive fertilizer promotes salt build-up in soil which results in this sort of damage. This condition is also known as fertilizer burn or tip burn.

You might be wondering how fertilizers are burning my leaf tips. This is how it works.

Salt build-up caused by over-fertilizing creates an artificial drought condition by blocking water to penetrate plant roots. You may observe this condition both in pot planting and landscape gardening. This is the main reason behind your petunia plant tip turning brown.

Control Measure

In the landscape, conditions try to water your plant as much as possible. This will wash off the salt build-up. You may need to repeatedly practice this to see results.

If you have planted petunias in pots, then don’t forget to keep checking your drainage hole. Salts can block these holes causing further destructive situations for your plant.

Choose your Petunia fertilizer wisely. Go for a gentle dose with an adequate amount of nutrients in it. (Our Pick: J R Peters Inc Jacks Classic Petunia Feed)


In this article, I have tried to put together the issues related to brown leaves in the petunia plant. Let’s sum up now, what causes brown leaves on petunia and how can you deal with them?

Well, just keep everything simple. Maintain a proper watering schedule, check for fungal and pest attacks and take a look at the environmental conditions.

But don’t only take my word for it. You know your plants better. Observe what they actually need and come back to us for suggestions.

Don’t hesitate to share anything about the article in our comment section. Your words can be a good uplift for my next writing. Happy gardening mate!

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