5 Causes of Petunia Leaves Turning White [Control & Prevention]

Petunias are quite popular among gardeners for their bright blooms. Grown as annuals these have been an easy pick for gardeners to decorate their land. But most of the time petunias suffer from different issues. Leaf turning White is a common issue of concern

Before taking any action; you should know why are the petunia leaves turning white? 

The green leaves of Petunia can be white for different reasons such as powdery mildew, pest infestation, fertilizer burn, sunburn, and low light. 

But don’t worry, you can combat such issues with proper management. And I am here to help you with the step-by-step guide for getting rid of Petunia leaves turning white.

So, without further ado, let’s dive into-

How to Fix White Leaves in Petunia

1. Powdery Mildew

If you are observing some kind of white powdery substances on affected petunia leaves, this can be because of powdery mildew, a common form of fungus.

These basically develop on plant leaves in a flaky form. Sometimes this sort of mildew can also leave a coating on leaves. So, it’s quite easy to detect them.

Control Measure

You should treat powdery mildew as soon as possible as this spreads super fast to other plant parts. If not treated properly this can affect your petunia buds. If you are wondering how to treat powdery mildew on petunias, let me help you.

Remove the affected leaves carefully Pick a mild fungicide specially formulated for ornamental plants and spray both the upper and lower sides of the leaves (Our Pick: Bonide Copper Fungicide)

You can also look for a neem oil-based fungicide. It’s safe for ornamental plants. (Our Pick: Garden Safe Home-pest-Control-sprayers)

Home Remedies

#Recipe 1: Baking Soda Mixture


  • 5 tablespoons of baking soda
  • 5 tablespoons of vegetable oil
  • 5 teaspoons of bleach-free dish soap
  • 5 gallons of water


  • Add baking soda and vegetable oil together
  • Mix this with water and add liquid dish soap
  • Pour this into a spray bottle and apply it to your foliage

#Recipe 2: Milk Spray


  • 1 liter of milk
  • 10 liters of water


  • Mix milk with the proper amount of water
  • Spray this on your plant

Preventive Measure

By adopting some measures you can save your plants from powdery mildew.

At first, try to look for a mildew-resistant variety. You can collect them from local cultivars.

Always provide a balanced nitrogen dose. Don’t go overboard with the same kind of fertilizers always.

At last, prune your plants often to provide proper air circulation. This will reduce the chance and severity of any kind of fungal attack as well as powdery mildew.

2. Pest Infestation

Pest infestation occurs quite often in floral plants. You need to be careful about the beneficial insects also as these are necessary for pollination.

However, pests are associated with fungal attacks most of the time. This causes the whitening of leaves. So you should keep checking for pests in your petunias.

Aphids, thrips, and scales are common pests for Petunia. Feeding of these insects can cause white spots on petunia flowers and leaves. You can easily diagnose pest attacks by these spots.

You may also find some white bugs in petunia plants. These are the mealybugs that suck out juice from plant leaves.

Activities of these pests can promote a fungal attack on your plants. So, it’s better to take steps to control them.

Control Measure

Start by splashing some water on your petunias. This will primarily remove pests and feeding substances adhering to plant leaves.

Insecticidal soaps or Neem oils are quite effective in repelling unwanted insects. I would like to suggest any pesticide at the last level of defense. But be careful about choosing yours as some can kill beneficial insects. So, here is a safe option (our pick: Monterey organic Garden Insect Spray)

Home Remedies

#Recipe 1: Soap Spray


  • 3 teaspoons of castile soap
  • 2 liters of water


  • Mix castile soap in water
  • Pour this into a spray bottle
  • Apply this to the plant surface

Caution: Don’t use any soap with high bleach content. This may damage your plants.

#Recipe 2: Garlic Spray


  • 4 whole garlic bulbs
  • A cup of vegetable oil
  • 1 liter of water


  • Grind garlic to make a paste.
  • Add vegetable oil to this.
  • Add water to it and strain.
  • Use the liquid as a spray for your plant.

Preventive Measure

To save your petunias from pests you can plant some marigold or venus fly traps in your garden. These are a great repellent to pests and also an attractant for pollinators.

3. Fertilizer Burn

Over-fertilizing is never a good practice. But unfortunately, most gardeners end up with doing such a mistake.

Excessive fertilizers can cause salt to build up in the soil. This directly affects your petunia roots by burning them.

Also, the overhead application of fertilizers causes white spots in the plant. This happens because of chemical burns from these commercial formulations.

Control Measure

Choose a balanced fertilizer for your Petunia plant. The NPK fertilizer may help as it has an adequate amount of nutrients.

Be careful while putting mulch. Sometimes there can be a high content of nitrogen in mulch which can promote salt build-up.

Avoid fertilizers to touch the aboveground part of your petunias, especially leaves and flowers. Make a wet formulation out of dry fertilizer, this will reduce damage.

4. Sunburn

Excessive sun exposure can damage plant chlorophyll. This will gradually turn your leaves white. Mostly in plants like petunia, sunburn is quite common. You can also observe some right after transplanting. This occurs due to transplant shock.

Bleached-out white leaves are common results of sunscald or sunburn. If this is not treated properly, your plant leaves can fall off in the long run.

Control Measure

As most transplanted plants face sunburn issues more often, let me show you a trick how. Simply transplant your petunias in a pot. Provide sunlight only in the morning for some days. Then gradually increase the period of time.

After that, you can place them in the landscape. By this period of time, these will reach to a certain maturity level to withstand extreme sunlight.

5. Very Low Light

In partial light indoor plants can suffer from white leaves issues. Other associated symptoms may include long leggy growth and weak stems.

Basically, the absence of light causes a reduction in plant green pigment, chlorophyll. As a result plant leaves turn white.

Control Measure

First of all, place your plant where there is enough sunlight.

Also, provide proper spacing to allow light penetration. You can keep pruning unnecessary plant parts.

Last but not the least; try to maintain a proper pH in your soil. A soil pH meter may help you (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden)


Here I have tried to provide a guideline on how you can deal with problems related to white leaves on petunias. Hope you have got an idea of how you have to work with your plants.

Just a few simple steps, maintain your plant health with a bit of care, look for diseases and pests and follow the instructions provided and you are good to go. Not that hard actually.

Come back to us if you need any help. You can comment about your experience or ask about other issues. Happy growing. 

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