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Yellowing Petunias – Help is here!

Yellowing Petunias – Help is here!

If you are planning a garden for your yard, it is almost inevitable that there will be petunias in it. Pretty, versatile in color, and easy to care for, these pretty little flowers are delightful to look at in any setting, garden, or container.

They are annual plants, and while that means that you have to plant new ones every year, you still want them to look amazing for the year. Although easy to care for, one of the most common problems with them is their foliage turning yellow. 


Why are my petunias turning yellow?

There can be a few reasons for this. Nutrient deficiency, improper watering method, inadequate sunlight, and warmth are some of the reasons. There is also a possibility that disease either viral or fungal could be the culprit. It is also possible that pests such as aphids are the reason for the yellowing leaves on your petunias. 


Nutrient Deficiency

Petunias are a heavy blooming plant and as such need to be fertilized and fed regularly. Some of the more common reasons for a nutrient deficiency with petunias is that the roots are too compacted to get adequate nutrients and water to the plant or that they are not being fertilized often enough or with the right fertilizer. 

When you plant petunias, it is a good idea to shake the roots loose before you plant them to ensure that they are not all bunched together. Sometimes they will be twisted tightly together.

In this case, you will need a sterilized set of shears to gently clip and untwist them before planting them. If they are bunched together, the plant will not be able to feed itself properly, and consequently, the leaves will turn yellow and the plant could die. 


How often do I have to fertilize petunias? 

Petunias need to be fertilized with a balanced fertilizer every 2 to 3 weeks. I start fertilizing mine in early July and continue until the growing season is complete. Container grown petunias will do well with a time-release fertilizer but spreading ones can need to be fertilized more often. 


Can petunias be over fertilized?

Yes, they can. Unfortunately, the symptoms of over-fertilizing are the same as with under fertilizing. The leaves turn yellow and wilt. If the issue is a fertilizer with too much nitrogen, petunias will not only turn yellow, but they also won’t flower. 

If you suspect that you have over-fertilized, stop using the fertilizer immediately and don’t use it again until the plants are healthy.

Water the petunias deeply, soaking the soil down to the first 2 or 3 inches. If they are container plants, water them liberally until water comes pouring out of the drainage holes. This will flush some of the fertilizer out and help the plant to recover. 


Improper Watering 

Petunias need a fair bit of water however they do not like their leaves or petals to sit in water. The soil should be moist but not wet all the time.

It is best to use a soaker hose before the sun comes up on them to prevent the water from burning the plant in the sun and to prevent the plant itself from getting wet.

If a soaker hose isn’t an option, water close to the soil, being careful not to get water on the leaves and flowers. 


Inadequate Sunlight or Heat

Petunias need bright sunlight and warm weather to grow at their best. If there is not enough sun or the weather is too cool, they could turn yellow and wilt. 



Fungal diseases are one type of disease that can cause petunias to turn yellow and ultimately die. Petunias can get fungal infections from overwatering which can cause root and stem rot. Verticillium wilt is another type of fungal infection that causes petunias to yellow. 

If you have a few plants that have a fungal disease, you have to remove them from the rest of the plants otherwise it will spread to all the other plants and ultimately kill them all. Make sure you dig out all of the roots of the diseased plants when you remove them. 

Sometimes humidity or overcrowding can be the cause of fungal diseases. Always make sure there is room in between your plants for air to circulate. 

The other type of disease that can affect petunias is viral disease. The most common one is Tobacco Mosaic Virus. Tobacco is bad for humans, but it is also bad for some plants. It is spread through aphids and contaminated soil but also from the hands of a smoker.

This virus causes the leaves to turn a mottled yellow and it deforms the leaves and the flowers. If you are a smoker, scrub your hands before working in the garden.



Aphids can spread Tobacco Mosaic Virus from plant to plant but can also wreak havoc from feeding on the plant. They will turn the leaves yellow and cause their growth to be stunted.

The best way to treat an aphid infestation is a mix of water and insecticidal soap. Spray it on when the sun is not on the plants and the temperature is below 90 degrees Fahrenheit. 



Petunias are a pretty and easy to manage addition to any garden or container garden. They come in a variety of colors to match pretty much any color scheme.

The biggest issue with caring for them is yellowing leaves but following this guideline will prevent a lot of the common reasons for this which will keep your garden bright and vibrant all season long. 


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