9 Causes of Yellow Leaves On Petunia [Practical Solution]

“Summer is coming, so does Petunias. But I am not happy.” Well, that was the exact scenario of my last summer. Suddenly, I had noticed yellow leaves on My Petunias & that did make me worried & a little bit peeved too.

However, I went to several experts, stormed at google & found out that with a bit of care, you can save your Petunias by yourself, even with homemade remedies!

Today, I am going to share my last year’s lessons with you. It’s easy, you have to be a little careful & active, that’s all.

So, If you are thinking about why do petunias go yellow, here’s a brief- the main reasons are nutrient deficiency, problematic soil, improper fertilization, watering problem, sunlight issues, transplant shock & pest attacks. Now, without further ado, let’s check out the details-

Why Do Green Leaves Turn Yellow?

Petunia leaves show different types of yellowing. For example, yellow leaves with dark green veins, yellow edges of leaves, irregular yellow patches on the leaves, etc. So, what is the primary cause for yellow leaves on Petunia?

You know that leaves contain a pigment called chlorophyll which is responsible for their dark green color. Whenever leaves lose the chlorophyll abundance or, chlorophyll production gets disrupted, leaves show unexpected discoloration like yellowing, browning, etc.

Why Are Petunia Leaves Turning Yellow- Reasons & Solutions

1. Nutrient Deficiency

Iron & Magnesium are two prominent nutrients involved in chlorophyll synthesis. Often a deficiency of these nutrients causes leaves to turn yellow & the phenomenon is referred to as Chlorosis. But apart from Fe & Mg, petunia leaves are also sensitive to the deficiency of N, K, S, Mn, B & Mg.

Causes & Symptoms

Let me walk you through various types of symptoms so that you can identify which nutrient is lacking on the soil-

  • Yellowing of new leaves with dark green veins (Fe deficiency).
  • Yellowing of lower leaves from leaf lip & necrosis (Mg deficiency).
  • Yellowing of inmost & aged leaves & yellowing progresses outward (N deficiency).
  • Yellowing of leaf tips & edges with dark green middle leaf area (K deficiency).
  • Yellow specks between leaf veins with extended holes (Mn deficiency).
  • New leaves with pale green or light yellow coloration (S deficiency).
  • Yellowing of lower leaf tips (B deficiency).

Control Measures

Obviously, the immediate action should be fertilizing your Petunias. In that case, choose a Petunia fertilizer that provides both macro & micronutrients and assures both instant & long-term feeding. (Our Pick: J R Peters Inc Jacks Classic Petunia Feed)

But, if there is a lack of particular nutrients, you can think of providing that nutrient only. For example, Epsom salt is highly effective against Mg & S deficiency while micronutrient powder will recover the lack of Fe, Mn, B, etc.

Furthermore, here is an excellent homemade remedy for the yellow leaves of your Petunias. Try this formula once & thank me later.

Homemade Fertilizer For Petunia

Required Components:

  1. Mustard Cake
  2. Water

Making Procedure:

Add 500g mustard cake in 5L of water in a bucket & have it covered for 96 hours to attain proper fermentation. But don’t forget to stir the mixture a minimum of two times a day.

After 96 hours, you have your stock solution. Now, take half a liter of the blend & add it to another 5L of water. Stir & mix properly, and there you go.

Applying Method

For perfect action, drench the soil with 100 ml of the fertilizer & re-apply after 15 days.

Preventive Measures

A good practice for gardeners is to test the garden soil at least once a year. Thus, you can actually get the nutrient status of the soil & take action accordingly.

2. Soil Problem

Most of the reasons behind your Petunia leaf yellowing originate from the soil in which it is growing. So, what kind of soil does Petunia love?

Well, Petunia thrives in well-drained sandy soil which remains moist evenly. Experienced growers have found that continuous dry soil is primarily causing the yellowing of Wave Petunia leaves.

Moreover, Petunia loves acidic soil with a pH range of 6-6.8. Plus, organically rich soil boosts up both the color & number of Petunia flowers. That’s why expert gardeners add a minimum of 25% organic matter during soil preparation.

Therefore, if your soil lacks any one of the above, you have a problem to fix my friend.

Causes & Symptoms

A poorly drained soil stays waterlogged which results in root rot & interrupted nutrient absorption. Similarly, alkaline soil prevents several nutrient uptakes such as Fe, Mg, etc.

In these cases, Petunia fails to uptake necessary nutrients for its growth, flowering, chlorophyll production & so on. Thereby, stunted growth, leaf yellowing, poor flowering, etc show up.

Control Measures

Once you have planted, there is nothing much to do with problematic soil. All you can do is water adequately & keep adding organic matter from time to time.

Preventive Measures

To fix yellow leaves on Petunias, prepare your soil perfectly so that Petunias love the medium. Therefore, you can buy a suitable potting mix from here (Our Pick: Espoma Organic Potting Mix) or make it at home by adding 50% garden soil, 20% coco peat, 20% cow dung & 10% vermicompost together.

3. Over-Fertilization

If there is one thing that is totally prohibited for Petunia care, it must be over-fertilization. Though Petunias are heavy feeders, that does not mean they are in love with obesity. Just kidding!

Causes & Symptoms

Too much fertilizer toxifies the soil & causes root rot. Thus, Petunia faces difficulty in uptaking nutrients. During such a phenomenon, Petunia shows stunted growth, wilting, burned leaf margins, leaf yellowing, etc & in severe cases, death is pretty much obvious.

Control Measures

First of all, stop fertilizing. And then drench the soil with adequate water so that the fertilizer gets washed away.

Preventive Measure

Always stick to the direction of the product label. Every fertilizer company encloses the necessary directions like when to use, how to use, how much to use, etc with the product. So, read the label carefully & follow it precisely.

4. Over-Watering

Overwatering is a common mistake that causes leaf yellowing of potted or hanging basket Petunias. You know, there is a subtle difference between caring for a potted & an in-ground plant. Whenever you fail to adjust with this, you over-water.

Causes & Symptoms

A 100% perfect drainage may not work when the soil gets waterlogged. In that case, water molecules replace soil oxygen, cause root rot & enhance fungal infection.

Thus, Petunia fails to uptake fluid & nutrients for chlorophyll synthesis & has trouble while breathing, I mean respiration.

Control Measures

Saving a waterlogged Petunia is tough, but quick action may create a chance. All you have to do is get your Petunia out of the pot, dry the root ball by keeping it in the sun & wrapping it with paper to absorb water.

After that, repot your Petunia & stay careful about over-watering.

Preventive Measure

Petunias are pretty much drought tolerant. It may need frequent watering during the growing & blooming season but, the rest of the time, watering once a week is fine.

You know what? Leave it. Just follow the thumb rule- “Water only when the topsoil is dry & keep watering until water comes out through the drainage holes.”

However, you can check the soil moisture by putting your finger 2-3 inches deep into the soil or use a moisture meter (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden) to get accurate measures.

5. Improper Sunlight

Too much or too little, both types of sunlight can cause yellow leaves of Petunias. As sunlight is the only energy source for plants, it must be accurate, right?

Causes & Symptoms

Due to the lower amount of sunlight, Petunia gets trouble during photosynthesis which affects chlorophyll production. You may notice yellowing of inner leaves where sunlight hardly reaches.

On the other hand, excessive light causes the burning of leaves. In that case, leaves initially turn yellow & end up as burned brown leaves.

Control Measures

If your Petunia is not getting enough light, move it to a place where it will get 5-6 hours of direct sunlight. But during excessive heat, Petunias won’t mind a partial shade.

Preventive Measure

Sunlight is not something that we control. So the best you can do is, grow a native variety in the first place & make sure it gets sufficient sunlight.

6. Transplant Shock

Whether it is due to waterlogged soil or root bound issues, transplanting does need some skills. Otherwise, a bad transplant can lead your Petunias to death. Moreover, transplant shock is a common reason behind Petunia seedling leaves turning yellow.

Causes & Symptoms

After transplanting, Petunia seems to show a lagging phase to adjust to the new environment. Sometimes it comes up with leaf yellowing. Though it is pretty much usual, a prolonged shock period is something worth worrying about.

Control Measures

There is nothing much to do while your Petunia is going through a transplant shock. It should revive by itself. And leaf yellowing is not really an issue at that time.

Preventive Measures

Make no mistake during the transplant process. Make sure minimal damage to the roots. And train your Petunia gradually to the new environment, for example, gradual exposure to the sunlight. If transplanting goes well, you won’t have to face yellow Petunia leaves.

7. Viral Infection

Once your Petunia is affected by viruses, probably the only thing to do is separate the plant from others & eliminate it. Sad, isn’t it?

Causes & Symptoms

The two most common viruses of Petunia are Tobacco Mosaic Virus & Petunia Vein Clearing Virus. These Viruses block the channel through which Petunia transfers water & nutrients all over its body.

Thus these viruses create a vulnerable internal situation for Petunia & result in stunted growth, leaf yellowing, yellow irregular leaf patches, yellowish vein, etc.

Control Measures

As I said earlier, separate the affected Petunia from others & destroy it to avoid spreading.

Preventive Measures

First of all, keep your garden & garden tools clean. Secondly, keep your plant protected from insects that transmit the tobacco mosaic viruses, for example- aphids. And finally, the Petunia vein clearing virus only spreads through grafting. So, if you are thinking about grafting, make sure the scion is healthy & disease-free.

8. Insect Attack

The common insects of Petunia are aphids, spider mites, thrips, caterpillars, leafminers, bugs, etc. Not all of them cause leaf yellowing. Mainly, insects that feed cell sap cause yellow spots on Petunia leaves. And common sap-sucking insects are aphids, spider mites, thrips, etc.

Causes & Symptoms

Sap sucking insects feed the cell sap & reduce the chlorophyll content of the leaves. Thus it creates a yellow spot around the sucking point.

Though it is not easy to identify these tiny insects, here are some tricks that you can follow to identify them-

Look for sticky substances at the downside of the leaf as aphids produce honey while feeding. Spider mites create silky waves near the leaf edges while thrips can easily locate through an unaided eye.

Control Measures

Pick up the best insecticide (our pick: Monterey organic Garden Insect Spray) for your Petunia & start applying. But you can also apply some easy-to-make DIY petunia insecticide to kill these unwanted guests. Here are some suggestions-

The Miracle All In One Insecticide

Ingredients:

  1. Yeast powder
  2. Boiled rice
  3. Molasses
  4. Curd
  5. Water

Procedure:

  1. Add 50g yeast powder, 100g boiled rice, 200g molasses & 100g curd into 5L of water. Mix it properly & leave it to ferment for 7 days.
  2. Stir the mixture once every day & after 7 days, filter the liquid and get a freshly brewed insecticide for your Petunias.

Smothering Neem Oil Insecticide

Ingredients:

  1. Water
  2. Neem oil
  3. Liquid dish-washing soap

Procedure:

Add 1 tablespoon of neem oil & 1 tablespoon of liquid soap with 1 gallon of water. Mix or shake properly & voila!

Preventive Measures

It is best to treat your Petunia with proper insecticides before the insect attack. Plus sticky traps are great equipment to reduce insect attacks.

9. Fungal Attack

I don’t think a plant can have anything worse than a fungal attack. Funguses wreck the plant badly & destroy its external beauty, especially flowering plants like Petunia. For fungal attacks, leaf yellowing is just the start of severe damage.

Causes & Symptoms

Petunia is susceptible to multiple fungi. But the most responsible fungi for leaf yellowing are Verticillium dahliae & Verticillium albo-atrum. These two variants cause Verticillium wilt of Petunia.

Sadly almost every variety of Petunia like Mexican Petunias, Waving Petunias, Night sky, Black Velvet, Petunia Bravo, Cascadia Petunia, Prism Petunia, Pink Star Charm, Shock Wave, Grandiflora, multiflora, etc are highly susceptible to these fungi.

Now you may ask, how do fungi cause leaf yellowing? Well, first of all, they block the water-conducting system of Petunia to have water & nutrients for their own growth. Thus they make a deficiency of water & nutrients which eventually results in wilting & yellow edges of Petunia leaves.

Control Measures

Sorry to say but, it’s not easy, close to impossible. The best you can try is spraying the best fungicide immediately (Our Pick: Bonide Copper Fungicide)

Preventive Measures

Firstly, solarize the soil to eliminate every fungal spore. You can use a soil fungicide too. Secondly, plant a disease-free petunia. Thirdly, keep your Petunia healthy by taking good care. And finally, make sure that your garden tools are clean & keep your garden clean too.

However, it is kind of obvious to use fungicide for a better Petunia display. So, to make it easier here is an effective homemade fungicide recipe for you-

Bio-Fungicide of Baking Soda

Ingredient:

  1. Baking Soda
  2. Dish-washing Liquid
  3. Olive oil
  4. Water

Procedure:

Add 1 tablespoon of each three ingredients into 500 ml water & mix properly. Your fungicide is ready to use.

Final Words

An eye-soothing Petunia display suits with healthy green leaves, not with yellow ones. I know leaf yellowing is pretty common but that doesn’t mean you leave it unattended.

However, leaf yellowing is a sign that your Petunia needs some care immediately. Well, now you know what can possibly get wrong & how you can take care of light green or yellow leaves on Petunias.

So, don’t wait up. Be a plant doctor. Look out for all the probable factors & treat them accordingly. Have a nice day.

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