Tomatillo Leaves Turning Yellow

Native to Mexico, tomatillos or husk tomatoes make a lovely addition to a salsa verde, soups, or roasted as a side dish. However, tomatillo leaves turning yellow can lead to worries if the plant can be saved and whether you’ll have any tomatillos to harvest. 

There are many reasons for tomatillo leaves turning. You’ll learn about all of these below and also how you can save your plant (if possible). 

Reasons Why Tomatillo Leaves Turn Yellow 

Your tomatillo leaves could be turning yellow because of one of these reasons: 

Reason 1: Overwatering Your Tomatillo 

A common reason your tomatillo leaves are turning yellow is because of too much water. By overwatering, the soil becomes waterlogged and the roots of the tomatillo plants can’t absorb sufficient nutrients like magnesium from the soil. Magnesium is essential for the chlorophyll molecule to ensure the leaves are green. 

Can you save your tomatillo plant from being overwatered? 

You can usually save your tomatillo when you’ve overwatered. 

Steps to Save the Overwatered Tomatillo Plant  

When you see the leaves yellowing on your tomatillo and you’ve watered it too much or it rained a lot in your area, immediately stop watering the plant. 

Let the soil dry out for a few days, a week, or more. To check if the topsoil is dry, stick your index finger into the soil closest to where the tomatillo is planted in the soil. The soil should feel dry up to your middle knuckle.  

Tomatillos are quite drought-tolerant. Ideally, they only need an inch of the topsoil to be watered weekly. 

Reason 2: A Nitrogen Deficiency in the Soil 

Another reason your tomatillo leaves are turning yellow could be a nitrogen deficiency. If there isn’t enough nitrogen in the soil, the plant lacks chlorophyll so the leaves turn from a vibrant green to yellow. 

Can you save your tomatillo plant from a nitrogen deficiency? 

You can save your tomatillo if there is a nitrogen deficiency.  

Steps to Save the Nitrogen Deficient Tomatillo Plant  

A quick fix is to add some general purpose liquid fertilizer. Read the label on the container and use the recommended dosage as indicated. 

Alternatively, you can also plant beans or peas near the tomatillo. These are nitrogen-fixing plants and they add nitrogen to the soil. So this is a non-chemical solution, but the process takes a bit longer than adding fertilizer and you may only see results in the next season.   

Reason 3: A Magnesium Deficiency in the Soil 

A lack of magnesium can also cause the leaves of the tomatillo plant to yellow. Like nitrogen, magnesium is important in the production of the chlorophyll molecule. Porphyrin aids in the photosynthesis process, giving the tomatillo leaves their unique green color.  

Can you save your tomatillo plant from a magnesium deficiency? 

If there is a magnesium deficiency in the soil, you can save your tomatillo. 

Steps to Save the Magnesium Deficient Tomatillo Plant  

Add a teaspoon of Epsom salt that’s diluted in a quarter gallon of water to the soil. Pour the mixture into a spray bottle and fine spray the leaves every two weeks. The leaves can quickly absorb the magnesium. You can also spray the soil with the Epsom salt mix.    

Reason 4: Downy Mildew on Your Tomatillo

If you see yellow spots on the leaves on the upper layer of the tomatillo plant, then downy mildew could be the culprit. Look at the underside of the leaves. You’ll see that the bottom leaves are covered in white or grayish cotton-like growth. 

Can you save your tomatillo plant from downy mildew? 

You might be able to save your tomatillos if you see yellow spots on the leaves. 

Steps to Save the Mildew-Infected Tomatillo Plant  

To save the tomatillo from downy mildew, first prune overgrown stalks to improve air circulation – especially if the tomatillos are planted on a small area and overcrowded. This will ensure air dries up any moisture on the plant leaves (which is how downy mildew spreads) and eliminate humidity. 

Downy mildew will disappear from the plants once the weather warms and the airflow improves, so it is best to just wait.  

Reason 5: Psyllid Yellows on Your Tomatillo 

If your tomatillo is infected by psyllid yellows, also called the potato or tomato psyllid, you’ll see that the edges of the leaf are turning yellow. Psyllids are sap-sucking insects that feed on the nutrient-laden liquids in plant tissues or leaves.   

Can you save your tomatillo plant from psyllid yellows? 

You can usually save the tomatillo plant if it’s been infected with psyllids. However, in severe cases, your plant could become misshapen and die. 

Steps to Save the Psyllid Yellow Infected Tomatillo Plant  

Thoroughly drench your plant weekly with neem oil or wash with insecticidal soap to kill the psyllids, but before you treat the plant, make sure the insects are active on the plant.   

Reason 6: Tobacco Mosaic Virus or Tomato Mosaic Virus 

The tobacco mosaic virus (TMV) is a disease that infects nightshade plants, like tomatoes, tomatillos, and tobacco. The most characteristic symptom of TMV is a yellow-green molting on the plant’s leaves, but the leaves and flowers may also be distorted, smaller than normal size, or curled.  

The tomato mosaic virus is just as contagious as TMV and has similar symptoms as the tobacco mosaic virus. If your tomatillo is infected with the tomato mosaic virus, you’ll see the tell-tale signs of yellow-green mosaic patterns or molting on the leaves. The tomato mosaic virus doesn’t often kill the host plant, but the disease does decrease the quality and quantity of fruit the plant bears.  

Can you save your tomatillo plant from these viruses? 

If your tomatillo is infected with TMV or the tomato mosaic virus, then unfortunately, you can’t save your plant. The viruses are highly contagious and spread easily. Even just brushing against an infected plant means you carry the infection with you, so it can spread to any other susceptible plants you may touch or brush against.  

There are no chemical solutions to treat TMV or the tomato mosaic virus. The tomato mosaic virus can survive in the plant’s soil and debris for two years. 

So to get rid of these viruses and decrease the risk of contaminating your other plants, dig up the infected plants and burn them. Sanitize any equipment you use and thoroughly wash your hands. 

Don’t plant tomato plants or other plants that are susceptible to getting TMV or the tomato mosaic virus in the same area for at least two years.  

The Last Yellow Tomatillo  

Knowing what causes tomatillo leaves turning yellow ensures you can take preventative measures where necessary: 

• Don’t overwater tomatillos. Only an inch of water every week is enough. 
• Plant nitrogen-fixing plants that are compatible with the tomatillo.
• Take preventative measures to ensure you don’t have issues with downy mildew by watering the tomatillo from below and that no water sits on the leaves. 

And if you can’t take preventative steps, then curative steps are next: 

• Spray the tomatillo with an Epsom salt solution if there is a magnesium deficiency.
• Spray the tomatillo with neem oil or insecticidal soap if you spot psyllids. 

And if TMV or the tomato mosaic virus is at play, take care to not spread the disease, burn the infected plants, and sanitize the tools you used and your hands.