Why Are the Mint Leaves Turning Yellow?[7 Causes & Treatment]

Mints are one of the easiest herbs to grow because they are very hardy and they don’t require much maintenance. However, occasionally they fall victim to some conditions and start showing some symptoms. Yellowing of the leaves is one of them.

By identifying the problems early you can solve them and prevent the mint leaves from turning yellow. Knowing the right reason is very important. Because if you don’t take the right approach you might end up hurting your precious mints.

So, why are the mint leaves turning yellow?

7 Problems cause the yellow leaves including Imperfect Watering, Incorrect Soil, Nutrient Deficiency, Light and Shade, Humidity and Temperature, Insect Attacks, and Diseases.

In this article, I’m going to discuss these problems and tell you about how to solve them.

So without making any delay let’s get started-

7 Reasons for Mint leaves Turning Yellow-Solution

1.Imperfect Watering On Mint

Imperfect watering is one of the main causes of the mint leaves turning yellow. Overwatering and Underwatering both can bring this same result.

When the mints are over-watered their roots get choked. So proper nutrient movement is hampered. As a result, the leaves turn yellow and brown. Overwatering also brings many fungal problems which cause the leaves to turn brown and black.

When you underwater your mints they also turn yellow as well as black. The leaves start falling off for lack of enough water. Both over-watered and under-watered conditions can kill the mints if it continues for a while.

Control Measure 

Proper watering can revive the yellow mint leaves. So, it is best to check the soil moisture with a moisture meter to avoid killing your plant (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden).

Check the soil before you start watering. The watering schedule may vary depending on the soil moisture of your mint. 

If it is humid weather then water at 3 or 4 days intervals. If the weather is cool then water once a week.

Mints have an exposed root system so if you are growing mints in pots make sure the pot is large enough for the roots to grow. Make sure you keep enough drainage holes in them. 

You can also place the pot on a tray filled with pebbles. Water the pebbles and the roots will uptake water from there.

2. Incorrect Soil 

Wrong soil can also be the reason why your mint plants are turning yellow. Mints have a very delicate root system. So, they require soil that is light and well-drained. 

Clay soil holds quite the moisture and starts over watering issues. On the other hand, Sandy soil doesn’t retain much water and brings up underwatering issues. 

Control Measure

The soil needs to be loamy and fertile for your mints. Use a good potting for  mint plants (our pick: Espoma Organic Potting Mix)

Make sure the soil doesn’t hold too much moisture. Also, it should not drain moisture too fast. To improve the soil drainage add organic compost or perlite(our pick: Miracle-Gro Perlite). Once the soil problem is fixed the new green leaves will grow.

3. Nutrient Deficiencies of Mint

Nutrient deficiency is another reason behind the yellowing of mint leaves. Some deficiency makes the lower leaves yellow and some other deficiency makes the upper ones yellow.

Even over-fertilization imbalances the soil. Overdose of fertilizer burns the leaves which cause the mint leaves to turn black and curl up. 

Mints thrive when the pH is between 6.5-7. The deficiency or addition of any nutrients changes the pH range. So before fertilizing check the soil pH with a pH meter.

Control Measure

Make sure you don’t use any chemically toxic fertilizer. Apply the best all-purpose fertilizer to your mints that are specifically made for herb plants (our pick: Jobe’s Organics Herb Plant Food).

If you have potted Mints in the same pot for several years then repot them in fresh soil. It’s better to use clay pots than plastic pots for good drainage.

4. Light and Shade on Mint

Mints are grown both indoors and outdoors so one might wonder does mint prefers sun or shade?

Well, mints are sun-loving plants. They need at least 6 hours of sunlight every day. Too much shade turns their leaves yellow. 

But if they are exposed to the sun in extreme conditions for a long time then the leaves start to get sunburnt. In this case, the mints either can turn yellow or brown.

Control Measure

Plant your mints in a sunny location. Make sure your indoor mints get full sun exposure, You can place them by the window where they can get sun or move outside for a few hours. If there is not enough sunlight available and your potted mint plant is still yellowing then consider using indoor grow lights (our pick: GrowLED LED Indoor Garden)

5. Humidity and Temperature

High temperatures can burn your mint plant resulting in yellow leaves. Also, mints don’t grow very well in humid conditions. 

Both reasons can occur as an environmental shock. As a result, The leaves turn yellow and brown. 

Control Measure

You need to regulate the temperature between 70-85°F. While you can’t control nature but if you are growing mints indoors then you can get a humidifier to control the humidity to prevent them from turning yellow.

In the case of outdoor mint plants if the weather is very extreme give them partial shade. If possible relocate them into a cooler place but make sure they get enough sunlight in the morning. Increase watering in extreme weather conditions by checking the soil moisture with a meter.

6. Insect Attack On Mints

Aphids, Thrips, and spider mites feed on the mint leaves and suck up the nutrients. Their feeding makes the leaves turn yellow and even brown too. All these insects are very tiny and hard to notice until they start any severe infestation.

Aphids attack Vietnamese mints particularly and also cause curling up and black spots on leaves. It is critical to kill these pests to save the plant. Otherwise, these pesky ones transmit viral diseases which can be fatal to your mints

Control Measure

Mints are cooking herbs so before choosing any chemical insecticides we have to make sure they are safe. Apply the best organic insecticide on your mints so the leaves are protected (our pick: Monterey Garden Insect Spray)

You can also spray neem oil and insecticidal soap (our pick: Natria Insecticidal Soap)

I have included some natural homemade recipes. These are easy to make and very effective against aphids and other pests. Check them out below:

#Recipe 1:- Basil Tea Recipe

Ingredients:

  • 1 Cup of fresh basil
  • 1 teaspoon of liquid dish soap
  • 2 cups of water

Steps:

  • Let the water boil in a pot and then remove it from heat
  • Add the basil leaves to the pot and cover it with a lid.
  • Keep the lid closed and wait for a few hours
  • Strain the basil leaves from the water.
  • Lastly, add the liquid dish soap and put the mixture into the sprayer bottle
  • Spray it 2-3 times a week.
  • It’s very effective against aphid infestation for your mints.

#Recipe 2:- Tomato Leaf Spray Recipe

Ingredients:

  • 1 cup of chopped tomato leaves
  • 500 ml of water
  • Few drops of liquid dish soap

Steps:

  • Add the chopped tomato leaves to water and let it soak overnight.
  • After that, Strain out all the tomato leaves 
  • Mix with dish soap and put into the sprayer bottle.
  • Spray it on the mint leaves twice a week. 

Note: Any new homemade recipes should always be used in a small leaf first. If the leaf burns or discolors then add some water to the solution to dilute. And then apply again into a small leaf. If the leaf is okay then start spraying them on your mint plant.

Preventive Measure

Do not over-fertilize the soil with Nitrogen. Because this attracts more insects. Keep an eye on the soil. If it stays dry for too long spider mites can infest.

Don’t apply insecticides when the sun is scorching. This can burn the mint leaves and turn them into black.

7. Diseases of Mints

Fungal and viral diseases damage many herb plants including mint, cilantro, basil, and pepper. The diseases that cause yellow mint leaves are Verticillium wilt, Mint rust, and Cucumber mosaic virus.

Mint rust is a particular disease in the family of mint plants. It affects sweet mints, peppermint, and spearmints a lot. It causes severe stunting and yellowing of leaves. The spots also turn brown in the later stage. Eventually, the mint leaves start falling off.

Verticillium wilt is one of the most common diseases of mint plants, especially apple mints. This disease causes the lower leaves to turn yellow with brown spots. It also makes the leaf edges brittle and dry. 

The cucumber mosaic virus is not that common. But aphids can easily transmit this disease to your mints. The leaves get yellow mosaic-like dots on them. Gradually the entire leaf turns yellow.

Control Measure

Remove the infected yellow leaves and dispose of them carefully away from your garden. Then you need to apply a good fungicide to rescue your mints.

But there are so many fungicides available in the market. You need to pick one that is herb-safe (our pick: Bonide Copper Fungicide) Make sure you always follow the directions carefully and note when it’s safe to harvest your mints after the fungicide application.

But sadly there is no cure for the mosaic virus. The best thing you can do is prevent this virus by killing the aphids and pests with insecticides.

Here are some home remedies that are practical for fungal problems and very easy to make. You can try these recipes below:

#Recipe 1:-Cinnamon Spray Recipe

Ingredients:

  • 3 Tablespoons of Cinnamon
  • 2 Liters of water

Steps:

  • Add water and cinnamon together and shake
  • Let it sit for a few hours or overnight
  • Strain the mixture with a fine cloth
  • Put the mixture into a spray bottle
  • Spray it on your infected mint leaves twice a week until the problem solves.

Recipe 2:-Baking Soda Spray Recipe

Ingredients:

  • 2 teaspoons of baking soda
  • 1 teaspoon of dishwashing liquid
  • 1 teaspoon of any cooking oil 
  • 2 liter of water

Steps:

  • Add baking soda and cooking oil to a mixing bowl and add the liquid soap
  • Then mix with water and stir slowly
  • Then pour it into the sprayer.
  • Spray on both sides of the infected mint leaves up to twice a week.

Preventive Measure

Fungal problems occur in damp places where airflow is less. So make sure the mints have enough space around them. Prune off some old leaves to provide good airflow.

Wash the garden tools after working with them. Keep other infected plants away from your mints. Water the mints in the base during the morning so the leaves don’t stay wet. 

Frequently Asked Questions (FAQs)

Can yellow leaves turn green again?

If the yellow leaves are due to wrong watering or poor humidity then the leaves can turn back green again once the watering and humidity problem is fixed. But if it is due to sunburn or diseases then the yellow leaves will not turn green.

Does Mint need a lot of water?

Mints need an average amount of watering. They love moist soil. So watering every 1 or 2 days in hot summer is enough. And during spring and winter water every 3 or 4 days. During the rainy season, they won’t need any additional watering.

Can I eat yellow mint leaves?

If the yellowing is due to water problems or nutrient deficiency then you can eat them after properly washing them. But if the yellowing is caused by fungal and viral diseases then you definitely should not eat them. Diseased leaves will have a bad smell.

Conclusion

Mints are very fast-growing herbs. Keep them hydrated and let them enjoy the sun. Take care of the pests and disease problems with proper insecticide and fungicide. The yellow mint leaves will revive themselves and will turn out to be stunning green.

I hope this article helped understand what to do with your yellow mint leaves and how to treat them. You can treat your basil or cilantro plants in the same way too.

If you have any further questions ask away in the comment section below and share this article with your friends if they have this same problem.

Leave a Comment