5 Reasons for Mint Leaves Turning Black [Causes & Treatment]

Mint is one of the most versatile herbs on this planet. You can use it in your savory dishes, in desserts, and even in drinks. They are known for their stunning and delectable aroma and the freshness it brings to the surroundings.

Reasons for Mint Leaves Turning Black

Although mint is favorably easy to grow, you need to understand that this thick and bushy green foliage can turn black if optimal care isn’t delivered. If you notice the leaves turning black, the good news is that with a few control measures, you should be able to revive the plant without any issues.

We will highlight more on that and how you can fix the issues with some simple measures.

Why are Mint Leaves Dying and Turning Black?

If you grow mint in your garden, you likely know how beneficial the plant is. Not only does it impart a fresh aroma, but it also helps in keeping the nearby plants safe and pest-free to an extent.

But, in the process, several factors could end up damaging the mint plant itself. Following are some of the potent reasons why.

1. Watering issues

Environmental and water stress are two of the most common issues that contribute to the discoloration of the leaves and the eventual death of the plant. It’s not any different with the mint leaves as well. Mint plants need a high-quality and water-draining soil mixture. If there is a chance of water-logging in the soil, be assured that the same will lead to the discoloration of the leaves.

Watering issues

When the soil is waterlogged, it affects the root system first, leading to risks of root rot. Your aim with the mint plant is to ensure that the soil is well-drained but moist at the same time. Dry soil with lacks moisture will have negative implications on the plant as well.

Mint leaves experience a gradual change of color in their leaves. It typically starts with yellow, which then turns to black.

How to fix it?

A moisture meter is your best friend in this case. Not only does it provide an accurate moisture level reading, but it also alerts you about when you need to water the mint plant and when you shouldn’t.

2. Improper soil conditions

As we mentioned, mint leaves need high-quality and well-draining soil for their growth. Since they have a very sensitive and delicate root system, look for soil that is fertile and loamy. This kind of soil composition also keeps the nutrient balance in check, which is crucial for the growth of the plant.

Improper soil conditions

Also, if you tend to over-fertilize your soil, that can lead to the leaves turning black. This is due to excess salt deposition in the soil, which eventually burns the root system and alters the nutrient uptake as well.

How to fix it?

Instead of using cheaper and chemically formulated fertilizers, switch to organic fertilizer options. They are slow-releasing and don’t impose negative impacts on the quality of the soil in the long run. Also, you might consider repotting your mint plant if the soil is overfertilized.

3. External environmental stress

Mint plants need direct and prolonged sunlight but not in excess amounts. Sunlight less than 85 degrees Fahrenheit is considered normal for the mint plants to grow in. If the temperature exceeds that, it will eventually lead to sun-related stress on the plant, something that you don’t want for the optimal growth of the plant.

External environmental stress

In other conditions, lack of optimal sunlight exposure can end up turning the leaves black as well. So, the key is to maintain a balance when it comes to sunlight exposure.

How to fix it?

Start by cutting and trimming out the black leaves that are wilting down the side of the stem. After that, transfer the pot somewhere where the plant gets 6-7 hours of sunlight and then stay in shade for the rest of the time.

4. Exclusive diseases

There are a few plant diseases that are exclusive to the mint plant. Mint rust and leaf blight are two of the most common issues that affect the growth of the mint plant and can even turn the leaf’s color to black. All of these issues are fungal infections that happen due to humid weather conditions and soil issues.

Exclusive diseases

Also, with these fungal diseases, the leaves don’t turn black entirely. Instead, the leaves first turn yellow, and then black spots appear. Alongside that, the leaves also experience curling and wilting, which are potent signs of fungal infestation.

How to fix it?

Fungal diseases are very deadly and spread at an alarmingly fast rate. This means that if you don’t take immediate action, chances are that the same will lead to the death of the plant. Fungicides work very efficiently in reducing the risks.

5. Pest infestation

Not just pathogens, you need to look out for pests as well since those lead to the blackening of the mint leaves over time. Common pests like aphids, cutworms, thrips, etc. are considered harmful to the mint leaves. Not only do they feed on the plant, but they also affect the nutrient uptake, which negatively impacts the plant’s growth.

Pest infestation

Ideally, look at the underside of the leaves since that’s where most of the aphids are. Also, if you notice holes in the leaves, that’s another potent sign of pest infestation that needs immediate intervention.

How to fix it?

Start by spraying a mix of neem oil and water on the plant to keep the insects and pests out. If the blast of water isn’t enough and the pests are still evidently available, the next thing that you can do is spray some insecticide or pesticide on the plant and wait for it to work.


Mint leaves are very susceptible to damage, so if you notice the leaves turning black, look out for the potential cause immediately before it’s too late. Sometimes, the earlier you detect the issue, the easier it gets to manage the symptoms and support optimal growth of the plant.

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