Why Are My Mint Leaves Turning Brown?

Mint is one of those herbs that many people love to grow in the garden or pots. This herb is easy to grow, easy to care for, and brings many benefits in life. Mint leaves can be used as a spice in dishes or become a delicious flavor in drinks to cool down the summer. Therefore, many people grow mint plants to decorate their homes and as ingredients for many dishes.

However, one of the biggest problems you can face is mint leaves turning brown. Why are my mint leaves turning brown? Many reasons lead to the condition of the leaves of mint plants turning brown subjective factors or objective factors. To find out the detailed reasons, let’s answer them in the article below.

Why Are My Mint Leaves Turning Brown? How To Fix It?

There are many reasons why mint leaves turn brown all at once. Some of the underlying causes for this phenomenon are low humidity, improper watering, lack of nutrients, high temperatures, or fungal and insect diseases. Here are some basic causes that you need to pay attention to to prevent and fix.

Overwatering Or Underwatering The Mint Plant

One of the most common reasons why mint leaves turn brown all at once is over-watering. Mint plants prefer moist soil but do not like to be waterlogged for long periods. Soil that is too wet causes the entire roots to become waterlogged, unable to exchange air, and leads to a lack of oxygen. As a result, the root system cannot absorb nutrients from the soil which causes the leaves of the mint plant to turn brown.

Some of the basic signs that you can observe with the naked eye are brown spots on leaves, wet soil, mucus in the ground, and a rotten smell. If waterlogging persists for a long time, the entire mint plant will soften and droop to the ground.

To prevent this, you need to check the soil moisture before watering. You can use a moisture meter or use your finger to check the moisture in the soil. Only when the moisture in the soil has dried to 2-3 inches, should you water until excess water drains from the drainage hole?

Besides, lack of water is also a common cause of mint leaves turning brown. When plants do not absorb enough water, under constant sunlight, the leaves will dry out, become brittle and turn brown. Some basic signs like wilted plants, dry soil, and dry and brittle leaves. If water shortage persists for a long time, many mint plants will wilt and droop.

To overcome this situation, you need to check the moisture in the soil and timely water the plants. You should not water according to the period or schedule available, water according to the weather conditions, and the actual water needs of the plants.

Why are my mint leaves turning brown

Too Much Or Too Little Sunshine

Mint plants are cold-season plants, so they prefer full sun to grow best. However, intense sunlight for many hours will burn the leaves and cause the entire leaf to turn brown. Under the heat of the sun, the leaves of the mint plant can curl to reduce the area exposed to the sun for maximum moisture retention. Besides, the leaf edges will be burnt, dry, and brittle.

You should plant mints during a cool period such as early spring, fall, or the last frost date. If you grow mint in the summer or when the weather is hot, you need to use a cover or cover with straw and leaves to keep the plants out of the sun. If you grow mint in a pot, you can either move the pot to a shady spot or move it indoors when the afternoon sun is intense.

Lack of sunlight also causes the leaves of mint plants to turn brown mass. Mint and most other herbs need at least 6 hours in direct sunlight to grow best. Lack of sunlight will cause mint plants to lack time for metabolism and photosynthesis. From there, mint plants will not have enough energy and nutrients to maintain a healthy and green leaf state.

So, to limit this situation, you need to check the amount of sunlight that mint plants receive in a day. Place the potted plant in a place with warm sunlight in the morning and cool shade in the afternoon. If you’re growing the mint below, remove heavy branches or large shade plants so the plants can absorb enough sun.

Fungal Diseases Attack

Fungal diseases are another common cause of mint leaves turning brown. Peppermint plants can be infected with many different diseases. However, a common cause of fungal attacks on plants is a humid environment. Overwatering causes a fungus that causes root rot to attack the mint.

Mint plants will be frequently attacked by two fungi, Puccinia methane (fungal rust disease) and Cephalosporium spp (leaf blight). Some signs of fungal rust are orange, yellow, brown, and black spots on both sides of the leaves. Meanwhile, blight causes the entire leaves to turn black or brown and fall off in large numbers. This disease is uncommon and attacks mint plants that have been weakened by the rust fungus.

To prevent fungal diseases of mint plants, you need to avoid humid environments and keep the space dry. When watering, you should water at the base of the plant, not wet the leaves, especially at night. Because when you water the leaves at night, they take a long time to dry, so a humid environment creates favorable conditions for fungus to grow. You should water in the morning, then the sun will promote water evaporation and avoid the wet phenomenon.

At the same time, you should prune the old mint leaves at the bottom to avoid dense foliage. From there, you can work around air circulation issues and encourage humidity.

Pests Attack Mint Plants

The leaves of mint plants can also turn brown due to attacks by pests and insects. Worms and insects that attack mint leaves will cause mint plants to have many health problems and brown spots appear on the leaves. Some of the common insects and pests that attack mint plants include aphids, earthworms, thrips, and spider mites.


The mint leaf aphid is a small, soft-bodied insect commonly found on the underside of leaves. This insect has many different colors depending on the type of plant. Aphids will cause the mint to die and cause the mint to grow stunted. The insect will also secrete a sticky, sugary substance that encourages sooty mold growth on mint plants. To get rid of these insects, you can spray them with water until they fall to the ground. You should clean the leaves regularly both the top and bottom.


The larvae of earthworms can be difficult to detect because they are usually active at night and hide in the soil during the day. They will eat the leaves and make holes in the leaves. At the same time, the larvae of earthworms will attack mint plants, making them stunted and difficult to develop. To prevent this pest, you need to regularly check and clean the soil as well as remove old plants before planting mint.


This insect will attack the leaves of mint plants and cause them to have black spots on the leaves. Thrips are usually pale yellow or brown. To prevent thrips from attacking mint plants, you should not plant them next to plants like onions because thrips love this plant.

Spider Mites

This insect will cause mint leaves to have yellow or bronze stripes. This small spider is best spotted only when viewed with a magnifying glass. They will attack the entire leaves of the mint plant and cause them to turn yellow, brown, and fall off in large numbers. To prevent spider mites, regularly dust around the mint and clean both sides of the leaves. You can also use insecticidal soap if there are too many spiders. Do not use too many chemical insecticides because they can kill even beneficial insects for mint plants.

Roots Of Mint Will Shrink

If you grow mint in a container, as the plant grows, there may not be enough soil for the mint plants to grow, so their roots will shrink or rise to the surface. This will prevent the root system from being able to dig deep into the soil to absorb the nutrients it needs from the soil. From there, the leaves of the mint plant will turn brown or yellow.

To remedy the condition that the roots of mint plants do not have enough space in the soil, you should transfer them to a larger pot. Make sure you provide enough soil for the entire mint plant so that its root system is completely underground.

Mint root shrinkage can also occur when you plant them with other plants that are too close. Plant roots can intertwine with other plant roots, causing the plant to suffocate. Therefore, you should keep enough distance between mint plants and other plants in the garden. However, mint plants can also invade other plants if they are in a period of vigorous growth and development.

The Mint Plant Is Old And Has Lost Its Leaves

Mint is a perennial plant, so it will continue to grow every year for a few years. However, if the temperature is too low in winter, the plant will stop working. So mint leaves will turn brown or fall off in mass before they respawn when the temperature returns to warm. So you don’t need to worry about this situation, the mint plant will revive itself and thrive in the growing season.

Lack Of Essential Nutrients

Nutrients and essential substances are the source of energy that helps the leaves of mint to remain green. However, if the mint plant lacks nutrients, especially nitrogen, the leaves will turn brown. This will prevent the roots from being able to absorb enough nutrients in the soil and nourish the plants. Even when nutrients are adequate in the soil, but lack of nitrogen will prevent the absorption of plants. To prevent nitrogen deficiency in the soil, you should add compost or some kind of organic fertilizer like seaweed or organic fertilizers.

Excessive Fertilizing

As you know, nitrogen is one of the important nutrients to help maintain the leaves of mint green. However, if you apply too much fertilizer, the mint plant will also be overstressed and cause the leaves to turn brown mass. If you prefer to use synthetic fertilizers, you should use them according to the dosage recommendations from the manufacturer to avoid over-fertilizing. Too much fertilizer will cause root burn, nutrient deficiency, and leaf burn.

Even when you use organic fertilizers, too much fertilizer will cause the foliage to overgrow. At that time, the root system will not be able to provide the necessary energy and nutrients, which will cause the leaves of the mint plant to turn brown. Therefore, you should apply organic fertilizer once a month after the mint plant has matured and is 4 to 6 inches tall.

Excess Salt Accumulation In The Soil

The excess salt build-up in the soil also causes the leaves of mint plants to turn brown. If you regularly water plants with tap water, you should pay attention to this cause. Tap water may contain salts such as sodium and magnesium. These substances tend to accumulate over time in the soil. In addition, fertilizing will also contribute to the introduction of salt into the soil.

When excess salt accumulates in the soil, the plant’s root system will not be able to absorb moisture and nutrients. From there, plants will lead to dehydration and withering.

To remedy this situation, you should flush excess salt out of the soil every few months. You simply use pure water such as rain or distilled water and drench the soil until the water comes out of the drainage holes. From there, the excess salt will also be removed by the water flowing out to the soil.

Can I Eat Brown Mint Leaves?

If mint leaves are picked and stored properly, you can eat them. However, if mint leaves turn brown while on the plant and yellow spots appear, you should not eat them. The reason is that they may have been infected with fungal diseases or pests.

You also shouldn’t eat mint leaves after they’ve been sprayed with fungicides or pests. Because toxic substances are still present on the leaves, it is not safe to eat, especially raw and unprocessed. You can also eat spotted mint leaves, however, these are spots caused by leaf-eating insects, not spots caused by fungal diseases.


Mint leaves can turn brown for a variety of reasons. Some of the underlying causes are improper watering, too much or too little light, lack of nutrients, over-fertilizing, or pest attacks. In addition, the phenomenon of old leaves can also cause leaves to turn brown mass.

To avoid this phenomenon, you need to water according to the actual user needs of the plants. Place the pot in an area that receives at least 6 hours of direct sunlight daily and fertilize once a month during the growing season. In addition, you also need to regularly check and clean the sides of the leaves to remove harmful bacteria and fungi.

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