Why Are My Mint Leaves Turning Brown? (And How to Fix It)


Indoor potted mint plant leaves turning brown.

Mint is a plant known for its flourishing ability as it is easy to grow and thrives in shady environments.

However, you may stumble upon a problem as you see browning in your minty oasis.

The earlier you combat this, the better chance that you have of saving your plant paradise.

Mint leaves turning brown due to low humidity, improper watering, and diseases such as fungal infections. The less likely reasons could be nutrient deficiencies, heat scorching, limited roots, or aging. To fix this try keeping your plant lightly misted through a humidifier, water it consistently, and use a fungicide to avoid these issues for the future.

Causes of Mint Leaves Turning Brown and Solutions

It can be difficult to guess what problem is causing the browning in your mint plant. You should always be observant of your plants to take note of any changes in their composition. 

A good caretaker would spot the browning issue early on by regularly checking on the health of their plants.

Improper Watering

Watering can be a challenging task when you have a plant that you’re unfamiliar with.

Improper watering consists of two branches: overwatering and underwatering. Too much or too little water can affect the tissues that make up the plant.

The tissues and cells that create the structure of what a plant is, holds water to supply the plant with nutrients. In order for your mint to thrive, you have to find the “sweet spot” for its water supply.

Similarly, to humans, plants need to breathe. When too much water is in the soil, it removes the oxygen needed to “breathe” properly. 

Overwatering causes the plant to drown. If your mint can’t receive enough oxygen to create nutrients for itself, it will die.

Underwatering deprives the mint of getting enough moisture to properly supply life to itself.

Lack of water will cause the plant to try and preserve itself by keeping the stem healthy. This can create browning in the leaves as well.

How to Fix

Be consistent with watering and give it the same amount every time. You want to create an environment for your mint that it can thrive in. 

Create a watering schedule and keep track of how much water you’re giving your mint plant. Mint is best off watered 1-2 times a week at most. 

The watering schedule depends on the climate and the humidity of your area. You’re best off moistening the soil but not drenching it. 

If you have holes at the bottom of your planter, stop watering as soon as you see water to trickle out of the bottom holes.

Inadequate Humidity

Keeping a plant in a moderately humid environment is extremely important. Every plant needs a different level of moisture in the air to thrive.

Humid conditions allow the plant to stay moist in a way that isn’t related to the roots of the plant.

Dry, stifling air will shrivel up your mint and dry up the leaves to become brown.

If you live in a dry climate or if it is a winter month, you may want to consider this to be your problem. Winter air can be drying to your plant, even if it’s inside.

You may notice a drooping, brown mess on the edges of the leaves. Soon after, the entire leaf will turn into a yellowing/brown color.

How to Fix

Invest in a humidifier for your plant. Humidifiers keep the air moist regardless of the climate or natural moisture in the air.

Try getting a misting bottle and turning it to the “fine mist” setting. Do not let the water collect on the leaves or it will start to attract pests and fungus which will cause more browning.

Also, try localized humidity! Localized humidity is when you keep plants close together so their expelled humidity can be shared with the surrounding plants. 

This is the most natural and controlled way to create a humid environment for your mint and other plants.

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Heat and Sun

Although most plants enjoy direct sunlight, mint plants always prefer shady areas to grow in. The shade allows it to spread quickly and thrive.

If you’re keeping your mint in direct sunlight, stop! It does not need direct sunlight to thrive as it grows.

Placing it in an area where sunlight hits it straight on is not beneficial for your mint.

Scorching, the act of sunlight burning the plant, can take place when your mint is placed into those conditions.

Temperature can also affect your mint. If where you’re keeping the plant is particularly hot, a similar browning issue may arise.

How to Fix

Keep your mint in a cool and shady area! Don’t allow for your plant to receive direct and overhead sunlight or it will begin to burn and brown itself.

If you’re an indoor mint caretaker, you want to keep your mint in a shaded corner of a brightly lit room.

Create filtered light with thin curtains to prevent too much sun from affecting your mint.

If temperature is your issue, evaluate where you keep your mint. Do you place it near the heating or A/C source? If so, move it ASAP! 

Never place your plants somewhere to be directly affected by temperature regulating systems such as a heater. Keep your mint in a moderately temperate room.

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Constricted Roots

Constricted roots are when a root system begins to grow back on itself. So it is important to know how deep do mint roots go?

This happens when a plant’s root outgrows the area that it’s living in because of the lack of space.

Mints that you grow indoors suffer from this most often because of the restricted growing space in a planting pot. 

Outdoor plants have all of the soil in the world (quite literally) to spread itself throughout. Planter pots only have so much space inside for the root system to grow into.

Constricted roots aren’t able to get sufficient amounts of water because of the root system “strangling” itself in a strange way. 

As the roots grow and run out of space, they have to try and circle themselves around the pot they grow in.

At times, the roots may tangle, create knots, or tightly crossed patterns. All of these variations result in the roots having their flow constricted and sometimes cut off. 

This prevents them from grabbing water and nutrients present in the soil to keep the plant alive. Thus, the leaves may begin to brown.

How to Fix

There are a few routes you as a caretaker can do to aid this issue before it’s too late.

Try untangling the root system gently and carefully.

You don’t want to create any damage to the roots because it is the most important part of the plant that is needed for survival. If you end up damaging it, it is irreversible.

After you untangle the roots, you can replant in fresh soil and a larger pot to prevent the same issue from occurring again.

Give your mint plenty of room to grow and flourish by doubling the pot size from before.

Also, try separating the mint clusters into two separate pots after you carefully untangle the root system.

Because mint spreads quickly, you may find an entire bushel in one planters pot. 

Counteract this by splitting the bushel into as many smaller pieces as you can and placing them into smaller pots!

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Natural Aging

Plants are just like every other living thing in the world in which they have a beginning and an end.

You may find that the browning of your mints is purely from natural aging and not from other issues such as disease or improper watering.

All plants have a life cycle and more specifically, so do parts of them.

If the leaves near the bottom of your mint plant (closest to the soil) are browning, you should assume that natural aging is the perpetrator.

New buds and leaves occur toward the middle and top of plants.

If your mint plant is growing older, it will always try to preserve the most youthful parts of itself first such as the new buds. 

The leaves closest to the soil will begin to turn a dark yellow and grow into a brown color prior to falling off of the stem.

Don’t be alarmed! This is a natural part of the process and you should use your best judgment to confirm that your mint leaves are going through that process. 

How to Fix

Although the mint leaves may be turning brown, they might not fall off quickly because the process takes some time.

You can aid your plant in this part of the plant cycle through careful pruning.

Pruning is beneficial not only for ridding of brown parts of a plant but also for creating bushier and fuller plants in general. 

The quicker you get rid of the pesky aging, the quicker you’ll see the newer parts of your plant flourish!

Here are a few tips for pruning!

  • Only prune when your plant is healthy. Pruning during any other time may shock the plant and kill it.
  • Cut at a diagonal so you don’t damage the area and prevent growth.
  • Take your time! You don’t want to do this in a haste and make a mistake! Plant damage is irreversible more often than not.

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Diseases

Mint, as well as other plants, are susceptible to disease at any time. Mint specifically is prone to fungal issues because of its enjoyment of shady areas where it can collect moisture.

Mint rust fungus infects mint plants on a regular basis. Fungus occurs when water sits on the plant for extended periods of time. 

Because mint enjoys shady areas, it is the perfect storm for fungus to grow and cause browning on your mint leaves!

How to Fix

Fungus releases spores which make it an extremely contagious disease. Because of this, you will have to discard the infected plant completely and tie it in a plastic bag to prevent it from releasing spores that may attack adjacent plants.

If the fungus occurs early on, you can try to cut off the parts of the plant that are infected, but you have to do that at your own risk.

You can slow the fungal process by changing the way you water the mint plant. You want to give the least amount of water to it that you can without depriving it of moisture. 

If you give your mint even the slightest bit too much, you will only encourage the fungus to thrive.

So, if you are able to catch it early on, remove the plant from the pot and give it fresh soil and a fresh planting pot. 

Now, if you want to reuse the planting pot that the mint was once in, you have to sanitize it properly to rid the pot of fungus.

Soak the pot in a bleach solution in a 1-part bleach to the two-part water cleaning solution.

Scrub the pot and rinse thoroughly before planting anything else in there.

Source: Plantvillage; Penn State University

Nutrient Deficiency

Mint leaf tips turning brown due to nutrient deficiency.

Plants often go through nutrient deficiencies if they aren’t getting the proper amounts of minerals from the soil.

Your mint may minimize itself to stay alive with the nutrients that are available to it.

Your mint plant needs phosphorus, calcium, potassium, and nitrogen in the soil to provide enough sustenance to keep it healthy and prevent the browning that may occur.

A nutrient deficient mint plant will kill off older parts of the plant to keep the younger buds alive.

Plants will begin to brown and die off if the soil is completely reaped of its minerals.

How to Fix

The best way to fix this issue is to supply good fertilizer or create compost. Composting is a guaranteed way to supply nutrients to the roots in an organic way. 

You can use natural kitchen ingredients like fruit and vegetable scraps, coffee powder, etc.

If you do decide to fertilize, do not over-fertilize or you can cause fertilizer burn which will also create browning and issues.

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Salts Buildup

Salts are minerals that may be present in the soil after fertilization or use of tap water.

The minerals that provide plants with nutrients from fertilizer can leave a salt residue in soil afterward if improperly fertilized.

Excessive salts such as sodium and magnesium can damage mint plants through the root system.

The salt residue can build up and prevent the soil from dispersing water properly. 

Salts also cause the roots to be unable to properly suck the water up and supply it to the plant.

The inability to get water throughout the system can cause browning throughout the mint leaves.

How to Fix

Switch to purified water that does not contain such a high mineral content to destroy the plant.

Tap water can be detrimental to a sensitive plant such as variations of mint. Fertilizers are high in minerals and salts so avoid excessive use.

Over Fertilization

In an effort to give your plant extra nutrients, you may have done the counter effect and damaged your mint instead.

Fertilizer contains super strength minerals that your plant needs such as nitrogen and potassium.

If you provide enormous amounts of these minerals, it can block the ability for roots to absorb moisture through the root system. 

So, when you over-fertilize, you run the risk of fertilizer burn. This causes browning and yellowing around the edge of the leaf if not the entire leaf.

How To Fix

Avoid using too much fertilizer by cutting back on regular use. Try using fertilizer every 1-3 months to keep the health of the root system intact and healthy.

Another alternative is to purchase a soil with fertilizer already in it to prevent putting too much at once.

If you want to provide nutrients to your mint, composting (as mentioned above), is a great alternative and the healthiest way to give your mint what it needs to succeed.

Insect Infestation

Insect Infestations are common amongst all plants, even mint. Insects such as spider mites are the cause of browning in foliage.

Spider mites enjoy warm conditions and create brown and yellow coloring on the leaves.

These pests could be the source of your problems if you keep your indoor mint in a warm and damp environment that they can thrive in.

How to Fix

The best way to get rid of pests is to change the environment of the plant. Move the mints to a cooler area so spider mites don’t have their desired temperatures. 

If your mint is in a humid location or if you mist with water regularly, hold back on extra moisture so that the spider mites die off.

Source: Plantvillage; Penn State University

Cold Drafts

Plants such as mint don’t thrive in freezing weather. Houseplants cannot stand drafts because it imitates winter-like conditions in which plants begin to preserve themselves. 

When mint is placed in a drafty area, directly in front of a window, or by an air conditioner, it causes the plant to go into shock.

A sudden shock like that will not only cause browning issues but may kill your mint off altogether.

How to Fix

Place your mint in a moderately temperate area. Avoid draft rooms and corners, as well as window sills.

If you can, aim to keep your mint in a room between 60-80°F (15-27°C). This will end the browning from cold shock and keep your mint healthy.

Maintain this temperature at all times to prevent the plant from dying unexpectedly.

Summary

ProblemSolution 
Nutrient DeficiencyFertilizer
Compost
DiseasesDiscard PlantTrim Off Infected Parts
Natural AgingPruning
Heat and SunIndirect Sunlight
Moderate Temperatures
Poor HumidityPurchase HumidifierLight misting
Constricted RootsUntangle RootsReplanting
Improper WateringCreate Watering Schedule (1-2 times a week)Water with Consistent Amount of Liquid
Salt ResidueSwitch to Filtered WaterDon’t over-fertilize! Only once every 1-3 months 
Over FertilizationOnly fertilize once every 1-3 months or use a soil that contains natural fertilizer
Insect InfestationAvoid keeping your mint in a hot and moist location
Cold DraftsKeep the temperature between 60-80 degrees at all timeGet rid of drafts by changing the location

Growing beautiful plants can be a challenging task, but don’t give up! Mint is one of the easiest things to grow.

Smooth over the bumps in the road and keep riding on your way to plant paradise! 

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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