Last Updated on June 9, 2022 by Admin
Mint leaves turning brown is something no plant owner ever wants to see.
Of course, you don’t want to use these brown leaves for cooking or garnishing your food. But more importantly, browning is a sign that something is happening to your plant.
As such, while mint herbs are easy to care for and grow in your herb garden, any time you see brown leaves develop warrants further investigation.
Why are my mint leaves turning brown? Common causes include low humidity, watering problems and diseases.
Other reasons for brown leaves on mint include excess light, natural aging and nutrient deficiencies.
As such, it is important to check each of these potential issues, then treat the plant and finally adjust your care routine to prevent this from happening again.
Mint Leaves Turning Brown Causes and Solutions
There are a few possible causes for mint leaves turning brown. As such, it is important to go through each one and eliminate them before narrowing down the culprit.
Avoid just guessing since it can make you apply a different treatment that may not work to solve the problem.
Once you have more experience and if you regularly observe the details of your plant, you’ll be able to quickly diagnose problems.
Fungal Diseases
Fungal diseases are common issues with mint plants because of there preference for shady locations.
While keeping them in a shaded spot outdoors lets them grow, it also increases the chance of water collecting on the soil or on the plant.
When this happens, it increases the possibility of fungal growth.
Fungal diseases can cause mint leaves to turn brown. Although, this depends on the kind of fungi that infects it.
Fungi will grow, develop and thrive in damp conditions. And the lack of light prevents the moisture from quickly drying up.
In most cases, mint is grown outdoors.
So, people tend to leave in a more shaded area to grow.
Indoors, this is usually less of problem especially if you keep the herb in medium to bright indirect light.
Nevertheless, excess moisture can still occur if you overwatering the plant to wet the leaves excessively when you water the plant.
Solution
Fungi are very contagious because they spread via spores. Once these spores are released by the fungus into the air, they can transfer to other plants easily.
Thus, isolating any infected plant is important.
Otherwise, you may soon be dealing with many plants with the same fungal disease.
I’ve also seen some gardeners just cover the infected plant with plastic, then discard it to prevent the fungal disease from spreading to the rest of his garden.
However, if you catch the problem early, you can deal with it by cutting down on water which will limit the fungi’s ability to grow and spread.
Pruning away any affected leaves is also needed.
If you want a faster solution, you can repot the plant in fresh soil.
But you need to be careful to remove all the soil from the roots and discard them. Make sure to sanitize the pot before reusing it.
You can use a hydrogen peroxide solution or a bleach solution to clean the pot.
Watering Issues
As mentioned, watering issues is one of the main causes of mint leaves turning brown. However, its negative effects are not limited to fungal diseases.
When it comes to problems regarding watering plants, it will always come down to 2 things.
- Overwatering
- Underwatering
And that is the case here.
Neither is good for the plant. Although, as it often the case, overwatering is more dangerous.
That said, you want to stay in the middle since this will allow the plant’s roots to get enough moisture while being able to breathe as well.
Water is important for mint to survive since it needs moisture to stay healthy.
Also, water is the mode of transporting nutrients from the soil to different parts of the plant.
So, when there isn’t enough nutrients and water getting to the leaves, you’ll see mint leaves turn brown,
As such, underwatering can eventually dry and damage the roots due to dehydration.
But before that happens, the lack of water will cause the plant to fight for survival.
When this happens, it will cut down on less essential functions and focus on self-preservation. As such, the roots and stems will try to stay healthy as long as they can at the expense of the leaves.
So, your see mint leaves turning brown.
Overwatering is usually more harmful for plants because it has the capability to drowning the roots.
When there’s too much moisture in the soil, it pushes out most or all of the oxygen from the air pockets. In doing so, this suffocates the roots.
Short-term suffocation affects overall plant growth and function.
But if the excess water in the soil does not drain or dry fast enough, the roots can die from suffocation due to lack of oxygen. After they die, they rot.
Dead and rotten roots never get revived. They also stop functioning.
As a result, you end up with an underwatered mint plant that’s also malnourished since there are fewer roots to absorb water and nutrients from the soil.
This is regardless of how much you water the soil or fertilize it.
Thus, you end up with mint leaves turning brown as well.
Solution
Mint likes consistently moist soil. But it does not like drying out nor does it like staying in wet soil either.
So, it is important to find the perfect balance.
To do so, there are two things you should try to achieve, consistency and knowing when to water the plant.
Mint like being watered 1 to 2 times a week.
Although, how often will depend on the climate condition that’s currently prevailing.
Hotter temperatures during the summer coupled with more sunshine speeds up the soil drying process. But the colder temperature with less sunlight during winters slows it down considerably.
So, adjust accordingly.
Avoid letting the soil stay wet. Also, don’t let the soil completely go dry.
Also, make sure to use a pot with drainage holes to avoid waterlogged soil.
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Low Humidity
Mint need humidity. This gives the plant the moisture it needs.
Note that the moisture in the air that causes humidity it related but not the same as water in the soil.
As such, the soil can be overwatered while the plant may still lack humidity.
That said, a well-hydrated plant can tolerate low humidity better. But the moisture in the soil does not replace the plant’s need for humidity.
In the case of mint, dry air will cause its leaves to turn brown.
However, you’ll notice that the browning happens in the edges and tips of the leaves.
If the low humidity persists, you’ll eventually see the browning spread and then cover entire leaves. In many cases, you’ll see a yellowish-brown leaf color as a result.
In addition to mint leaves turning brown, lack of humidity will make the leaves shrivel and dry up. You’ll see the tips and edges get crispy and brittle as well.
Also, the plant will droop later on.
Solution
Mint like humid environments. Try to keep humidity at 45% and above as much as possible.
If you can go higher, the plant will be happier.
The most important thing is to avoid insufficient humidity.
Dry air will cause all the negative effects mentioned above.
And when you see this begin to happen, it is important to help out the plant.
You can set up a humidifier, mist the plant or use a pebble tray to help increase humidity around the plant.
Keep in mind that brown leaves will never turn green again.
So, any damage from the dryness or lack of humidity is permanent. And you’ll have the prune the entire leaf or section of the leaf that has been affected.
Too Much Direct Sunlight
Most plants thrive in plenty of light.
And to a degree, mint does too. But you need to be careful with too much light exposure since this can damage the leaves.
Outdoors, mint thrives in partially shaded areas. Keep it away from full sun or strong and long exposure to the sun’s rays.
Instead, place it somewhere that has shade for optimal growth.
Indoors, the plant will do best in medium to bright indirect or filtered light.
Again, avoid direct sunlight.
Keeping the plant in direct sunlight can damage its leaves. And with too much exposure to the sun’s rays on a daily basis you’ll see the mint leaves turn brown.
This is a result of scorching, where the leaves of the plant get burned by the intensity of the sun’s rays.
It is also important to be aware that grow lights can likewise do the same to the plant.
Since grow lights don’t provide the same color spectrum as the sun does, plants need more artificial light exposure.
Thus, the longer hours increase the intensity of the heat coming from bulbs.
This means that if you place the plant too near the bulbs, you may end up with brown leaves on mint plant. At times, they may turn black and look like burn marks as well.
Solution
Keep mint is a cool area with not direct sunlight exposure.
The simplest way to do this is to check the plant at different times of the day to ensure that the sun’s yellow rays never touch its leaves.
By doing so, you avoid scorching or burning.
This will prevent you from seeing your mint leaves turning brown.
Aging
Like all living things, mint will naturally age. And as it grows older, you’ll see some of its growth patterns change.
One is mint leaves turning brown.
Unlike the other causes in our list, this one is natural and part of the plant’s life cycle. And like humans, aging is the culprit.
The one distinctive feature of the browning of the leaves in mint due to aging is where it happens.
In this case, you’ll see the lower leaves turn brown.
These are the older leaves. And the younger, newer leaves are those in the middle and top part of the plant.
Like all living beings, you try to preserve the young.
As such, the younger leaves will receive more attention when it comes to growth, development and energy as the plant gets older.
The bottom leaves usually turn yellow, then a darker shade of yellow. After that, they transition to brown before they start falling off.
While leaf drop never looks good, this is something you should not worry about.
Instead, it is just a sign of the normal plant life cycle.
However, the tricky part here is to diagnose this properly.
If you happen to guess that it is aging but the actual cause is something like overwatering, then the plant will sustain more damage because you end up not doing anything.
Solution
In general, you don’t have to do anything as the brown leaves will eventually fall off.
However, seeing brown foliage on any plant is never visually appealing.
Also, if the leaves happen to drop on the table, ground or soil, it is important to remove them and discard them.
Keep in mind that these leaves will decay. And if you leave them around, they’ll attract pests and diseases.
So, always make sure to clean after your plant.
Similarly, pruning is a good way to quickly remove the brown leaves in mint plants.
Doing so allows the plant to stop using any resources or energy to support these old leaves. Instead, it will be able to redirect the energy to the younger leaves and push out new foliage as well.
Pruning also encourages mint to grow more which helps it become bushier.
