The fresh, vibrant green mint is used for a variety of purposes. Let us look at the possible causes for mint leaves to turn brown and the solutions that you can implement.
#1) Improper watering and poor drainage
Every plant has different watering needs, and it can be a task to keep track of the amount of water you give to your plants.
Improper watering would mean either of the two issues: underwatering or overwatering. Too little or too much water can affect the plant tissues.
Plants need water to live. Underwatering the plant means that the plant is not getting enough moisture to sustain itself.
Lack of water will have your mint trying to preserve itself by trying to keep the stem nourished, which can cause the leaves to become brown, as the plant does not have enough energy to provide for the entire plant.
Sometimes, people overcompensate by watering their plants too much. This is also not good for the plants. The roots of the plant need oxygen to breathe.
If there is too much water in the soil, there is no space for proper air circulation under the soil. The roots need oxygen in order to procure the nutrients necessary to live.
Overwatering causes the plant to drown, flushing out the nutrients it needs to survive. Sometimes, the container can also be a problem, if it does not have a good drainage system.
Similarly, you might be watering correctly, but the soil you have used could be too compact for the water to drain.
An overwatered mint will have brown spots on the inner leaves or near the stem.
Be consistent with the amount of water you are providing to your mint. Most of the time, mint needs to be watered 2 to 3 days a week. If you notice your container dripping while you are watering it, you are overwatering.
If the soil is the problem, consider repotting the plant in a potting mix with compost so as to get good drainage.
Plant your mint in a container with good drainage. If your pot does not have any drainage, you can drill two holes at the bottom so that excess water can flow out.
#2) Inadequate humidity
Every plant needs different levels of humidity to thrive. A moderately humid environment is very important for mint.
Humid conditions help plants with moisture that does not come from the soil.
Very dry air can cause your mint to shrivel up and turn brown.
Even during the winters or in a cold and dry climate, the mint can dry up even inside the house.
The edges of the leaves will turn brown and soon after, the entire leaves will become brown or yellow.
If you have no scope to introduce your plant to any humidity in the air, you can invest in humidifiers for your plant. Humidifiers keep the air humid, no matter what the natural climate is.
You can get a misting bottle. Turn it to the “fine mist” settings. Make sure no dampness collects on the leaves of the mint, as it will attract viral and fungal infections, causing even more browning.
Another method you can use is localized humidity. Localized humidity is when plants are kept close together so that the expelled moisture from the plants is shared by all the other plants.
This is the most natural way to make sure that your mint gets the humidity it requires.
#3) Heat and sunburns
While most herbs need plenty of sunlight, mint needs a shaded place to grow. It does require the sun, however, exposure to direct sunlight can cause the mint leaves to be scorched.
Excess heat can cause sunburns and brown and wilted spots on the mint leaves.
A lot of time, too much sun can dry up the roots, stressing the plant and thus turning the leaves brown.
Not only scorching sunlight, but the high temperature in any form can impact the mint in a negative way.
If the place you are placing the mint in is particularly hot, it is going to burn and turn brown.
Ideally, keep your mint in a place where it will receive morning sunlight and partial shade throughout the day.
You can keep your mint in a shaded part of a sunny room.
Always keep your mint in a moderately temperate area. Do not keep it too close near a hot source like a heater or someplace where it will get direct sunlight. Do not keep it too close near a cold source like an AC or a completely dark space without any light.
#4) Cold drafts
Just as mint does not do well with direct sunlight, it will also not survive in cold, freezing weather.
Most houseplants cannot stand cold drafts because it creates an illusion of the onset of winters, during which time the plants turn brown to preserve themselves.
If mint is placed in a drafty area, like directly in front of a window, or near an air conditioner, the plant will go into shock.
This shock not only causes the leaves to turn brown, but it can also kill off your mint.
Place your plant in a moderately temperate area. Avoid cold corners, draft rooms or window sills.
Try to keep the temperature of the room between 60-80°F (15-27°C). This will help your mint from going into shock and turning brown or worse, dying.
#5) Dormant stage
During the cold months, your mint could become dormant, especially if you live in a region that gets frost.
The leaves will turn brown and fall off and die, just leaving the stems. This is what plants do to self-preserve.
Cut the stems back to a few inches above the ground and water them well. When the weather turns warm again, the mint will re-grow.
#6) Nutrient deficiency
Plants absorb the nutrients present in the soil in order to survive and live. Mint needs phosphorous, nitrogen, potassium, and calcium to provide it with the sustenance it needs to stay healthy.
If the mint does not get the required amount of nutrients, it goes through a nutrient deficiency. In such cases, the plant minimizes itself in order to stay alive with the nutrients available to it.
A nutrient deficient plant will kill off the older parts of the plant in order to provide nutrients to the newer growth. As a result, parts of the plant will become brown and eventually die.
The best remedy for a nutrient-deficit plant is to use a good fertilizer or compost. Compost supplies nutrients to the soil organically.
Ensure that you do not overfertilize the plant, as it could also lead to fertilizer burns which would also cause the leaves to turn brown.
Overwatering also strips the soil of its nutrients. Make sure you water the plant as required.
#7) Fungal diseases
Mint likes shaded places, which is why it can be especially susceptible to moisture which is one of the main causes of fungal diseases.
Mint plants are prone to mint rust, which develops when water or moisture sits on the plant for prolonged periods of time.
Web blight is another fungal disease that troubles the mint plant. These fungal diseases can cause the mint to become brown.
Fungal diseases are extremely contagious, so make sure that you isolate the plant from any other plants.
If the fungus is in the earlier stages, you can remove the affected parts and dispose of them.
If it is in the later stages, the best thing to do is to discard the plant completely and avoid reusing the soil and the container it was planted in.
#8) Pest infestation
Some pests that trouble the mint plant can leave brown spots all over the mint plant. Mites, aphids, and thrips are especially harmful to mint.
These pests suck the juices out of the mint leaves, leaving behind brown spots all over.
A lot of plant-friendly insecticides are available in the market that kills off the pests without harming the plant.
Sometimes, spraying the leaves with a jet of streaming water can also rid the plant of all the pests.
Introducing beneficial bugs that feed on these pests can also work.
#9) Build-up of salts
Salts can accumulate in the soil after the use of fertilizers, or if you use tap water.
If you do not fertilize the plants properly, the minerals that provide nutrients to the plants can leave behind a salt residue.
Excessive salts like sodium or magnesium can damage mint plants by ruining the roots. If the residue builds up in the soil, it can prevent the soil from evenly distributing the water.
Salts can also prevent the roots from absorbing the water and supplying it to other parts.
If the tips of your mint leaves turn brown and crispy, there might be a salt build-up in your soil.
Switch to purified water that does not contain a high level of minerals that could destroy the plant. Tap water could be harmful to sensitive plants like mint.
Do not use fertilizers in excess and use good quality fertilizers.
If you can see white crystals on your soil, try to dissolve them by pouring distilled water over the soil.
You might sometimes feel the need to provide your plant with some extra fertilizer to give it extra nutrients.
However, it could have the opposite effect and end up destroying your mint plant.
Fertilizers contain nutrients that mint needs like nitrogen and potassium in concentrated quantities.
If you provide your plant with a lot of fertilizer, it can prevent the roots from absorbing any moisture.
Similarly, over-fertilization also leads to a risk of fertilizer burn. This can cause the leaves to turn brown and yellow around the edge of the leaf and gradually affect the entire leaf.
Do not use fertilizers in excess. Try using a fertilizer every 1 to 3 months so that the roots of your plant remain healthy.
An alternative is to use soil that already has fertilizers mixed in it so that you do not need to add in too much at once.
Another option is to use compost instead. It is organic and the healthiest alternative to provide your mint with the required nutrients.
#11) Constricted roots
Mint is a fast spreader. This means that mint spreads its roots very fast and invades the space of all other plants. This is why mint is best grown in containers.
But the problem with this is that with limited space, the roots grow back on themselves, choking themselves.
This can prevent the roots from properly absorbing nutrients and supplying them to the other parts of the plant, resulting in leaves turning brown.
Try to gently untangle the roots.
Replant the mint in a bigger pot so that your mint has plenty of room to grow.
#12) Natural aging
Just like other living beings, plants too grow and eventually die. Sometimes, there is no other issue for the browning of your leaves but the fact that your plant has grown old and is dying.
If the leaves at the bottom of your plant are browning first, it is most likely happening due to aging.
As plants grow older, they try to preserve the newer growth while slowly removing attention from the older parts. This is a natural life cycle and nothing to worry about.
While there is nothing you can do about your plant dying from old age, you can help prolong its life a bit. the leaves do not fall off as soon as they turn brown. The process takes time.
As you see the leaves turning brown, prune them off. This not only gets rid of the browning parts but also creates a better and bushier plant, giving way for more new growth.