Mint Leaves Turning Brown – 3 Reasons with Remedies

Introduction

The flavor of mint is one of the popular ones in many food menus. It’s great to have a few mint leaves in your many anytime. 

But not if the mint leaves are turning brown. 

What we mean is, brown mint leaves might indicate a number of things that are going wrong with the plants, including fungal attacks, poor irrigation, etc. 

In today’s article, we’ll talk about three reasons behind brown mint leaves, and the handy solutions to each. 

Are Mint Leaves Turning Brown Bad?

As it’s suspected, brown mint problems might be caused for a number of reasons. And before deciding if you can add the affected mint leaves to your food menu, you get to understand those reasons first. 

For now, let’s just say that if the brown mint leaves are because of fungal attacks, you can’t eat them anyway, neither can keep them near the plants. 

If it’s because of watering or humidity reasons, you can undo the brown effects of the leaves and turn them green. Leaves that are cured in these ways, can be taken in your food or with tea/coffee. 

Types of Brown Mint Problems

Although many people look at all of the ‘brown mint’ problems in the same way. But let us tell you- different combinations, positions, and level of brown-yellow mint leaves indicate different reasons.

Here are a number of possible causes- 

• Brown spots on the underside and yellow splotch on the top. 
• Inner leaves are rotting(brown) and the outer ones are fine.
• Mint Tips Are Getting Brown.

Case 1: Brown Spots on Underside and Yellow Splotch on Top

Source: Helpfulgardener.com

In this case scenario, your mint leaves have got black or brown spots on the underside, along with yellow dots, splotches on the top part. This is more likely to happen in early spring. 

On top of that, these symptoms might have progressed into turning leaves completely brown and eventually, dropping them off. 

When it’s late in the summer or early fall, there will be a re-growth of these dropped leaves. But they will still contain dark/brown spots in them. 

Reason: Mint Rust Fungus 

If you’ve found similarities to the aforementioned symptoms, your mint plant is probably suffering from a fungal invasion called Min Rust Fungus.

It’s also called Puccinia menthae, which attacks none other than mints like peppermint, spearmint, etc. 

Why on earth this would happen? 

Well, the #1 reason for this fungus is excess humidity around the leaves. This might happen from reason like- 

• Overhead irrigation that leaves water drops on plants.
• Closely planted mints. 
• Closed and humid environment around the plants.  

As a matter of fact, humidity(or water drops) helps this fungus to germinate and increase in number. 

How to Prevent Mint Rust Fungus? 

Step 1: Separate The Affected Leaves

If the disease is at a mild stage, our first advice would be to remove the leaves that are infected. Don’t let the affected leaves be on the potting soil. Burn them out or keep them from the plants anyway. 

Step 2: Ensure Better Air Circulation

If you think the plants are too congested to develop some humidity among the leaves, it’s time to free up some space. And the first way to do that is by trimming the mint pants.

Here is a nice video guide on how to trim mint plants.  

Also, plants that are on pots should be brought away from walls or corners. That will boost the air circulation around leaves. 

Step 3: Change the Way of Watering

Water drops stocked on the leaves cause this fungal disease. Therefore, start watering the plants on the bottom instead of on the top. 

Also, water the plants when it’s morning. This will give some time to evaporate the waters. 

Step 4: Apply Fungicide

If the invasion is serious enough, and none of the 3 steps above work right, it’s time to apply some fungicide on the meant plants. 

The best fungicide to apply is Azoxystrobin. This fungicide is likely to undo the chemical effects on the plants and let you harvest(collect the leaves) quickly. 

Here are some recommended Azoxystrobin for mints- 

• QUALLI-PRO Strobe T Fungicide 128oz
• Syngenta Mural Fungicide 1#

Mints that are ornamental, can be treated with chlorothalonil. This has a longer-lasting impact. But that won’t bother you as the mints are ornamental. 

Here is a chlorothalonil fungicide for mints- 

• Ortho MAX Garden Disease Control Concentrate

Also, apart from doing all 4 of the steps above, don’t forget to disinfect the plant container(pot) on a regular basis. This will prevent further fungal attacks. 

Case 2: Inner leaves are rotting(brown) while outer ones are fine

This is another common case where the top layer of leaves look to be good with some new growth. But beneath that, the inner leaves are rotting and turning brown. 

Along with that, another symptom that often teams up is- roots winding around the rootball. You can also see some of the roots poking out of the drainage hole of the pot. 

Reason: Overwatering and Aggressive Growth 

You might have heard that mint plants need to be watered regularly. But if you overdo that, it will create problems like browned leaves on the bottom layer along with overgrown roots. 

By overwatering, we mean to water the plants once every 1-2 days even when it’s not summer. 

As mints are quite aggressive in terms of plants, when you will find the leaves full and nice, you have to suspect an overgrown root anyway. 

Note: The tips to identify if it’s just a drainage problem or it’s a fungal attack, check for healthy leaves on the top. If they’re there, then it’s not a fungal issue. If not, you can go back to Case 1. 

How to Prevent Rotting(brown) Min Leaves? 

Step 1: Water Less

You will start by picking the bad leaves off. Once it’s done, start developing a habit of watering less for the plants. Especially, when it’s not summer, water doesn’t evaporate enough and surrounds the roots and plants. 

Decrease both frequency and amount of watering. You can start watering once every 3-4 days if the environment is humid enough.  

Step 2: Divide/Repot It Into A Bigger Pot

As said before, if you can poking out roots from the drainage hole, that means the roots are overgrown and you need to either divide the plant into two or repot the whole plant into a bigger container. 

Let’s talk about the first option first. 

The way to make a new mint plant from one is by taking cuttings or layering the plant into two. Both are meant to keep the plant healthy and natural. 

Moving on, if you don’t need a few mint plants, you can try moving the existing one into a bigger pot. This will let the root spread out in a proper manner. 

Case 3: Mint Tips Are Getting Brown

This case involves mint leaves that are getting brown around the tip only. And this is occurring mostly with older leaves, where the new and younger leaves are pretty fine. 

In this situation, applying fungicide or watering less won’t work mostly. Therefore, we need to identify the real reason behind it. 

Reason: Burn from Excess Heat

If the leaves are exposed to extremely hot weather(100-degree Fahrenheit or more), it can be too much. This is not necessarily to take place all day long. A couple of hours under such heat can cause some burn on the plants. 

As another consequence of this excess heat, the water will evaporate faster. And it will dry off the roots as well. 

How to Prevent Rotting(brown) Min Leaves?

Step 1: Relocate The Plants to A Colder Weather

If it’s the excess heat and sunlight that are bothering the plants, the first thing to do is to relocate it to a colder, shadier place. 

The plants will still need sunlight, right? So, make sure that the morning sun gets on the plant for a few hours. But don’t let the hot sunlight of noon be on it anyway. 

Step 2: Increase Watering Frequency 

If you move the plant into a colder place, the humidity will still be high there. Therefore, water will evaporate faster and leave the root dry. 

Therefore, we’d advise watering once/twice a day in this season. 

However, don’t increase the amount of water. It should be split into halves and dropped on the plant roots as routined.

Bottom Line

That was the end of this discussion, friends. Treated properly, brown mint leaves are not that serious of a problem for all of the mint lovers out there. However, applying any fungicide or pest control chemicals should be considered properly before you make it happen. 

FAQs