When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.
I enjoy growing herbs in my yard for cooking, and to bring fragrance to my outdoor space. One herb I have always struggled with, though, is mint. Its prone to a wide range of issues, including mint turning brown.
If youve tried to grow mint, you might have also come across this issue. Even the easiest mint varieties out there are susceptible to attacks from pests, fungal diseases, and nutrient deficiencies – all of which can cause mint to go brown.
One of the most common causes is mint rust, a fungal disease that affects not only mint, but also marjoram and savory plants. However, this isnt the only cause of mint turning brown. Here, Ive outlined several causes behind this common problem and what you can do to resolve them.
Growing mint is a joy for any gardener. With its invigorating fragrance and flavor mint adds life to gardens food and beverages. However, those vibrant green leaves can suddenly turn brown, which is worrying. Let’s explore the common causes and solutions for mint leaves turning brown.
Overview of Main Causes
After analyzing the content from the provided URLs, the main causes of mint leaves turning brown seem to be
- Overwatering
- Underwatering
- Excessive sunlight
- Insufficient sunlight
- Fungal diseases
- Pest infestations
- Constricted roots
- Aging plants
- Lack of nutrients
- Overfertilization
- Salt buildup
- Cold drafts
Improper watering, whether too much or too little, is the most frequent culprit mentioned. Environmental factors like sunlight, temperature and humidity also play a big role. Diseases, pests, poor soil conditions, and the plant’s age can also lead to browning.
Symptoms of the Problem
How do you know if your mint is turning brown? Here are some telltale signs:
- Leaves are wilted, droopy or curled.
- Leaf edges and tips turn yellow or brown.
- Entire leaves become yellow, then brown.
- Brown spots, speckles or rust-colored spots appear on leaves.
- Leaves drop off easily.
- New growth is stunted.
If you notice any of these symptoms, your mint needs some troubleshooting to get back to its vibrant self.
Diagnosing the Cause
It’s important to identify the underlying cause before attempting to fix mint leaves turning brown. Here are some ways to diagnose the issue:
-
Check soil moisture. Stick your finger into the soil to see if it’s wet or dry. This gives clues about underwatering or overwatering.
-
Inspect the plant and leaves closely. Look for signs of pests like sticky residue, webs or bugs. Also check for fungal spots.
-
Consider environmental factors. Is the plant getting sufficient sunlight and protection from heat? Is humidity very low?
-
Check the roots. Are they crowded or restricted? Have they outgrown the container? This suggests constricted roots.
-
Review your care regimen. Have you fertilized recently? What type of water do you use? This provides insight on nutrients, salts, etc.
-
Evaluate the plant’s age and condition. Older mint may naturally brown as part of its lifecycle.
-
Rule out other stresses like cold drafts, hard water minerals, and improper soil pH.
How to Fix Mint Leaves Turning Brown
Once you’ve diagnosed the likely cause, take these steps to bring your mint back to life:
Improve Watering
-
Water only when soil is partly dry 1-2 inches deep. Provide thorough watering until it drains from bottom.
-
Create a consistent watering schedule such as 1-2 times per week. Stick to this routine.
-
Avoid waterlogged soil and don’t let mint sit in standing water.
Adjust Sunlight Exposure
-
Move mint to a shady spot if leaves are scorched or curled from excess sun.
-
Add a shade cloth or mesh cover to protect from intense afternoon sun.
-
If mint is stretching and weak, shift to a bright location with 5-6 hours of direct sun.
Increase Humidity
-
Mist leaves with room temperature water a couple times per day.
-
Place a humidifier nearby to maintain ambient moisture around 40-50%.
-
Grow mint with other plants to create a localized humid microclimate.
Fix Nutrient Deficiencies
-
Work compost into the soil to provide a slow-release nutrient boost.
-
Apply a balanced liquid fertilizer every 2-4 weeks during growing season.
-
If using tap water, allow it to sit out overnight before using to remove salts.
Prevent Fungal Diseases
-
Space plants out and prune dense growth to encourage air flow.
-
Remove any diseased foliage promptly. Disinfect shears between cuts.
-
Water at soil level instead of wetting leaves. Water early in the day.
Get Rid of Pests
-
Identify the pest and use appropriate organic control methods.
-
Wash leaves and stems with a strong spray of water to dislodge pests.
-
Apply horticultural oil or insecticidal soap if infestation is severe.
Fix Root Issues
-
Transplant into larger container if roots are crowded.
-
Loosen and untangle roots carefully before repotting.
-
Propagate new plants from cuttings to start fresh if roots are damaged.
Tolerate Natural Aging
-
Prune old stems and leaves to encourage new growth.
-
Fertilize regularly to provide extra nutrients.
-
Propagate new plants since old ones have a shorter lifespan.
Enjoy Vibrant and Healthy Mint
With some detective work and focused troubleshooting, you can get your mint back into top form. Pay close attention to moisture, sunlight and humidity which mint is particularly sensitive to. Rule out pests, diseases and nutrition problems. Don’t hesitate to start new plants if aging ones can’t be revived. With just a bit of care, you’ll enjoy lush and flavorful mint leaves again.
What is mint rust? (Image credit: Dave Bevan via Alamy)
I discovered mint rust was the cause behind my mint turning brown. Its a fungal disease caused by the fungus Puccinia menthae which causes mint plants (and some others) to have orange and brown pustules and patches on their leaves, giving a rusty appearance.
Mint rust is primarily a result of overly wet and humid conditions, where the fungus thrives. It can also spread through debris, soil, and contact with infected plants.
The result can distort shoots and cause defoliation, as well as browning foliage.
When I noticed mint rust, I acted fast to prevent spread. This included pruning mint to remove infected plants before black resting spores formed and infected the soil. Luckily, I was growing my mint in a pot, so this contained the disease in early stages. Growing mint indoors is likely to also contain the issue.
If your infected mint is growing in a bed with other plants, make sure to remove infected rhizomes and consider reportioning remaining healthy stems elsewhere to reduce likelihood of infection.
Another treatment option is immersing rhizomes in hot water of 111ºF for around 10 minutes. Make sure to use a water thermometer (from Amazon) to ensure the temperature doesnt go any higher than 111ºF – this could kill off the plant.
Other reasons your mint is turning brown (Image credit: Getty Images/PaulMaguire)
If you dont believe your mint is turning browning due to mint rust, theres another likely explanation.
One of the most common herb gardening mistakes is getting watering wrong. When it comes to mint growing, overwatering can lead to root rot. At the same time, this herb doesnt like to grow in a dry environment.
To get moisture levels right, I recommend using this soil moisture meter from Amazon. Top your mint up with water when the meter indicates the soil is dry one or two inches down.
Mint turning brown can also be a result of leaf scorch. This herb appreciates plenty of sunlight, but theyre also quite shade-tolerant, with sensitive leaves that dont do well in direct sun for too long at a time.
To resolve this problem, simply reposition your mint plant somewhere more protected from the sun.
It could also be that your mint is browning from a lack of essential plant nutrients. In particular, nitrogen is important for healthy vegetative growth, but a good balanced fertilizer (from Amazon) will give your mint a boost of all the nutrients it needs.
In a similar vein, your mint could be turning brown from a poor soil type and needing repotting, if grown in containers. As a herbaceous perennial, you can expect your mint to get bigger each year, so make sure to repot with a larger container as needed to support its growth.
How To Restore A Mint Plant
FAQ
What to do when mint leaves turn brown?
Mint turning brown can also be a result of leaf scorch. This herb appreciates plenty of sunlight, but they’re also quite shade-tolerant, with sensitive leaves that don’t do well in direct sun for too long at a time. To resolve this problem, simply reposition your mint plant somewhere more protected from the sun.
What are the signs of overwatering in mint?
When this species receives too much water, its stems and leaves may begin to wilt and turn from green to yellow. Overwatering over a prolonged period may also lead to diseases such as root rot, mold, and mildew, all of which can kill your plant.
How do you fix brown leaves?
If the roots are not bound together and look healthy, your plant just needs a bit more water to keep its foliage green and healthy. Repot your plant, either in its original planter or a larger one if necessary. Prune away any brown or wilted leaves so your plant can direct its energy to producing new, healthy growth.