Growing mint is a joy for any gardener. Mint brings gardens, food, and drinks to life with its energizing smell and taste. But those bright green leaves can turn brown all of a sudden, which is scary. Let’s look at the most common reasons why mint leaves turn brown and how to fix them.
Overview of Main Causes
Based on what I read at the given URLs, the main reasons why mint leaves turn 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
The most common reason given is improper watering, either too much or too little. Sunlight, temperature, and humidity in the environment also play a big role. Browning can also be caused by diseases, pests, bad soil, and the plant’s age.
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:
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Check soil moisture. Stick your finger into the soil to see if it’s wet or dry. This gives clues about underwatering or overwatering.
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Inspect the plant and leaves closely. Look for bugs, sticky stuff, webs, or other signs of pests. Also check for fungal spots.
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Consider environmental factors. Is the plant getting sufficient sunlight and protection from heat? Is humidity very low?
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Check the roots. Are they crowded or restricted? Have they outgrown the container? This suggests constricted roots.
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Review your care regimen. Have you fertilized recently? What type of water do you use? This provides insight on nutrients, salts, etc.
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Evaluate the plant’s age and condition. Older mint may naturally brown as part of its lifecycle.
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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
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Water only when soil is partly dry 1-2 inches deep. Provide thorough watering until it drains from bottom.
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Create a consistent watering schedule such as 1-2 times per week. Stick to this routine.
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Avoid waterlogged soil and don’t let mint sit in standing water.
Adjust Sunlight Exposure
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Move mint to a shady spot if leaves are scorched or curled from excess sun.
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Add a shade cloth or mesh cover to protect from intense afternoon sun.
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If mint is stretching and weak, shift to a bright location with 5-6 hours of direct sun.
Increase Humidity
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Mist leaves with room temperature water a couple times per day.
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Place a humidifier nearby to maintain ambient moisture around 40-50%.
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Grow mint with other plants to create a localized humid microclimate.
Fix Nutrient Deficiencies
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Work compost into the soil to provide a slow-release nutrient boost.
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Apply a balanced liquid fertilizer every 2-4 weeks during growing season.
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If using tap water, allow it to sit out overnight before using to remove salts.
Prevent Fungal Diseases
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Space plants out and prune dense growth to encourage air flow.
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Remove any diseased foliage promptly. Disinfect shears between cuts.
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Water at soil level instead of wetting leaves. Water early in the day.
Get Rid of Pests
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Identify the pest and use appropriate organic control methods.
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Wash leaves and stems with a strong spray of water to dislodge pests.
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Apply horticultural oil or insecticidal soap if infestation is severe.
Fix Root Issues
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Transplant into larger container if roots are crowded.
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Loosen and untangle roots carefully before repotting.
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Propagate new plants from cuttings to start fresh if roots are damaged.
Tolerate Natural Aging
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Prune old stems and leaves to encourage new growth.
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Fertilize regularly to provide extra nutrients.
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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. You can get a water thermometer from Amazon to make sure the temperature doesn’t rise above 111ºF, which could kill 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.
Similarly, if your mint is grown in pots and is turning brown, it may be because the soil isn’t good enough and needs to be re-potted. 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?
Its stems and leaves may start to wilt and turn from green to yellow when it gets too much water. If you water your plant too much for too long, it could get diseases like root rot, mold, and mildew, all of which are fatal.
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. You can help your plant grow new, healthy leaves by cutting off any that are brown or wilting.