Mint Plant Turning Yellow, Brown, Purple or Black – SAVE IT

Nothing hurts more than seeing your lush green mint plant turning yellow, black, brown, or purple. A mint plant can change its color even when we are taking care of it properly. It is because many underlying reasons are causing your mint plant to change its color. I’ve been growing mint plants in my garden for years. Here is a guide based on my experience explaining the reason and solutions to this problem.

Mint Plant Turning Yellow, Brown, Purple Or Black

There are some common reasons which can result in a dying mint plant, let’s find out why your mint plant is changing color and how you can take care of that.

Why Does Mint Plant Turn Purple?

It is quite depressing to see your well-grown bush mint plant turning purple. Many factors could make the mint leaves turn purple, but the most common is a phosphorus deficiency. If the soil lacks phosphorus, it will make mint tris turn purple. The situation gets even worse when your plant is not getting proper moisture and the favorable pH level between 6-7.


  • Immediately cut down the stems with purple leaves to 1 inch above the ground. Pruning the unhealthy parts of plants will help you slow down the disease spread.
  • Adding a fertilizer rich in phosphorus is another solution to the problem. Bone meal manure or compost is an organic fertilizer rich in phosphorus. You can either make it at home or buy it from a nearby nursery.
  • Quick-release phosphorus commercial fertilizer is another instant solution. Sprinkle 1 tablespoon of quick-release fertilizer around each plant.
  • I personally prefer homemade organic fertilizer to avoid over-fertilization.

Why Mint Leaves Turn Yellow?

Mint is one of my favorite herbs and has always been part of my garden. The most common problem that I noticed with mint is that its leaves turn yellow. The major reason behind this problem is the presence of excessive moisture in the soil. The overwatering tends to rot the plant roots or choke them, and its leaves turn yellow.

Too much shade and low nitrogen levels in the soil also make mint leaves turn yellow. Additionally, underwatering and poor soil conditions like low levels of nutrients can also trigger this problem. Rust fungus that grows in excessive moisture, aphids, and extreme cold also make mint leaves turn yellow.


  • If you have not fertilized the mint plant for a long time, it is the best time to fertilize it with a nitrogen-rich fertilizer. The fertilizer that I found most impressive to treat yellow mint plants is aged cow manure. It is an organic fertilizer rich in carbon and nitrogen. You can also use quick-release nitrogen fertilizers or organic fish emulsion fertilizers.
  • Do not overwater plants and regularly check the moisture level in the soil. You can add well-rotted compost or dry leaves to enhance the drainage of the soil. If you have potted mint plants, regularly check if they have proper drainage or not. Clogged drainage leads to excessive moisture.
  • Trim back the yellow leaves before the extreme cold. The stems and roots will go dormant and will grow in the spring season.

Why Mint Plants Turn Brown?

Mint turning brown is a rare but critical situation. The major factor that causes mint leaves to turn brown is the fungal attacks. Rust Fungus attack can severely damage the mint health causing its leaves to turn brown. The Rust fungus attacks in the presence of excessive moisture and high humidity levels. Also, when you overwater the plants and leaves retain water drops, it becomes easier for fungus to invade the leaves.

If you observe that the plant is healthier from the outside, but the inner part turns brown, Rust is not a reason. The inner part of the plant doesn’t get enough sunlight and is prone to high humidity levels, making the mint plant turn brown.


  • To prevent Rust Fungal disease, it is important to provide your plant with adequate sunlight and maximum drainage.
  • It will regularize the moisture level and reduce fungal growth. Additionally, you should change the way of watering.
  • Do not water on the top of leaves, and make sure water drops are not stocked on the leaves.
  • If the inner part of the plant is turning brown simply trim back this part. Regularly check for brown leaves and stem inside the plant and trim them off.

Why Does the Mint Plant Turn Black?

If any of the above-mentioned situations is not controlled, it will cause the mint to dry up and rot, and it will turn black. However, mint paint can turn black when exposed to high temperatures and direct sunlight for a long time. Overfertilization and higher pH of the soil will also make the mint plant change its color to black.


  • Do not expose the mint plant to direct sunlight for a long time. It is critical to maintaining the temperature between 25-35 degrees celsius.
  • If the pH of the soil is alkaline, you can add acidifying nitrogen or sphagnum peat to the soil to neutralize the pH.
  • Do not over-fertilize the mint plant with quick-release commercial fertilizers. Always use organic fertilizer when needed.


What does Overwatered mint look like?

An overwatered mint plant looks dangling with yellow leaves. Overwatering mint plants can also trigger the Rust Fungus to invade the mint plant and change its color to brown.

How do you fix an overwatered mint plant?

If you have a potted mint plant, check its drainage holes. If daring holes are blocked, open them. If these holes are inadequate, screw extra holes to improve drainage. If you have ground planted mint, add the well-rotted compost to the soil or dry leaves to absorb excessive moisture and improve the soil’s drainage.


Mint is an easy to grow plant, but our little mistakes can cause the mint plant to change its color. I’m hopeful that this guide will help you keep your mint plant from turning yellow, brown, black, or purple.