Mint leaves are known for their freshness and vibrant green color. That is why it can feel strange to see your mint plant turning purple.
Here are the possible causes with solutions for your mint leaves turning purple.
The main reason why your mint leaves may turn purple is because of the lack of nutrients mainly phosphorus.
Mint needs soil that is rich in phosphorous, nitrogen, and potassium to provide it with sufficient nutrients.
The soil should be with a pH between 6 and 7. If there is a deficiency in even one of the nutrients, the mint will not be able to reach that level of pH, leading to purple leaves.
Most of the time, it is a deficiency of phosphorous that causes the purple leaves. That is because phosphorous is needed to produce energy, for nucleic acids, and sugars.
Sometimes, cold soil or soil that is too wet and soggy can also prevent the plants from properly absorbing all the nutrients.
That is why, sometimes even when your soil has all the nutrients, the plant will still not be able to benefit from them.
High acidity in the soil or too much iron in the soil can also prevent your plant from absorbing the nutrients from the soil.
A nutrient deficiency will be clearly visible in your plant, as the plant will struggle to survive.
The growth of the plant will be affected, along with the color of the leaves. If not acted upon quickly, the plant could die.
How to be sure of a phosphorous deficiency?
You can run a soil test or analysis to figure out the soil deficiency. You can do this process in a soil lab, or even at home with soil test kits available in the market.
If you use the kit at home, read the instructions carefully and test the soil. This tool will help you know which and how much of the nutrients are lacking.
Firstly, remove the affected leaves. Cut the leaves at the base of the stems to prevent any damage to the plant tissues.
If the phosphorous levels are low, you can get a fertilizer that is rich in phosphorous. You can use bone meal, compost, or manure.
Make sure that the soil is ideal for your plant to grow because if the soil is unfit, any amount of nutrients you add will not help the plant.
If the soil is too cold, move it to a warmer place. Make sure you do not overwater the plant.
If the pH of the soil is too low, use lime. Lime will raise the pH levels of the soil. Keep the levels between 6 and 7. This will also keep the iron in the soil to an optimal level.
It might seem that using a lot of fertilizers will only benefit the plant. But that is never the case. Anything in excess isn’t good. This also applies to fertilizers.
Using excessive fertilizers can cause a lot of problems to the plants including mint leaves turning purple.
If you use too much fertilizer, your plant will grow rapidly, however, the roots of the plant will not be able to match its growth.
This will result in a plant that is growing with roots that are not able to provide sufficient water and nutrients to the entire plant. This will leave you with a mint plant that is insufficient in vitamins and minerals.
Mint will not react well to a shortage of nutrients, resulting in a plant that has darkening or purple leaves.
Your mint will also become less flavorful and aromatic, which is not a good thing seeing as how mint is used in food especially for its flavor.
There are a few easy solutions to the problem of overfertilization.
Firstly, stop fertilizing the plant immediately. If you can see your plant affected due to overfertilization, do not provide it with any more fertilizer for at least a month.
In case, you are able to see the fertilizer in the soil, remove it so that only a limited amount is left for your plant to absorb.
If your plant is damaged in places, remove the affected parts so that the roots of your plant can provide nourishment to the parts that need it.
The mint likes and needs sunlight to grow. However, while it enjoys some light, exposure to too much direct sunlight can do more harm than good to the mint.
Mint prefers partial shade to thrive. Unlike a lot of herbs, which require a lot of sunlight throughout the day, the mint needs shaded places to grow healthy.
If you manage to frequently water the mint and keep the soil moist but well-drained, it is possible for the mint to grow in a sunny place.
If that is not the case, there is no doubt that your mint plant will suffer from sunburns.
A sunburnt plant will not be able to keep up with the green color of its leaves, turning dark and brittle in the areas where it has been affected.
To fix a sunburnt mint plant, change its location. Choose a place that is sunny, but make sure that your mint isn’t sitting in direct sunlight. Keep it in a shaded area of a sunlit place.
If you absolutely have to keep your mint in a place that is exposed to sunlight, make sure it is watered frequently.
Check for the changes in sunlight every day as it passes through seasons.
The position of sunlight will change gradually throughout the year, so you might need to move your mint during certain months if in case it suddenly starts getting too much sunlight.
While too much sunlight can burn the mint leaves to a crisp, the mint cannot function in insufficient light as well.
If you keep the mint in a dark corner of the house so as to protect it from sunlight, the plant is still not going to be able to stay green and turn mint leaves purple.
Plants need sunlight for the process of photosynthesis. If there is no light, there will be no photosynthesis, the process which helps keep the plants green and nourished.
So, the mint plant needs sunlight, just not direct exposure to the sun.
Move the plant to a place that gets plenty of sunlight. Keep the plant in a shaded part of that place.
If you don’t have a place that is ideally lit, you can move the plant to a lighter place during the day and move it back to the shadows during the night.
Remember never to place the plant in direct sunlight at any time throughout the day.
Artificial lamps can also be used to provide lights to plants that do not have the ideal lighting conditions. There are some lamps that are specifically designed for growing plants.
Overwatering or underwatering
Every plant needs a certain amount of water, and if you meet that need, the plant can grow really well.
A lot of times, people forget to water their plants for days and then overwater them to compensate for all the days they didn’t water.
This is the worst thing to do to your plant, as it only harms the plant.
Too much water all of a sudden can overwhelm the plant as it flushes out all the nutrients in the soil.
Watering more than needed for a prolonged time can lead to rotting roots, which in turn leads to more problems.
On the other hand, if you underwater the plant, it will lead to dry soil and water will not be able to seep into the root system of the mint.
The roots will struggle to get nutrients from the soil because of this reason. This will result in a dried-out and parched mint.
Overwatering or underwatering leads to a lack of nutrients which causes a lot of problems for the mint.
When plants suffer, they will give you signs. The mint will struggle to sustain itself. The leaves will be affected first. They will become dark or purple, shrivel, droop or just start falling off.
How much water does mint need?
Mint needs a lot of water, at least 2 or 3 days a week. You might need to water more if you live in a dry area.
Make sure to water the plant in the morning so that it has time to evaporate. Check the soil before watering.
If the soil is still wet, it is possible that you have bad drainage, and watering on top of that could result in purple leaves.
Mint requires moist soil, but it should not be too wet. If the soil on top appears soggy, you might be overwatering it.
One way to check is to push your finger through the soil. If it goes in easily and comes clean, your soil is perfect for the mint.
Avoid watering directly on the leaves. Instead, water is at the base of the plant.
Mint plant likes moist soil, but the soil also needs to be well-drained. Without proper drainage, the roots of the mint will become soggy and rot.
This will deteriorate the condition of the plant, killing it slowly. It will cause pigmentation of the leaves, which will turn purple.
You should plant your mint in containers that can drain well. The pots should have drainage holes at the bottom for any excess water to flow out easily.
The pots should also be large in size, at least 10 inches deep.
The soil could also be a problem. Some soil does not drain as well as others. In this case, mix your soil with sand or perlite to improve the drainage of your plant.
Insects can be a good reason for your plant leaves turning purple. Insects feed off your plants, sucking out all the juices and nutrients from the plant.
This robs your plants of vital nutrients and chlorophyll, leading to decolorization of the leaves that make them purple, as well as poor health of your plant.
You will mostly find thrips, spider mites, and aphids around your mint plant.
The plant-based insecticide is a great remedy to get rid of insects. This ensures that your plant isn’t harmed while removing the insects.
You can use rubbing alcohol on the affected areas. However, it can be drying, so make sure to use it with caution.
Homemade, organic insecticides like rosemary oil or garlic water can also be useful to get rid of these pests.
Sometimes, just spraying the plant with a steady stream of water can help get rid of these insects.
Temperature changes do not affect indoor plants as much as outdoor ones. But they can still impact the overall health and appearance of your plant.
Mint enjoys a temperature between 55 and 70°F (13-21°C). In winters or in a cold climate, the mint will not be able to process the nutrients in the soil as effectively.
Similarly, in the summers or a hot climate, your mint can suffer from wilting or drying out. Either of these issues can affect the color of your plant.
Keep a check on the temperatures during changes in seasons.
If it gets too cold, move the plant to a warmer place in the house. Keep it away from windows and doors which are draughty.
In case it is too cold, you can use an indoor heater to increase the temperature, but make sure to not keep it too close to the plant.
If it is too hot, move the mint to a cooler area. You can also keep the windows shut during the day so as to keep off hot air and open them at night to let in some cool air.