Tomato plants are a common fruit grown in home gardens. This is because these plants look stunning when present in small indoor or outdoor fields.
But Tomato plants can often face challenges when growing, such as the occurrence of purple leaves.
These challenges are usually caused by a lack of attention or a lack of some form of nutrition.
Sometimes it can be hard to spot what the problem may be, but once found, it can be easily tackled.
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Why Are My Tomato Plants Turning Purple?
The leaves on your Tomato plants turn purple because of a lack of phosphorus in the soil. Purple tomato leaves can also happen due to pH imbalances in the soil. Other causes include temperatures below sixty degrees Fahrenheit (15 degrees Celsius) and exposure to high-intensity light.
Reasons for Purple Tomato Plant
Phosphorus Deficiency
Phosphorus deficiency is one of the biggest causes behind tomato plants having purple foliage.
The purple color may even spread throughout the plant and will be more prominent on the bottom side.
Phosphorus deficiency may occur most often during winter or spring.
This is because during these two seasons, the soil is cold, and the tomato plant’s roots will not be fully developed.
This element’s a crucial nutrient for the tomato plant’s roots, as well as flowers in tomato plants. This is why it’s essential to know what is the reason behind the lack of phosphorus in the plant.
Usually, phosphorus deficiency in tomato plants has three main causes.
One is the absence of phosphorus in the soil, the second is imbalances in soil pH, and the third is cold soil.
Two out of the three conditions can be discovered through a simple soil test, or a thermometer can be used to test for cold soil.
Absence of Phosphorus in the Soil
Phosphorus deficiency that has been caused by the soil lacking phosphorus is usually because gardeners do not practice crop rotation.
It can also be caused due to a lack of organic materials or usage of fertilizers with low phosphorus levels.
When you plant your tomato plants in the same area, you can cause the phosphorus levels to drop in the soil.
To avoid this from happening, crop rotation should be done. Crop rotation means planting the crop in one area of the garden and then moving it into the other area next year.
Soil pH Imbalance
Soil pH imbalances can also cause phosphorus deficiency in plants. Every plant has an optimal growth pH range.
For Tomato plants, according to the USDA, it likes slightly acidic soil. This means the soil should have a pH range of 6.2 to 6.8 for Tomato plants.
If the soil’s pH is too high or too low, it can disturb the plants’ ability to absorb phosphorus from the soil.
This can occur even if there are enough nutrients in the soil. Lack of absorption from the soil can cause phosphorus deficiency in your Tomato plant; thus, causing purple leaves.
Cold Soil
Cold soil is the third reason why your tomato plant is turning purple.
Cold soil can also prevent your plant from absorbing phosphorus from the soil.
This happens even if there is phosphorus in the soil, but if the soil is too cold, the bacteria on your plant’s roots will not convert phosphorus from the soil.
The bacteria are responsible for converting phosphorus into a form that can be consumed by your tomato plant. Thus, if not converted, it cannot be consumed.
Intense Light Exposure
If your tomato plant is exposed to intense light when it is in its growing stage, then it can develop purple leaves. This can occur in both artificial light and sunlight.
When exposed to intense light, your tomato plant tries to protect itself. It does so by producing anthocyanins that turn the leaves purple.
Treatment for Purple Tomato Plant
Treating less phosphorus in soil is simple as you just need to replace the nutrients every year by adding fertilizers that have high phosphorus content.
You can also use compost as it is organic and contains high phosphorus as well.
Aged manure is another alternative to compost and fertilizer. It, too, is organic.
For pH imbalances, you will need to add lime, which is calcium carbonate, in the soil to increase pH level (reduce acidity) if the pH level is low.
Calcium addition should not be in high amounts; this is because the access of it will prevent your tomato plant from absorbing potassium and magnesium.
If the pH of the soil is high (alkaline or basic), you lower it with the addition of sulfur into the soil. It is also essential to know that adding fertilizers or any other substance can alter the pH of the soil.
Thus, before adding anything, remember to check the pH level before and after.
For cold soil, try to regulate the temperature back to any level above 60-degrees Fahrenheit (15 degrees Celsius).
You can either transport your tomato plant to another location or start planting tomato plant seeds indoors.
This way, you ensure that the soil is at its optimum temperature for germination, and this will also prevent phosphorus deficiency.
Treatment for Intense Light Exposure
If you have planted your tomato plant indoors, then reduce the light intensity it receives from artificial lighting through the controls.
Natural light can be reduced by moving the plant to another location.
If you place the tomato plant outdoors, reduce the light intensity through row covers.
Row covers can reduce the light intensity by fifty to ninety-five percent. Row covers also protect the plant against pests and the cold.
You can also use shade cloths to reduce the light intensity.
Some shade cloths only allow five percent of light to pass through, while others can allow up to ninety-five percent of light to pass through.
Frequently Asked Questions about Why Tomato Plants Turn Purple
Can pests also cause Tomato plants to turn purple?
Pests can ultimately cause your tomato plant to turn purple. This is because pests can stress the plant, and as an effect of this stress, the plant turns purple.
Can diseases cause Tomato plants to turn purple?
Tomato plants can also turn purple due to diseases. Common viruses for purple tomato plants include a curly top virus, Tomato purple leaf disorder, and Tomato spotted wilt virus.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.