Why Tomato Plants Turn Purple

Tomato plants are popular garden vegetables because they have delicious fruits that are rich in essential nutrients. However, sometimes you may notice that the leaves or stems of your tomato plants turn purple instead of their usual green color. In this article, we will take a closer look at the reasons behind this phenomenon.

1. Genetics

The first reason why tomato plants may turn purple is simply because of their genetics. Some tomato varieties are naturally more prone to developing purple pigmentation due to their genetic makeup. This is often referred to as "anthocyanin expression," as anthocyanins are the pigments responsible for the purple coloration.

Genetic coloration is not necessarily a negative thing, and in fact, some gardeners actually seek out and cultivate purple tomato varieties because of their unique appearance and flavor.

2. Nutrient Deficiencies

Another potential reason why tomato plants turn purple is due to nutrient deficiencies in the soil. Specifically, a lack of phosphorus or potassium can cause your plants to produce purple pigmentation. Both of these nutrients are essential for plant growth and fruit production.

If you suspect that your soil may be lacking in these nutrients, you can take steps to improve it. Testing your soil is a good first step, as it can help you identify what nutrients your plants may be lacking. Adding fertilizer and compost can also help provide the necessary nutrients and improve the overall health of your plants.

3. Cold Temperatures

Cold temperatures can also cause tomato plants to turn purple. If your tomato plants are exposed to temperatures below 50 degrees Fahrenheit (10 degrees Celsius), they may develop purple pigmentation on their leaves and stems.

This is because low temperatures can interfere with the plant's ability to take up phosphorus, which as we already established, is essential for healthy plants. If you live in a cooler climate, consider planting varieties that are more tolerant of cooler temperatures.

4. Pests and Diseases

Pests and diseases can also cause tomato plants to turn purple. One common issue is verticillium wilt, a fungal disease that can cause the leaves and stems of a plant to turn yellow, wilt, and eventually turn purple. Additionally, aphids and spider mites can sap the nutrients from a plant and cause it to develop purple pigmentation.

To prevent and address pest and disease issues, it's important to practice good gardening hygiene, such as keeping your garden clean and using natural remedies like neem oil and insecticidal soap when necessary.

Conclusion

Tomato plants turning purple may be a cause for concern, but it's not always a sign of a major problem. Sometimes, it's just a natural expression of the plant's genetics, while other times it may indicate a nutrient deficiency, cold temperatures, or pest and disease issues. By taking the necessary steps to keep your plants healthy and happy, you can enjoy a bountiful harvest of delicious, vibrant tomatoes.