The yellowing of tomato plant leaves can be caused by several common factors:
- Nutrient deficiencies, especially lack of nitrogen, potassium, magnesium, or iron, which lead to chlorosis (yellowing) of leaves. Nitrogen deficiency typically causes older lower leaves to turn yellow first as nitrogen is mobile within the plant.
- Overwatering or underwatering can stress the plant and cause leaves to yellow. Overwatering can lead to root rot which hampers nutrient uptake, while underwatering causes drought stress.
- Diseases such as early blight, a soil-borne fungal infection, often start with yellow spots on lower leaves and progress to browning and leaf death.
- Environmental stresses including transplant shock, insufficient sunlight, or frost damage can also turn leaves yellow. Transplant shock often causes yellowing lower leaves temporarily, while lack of sunlight and frost damage cause yellowing with other signs like curling or blackened leaves.
- Pests like aphids and mites can stress the tomato plant and cause yellowing leaves alongside curling or spotting.
To diagnose and address the issue:
- Check plant watering to avoid excess or insufficient moisture.
- Ensure the plant receives at least 6 hours of sunlight daily.
- Fertilize with balanced nutrients rich in nitrogen and micronutrients like magnesium.
- Remove yellowing lower leaves to prevent disease spread.
- Inspect for pest infestation and treat organically if needed.
- Avoid planting tomatoes too early to prevent transplant shock and protect from frost.
This overview covers the most typical causes and remedies for yellowing tomato leaves, helping identify and fix the problem to keep plants healthy and productive.
