Tomato leaves can curl for several reasons, each pointing to different potential issues affecting the plant's health.
When tomatoes experience excessive heat, they may curl their leaves to reduce surface area and minimize water loss through transpiration. Similarly, intense sunlight or sudden temperature fluctuations can trigger leaf curling as the plant attempts to protect itself from harsh conditions.
Addressing environmental stress often involves providing light shade, ensuring consistent, deep watering, and protecting plants from extreme weather.
Another frequent cause of leaf curling is pest infestations or nutrient deficiencies. Aphids, whiteflies, and other pests can cause leaves to curl as they feed on plant sap and introduce harmful substances.
Deficiencies in essential nutrients, particularly potassium and calcium, can lead to symptoms like leaf curling and distortion. See quote box below.
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Nutrient deficiencies or imbalances in the soil can also cause tomato leaves to curl. A lack of potassium, for example, can lead to leaf curling and edge scorching, while calcium deficiency can cause leaf curling along with blossom end rot. Over-fertilization or imbalanced nutrient levels can disrupt the plant’s normal growth processes, leading to various symptoms, including leaf curl.