Tomatillo plants are a rewarding addition to many gardens. A common concern for gardeners is when tomatillo leaves begin to turn yellow. This yellowing, known as chlorosis, is a visual symptom indicating an underlying issue within the plant or its environment. Promptly addressing this symptom can help restore plant health and ensure a bountiful harvest.
Common Causes of Yellowing Tomatillo Leaves and How to Address Them
Nutrient Deficiencies
Yellowing tomatillo leaves often signal a lack of essential nutrients. Nitrogen deficiency typically causes older, lower leaves to yellow uniformly. To correct this, apply a balanced fertilizer with higher nitrogen or add organic compost.
Iron deficiency often manifests as yellowing between the veins of newer leaves, with veins remaining green. This pattern, called interveinal chlorosis, indicates the plant struggles to produce chlorophyll. Magnesium deficiency also causes interveinal yellowing, usually on older leaves first. Incorporate Epsom salts (magnesium sulfate) or dolomitic lime into the soil to remedy a magnesium shortage.
Watering Issues
Both overwatering and underwatering can lead to yellowing tomatillo leaves. Overwatering suffocates roots by displacing oxygen, preventing nutrient absorption and leading to root rot. Symptoms include overall yellowing and wilting, even with soggy soil. Allow the soil to dry slightly between waterings and ensure proper drainage to prevent this.
Underwatering deprives the plant of moisture needed for metabolic processes, resulting in dry, crispy leaves that gradually yellow. The soil will feel dry to the touch. Establish a consistent watering schedule, provide deep waterings, and regularly check soil moisture by feeling the top few inches to maintain hydration.
Pests
Certain pests cause tomatillo leaves to yellow by feeding on the plant’s sap. Spider mites, aphids, and whiteflies are common culprits, extracting vital fluids and leading to discoloration and weakened growth. Identify these pests by looking for fine webbing, sticky honeydew, or the insects themselves, often on leaf undersides. A strong water spray can dislodge many soft-bodied pests, while insecticidal soap or neem oil provides effective organic control.
Diseases
Several diseases can manifest as yellowing leaves, often with other specific symptoms. Early blight causes small yellow spots that enlarge, turn brown, and lead to leaf wilting. Fusarium wilt causes widespread yellowing, wilting, and stunted growth. Bacterial spot may present with yellowing alongside distinct leaf spots.
Prevention includes crop rotation, selecting disease-resistant varieties, and maintaining good garden sanitation, such as removing infected plant debris. Fungicides may be effective for some fungal diseases, but viral or bacterial infections often require removing affected plants to prevent spread.
Environmental Stressors
Tomatillos can also exhibit yellowing leaves due to environmental stressors. Extreme temperatures, both hot and cold, disrupt plant functions and cause leaves to yellow. Transplant shock, from moving plants, can temporarily inhibit nutrient uptake and lead to yellowing. Sudden light changes, like moving a plant from shade to intense direct sun without acclimatization, also cause stress. Provide shade during heatwaves, protect plants from cold snaps with row covers, and gradually expose transplanted seedlings to new light levels to mitigate these stresses.
General Care Practices to Prevent Yellowing
Proactive care is the most effective way to prevent tomatillo leaves from yellowing. Begin with proper soil preparation, ensuring the planting site has well-draining, rich loamy soil amended with compost. Consistent watering is key, aiming for about 1 to 1.5 inches of water per week, applied deeply at the base of the plant to keep the soil consistently moist but not waterlogged.
Regular, balanced fertilization throughout the growing season ensures the plant receives all necessary nutrients. Tomatillos thrive in full sun, requiring at least six to eight hours of direct sunlight daily. Adequate spacing between plants promotes good air circulation, helping prevent fungal diseases that contribute to yellowing. These practices create a robust plant less susceptible to environmental stresses, pests, and diseases.
When to Worry About Yellow Leaves
It is natural for some older, lower leaves to yellow and drop off as the plant matures and new growth emerges. This is a normal part of the plant’s life cycle and typically not a concern. However, widespread or sudden yellowing across many leaves, especially new growth, indicates a more serious underlying issue requiring immediate attention. Observing the pattern of yellowing and accompanying symptoms provides clues to diagnose the problem. Many causes of yellowing leaves are treatable, and timely intervention helps tomatillo plants recover and continue to produce fruit.