Coffee plants (_Coffea arabica_ and _Coffea canephora_) are popular houseplants, and their vibrant green leaves sometimes turn yellow. While concerning, yellowing leaves often signal a solvable issue. Understanding the underlying reasons can help restore your coffee plant to health.
Common Causes of Yellowing Coffee Plant Leaves
Numerous factors can contribute to the yellowing of coffee plant leaves, from environmental conditions to nutrient availability. Identifying the specific cause is the first step toward effective treatment.
Watering Imbalances
Overwatering is a frequent culprit for yellowing leaves. When soil remains waterlogged, roots are deprived of oxygen, leading to root rot and overall yellowing. The roots essentially suffocate, impairing their ability to absorb nutrients and water.
Underwatering also causes yellowing, often with crispy, dry leaves, yellowing from tips or edges. A completely dry soil prevents water absorption, hindering leaf health.
Nutritional Deficiencies
Lack of specific nutrients can lead to chlorosis, or yellowing. Nitrogen deficiency causes uniform yellowing of older leaves, including veins, as the plant reallocates this mobile nutrient.
Iron deficiency results in interveinal chlorosis (tissue between veins turns pale yellow or white, veins remain green), usually affecting new leaves. Magnesium deficiency also causes interveinal yellowing, typically on older leaves.
Light Stress
Both excessive and insufficient light can yellow coffee plant leaves. Direct, intense sunlight can scorch leaves, causing a pale yellow or bleached appearance.
Coffee plants naturally grow as understory plants, preferring bright, indirect light. Insufficient light results in overall pale yellowing and leggy growth due to poor photosynthesis.
Temperature and Humidity Issues
Coffee plants thrive in stable, warm, and humid conditions. Extreme temperatures (too cold or too hot) induce stress and cause leaf yellowing.
Temperatures below 60°F (15°C) or above 80°F (27°C) can be particularly stressful. Low humidity, common indoors, can also lead to leaf yellowing and crispy edges.
Pests and Diseases
Pest infestations contribute to leaf discoloration and yellowing by feeding on plant sap. Common pests like spider mites, mealybugs, and scale insects extract nutrients, weakening the plant and causing yellowing.
Fungal diseases, such as anthracnose, can also cause spots and discoloration that may include yellowing areas.
Potting Medium Problems
Compacted soil restricts root growth and reduces oxygen, leading to yellow leaves. Poor drainage, often from compacted soil or inadequate pot design, causes waterlogging and root rot, directly leading to leaf yellowing.
Incorrect soil pH can also hinder nutrient uptake, resulting in deficiencies and yellowing foliage.
Diagnosing the Specific Cause
Diagnosing yellowing coffee plant leaves involves careful observation. Examine the pattern of yellowing.
Uniform yellowing across the entire leaf suggests overwatering or nitrogen deficiency. Interveinal chlorosis (yellowing between green veins) often points to iron or magnesium deficiencies.
Consider the location of affected leaves. Yellowing on older, lower leaves often indicates mobile nutrient deficiency (e.g., nitrogen, magnesium), as the plant moves resources to new growth.
Conversely, yellowing on new growth or upper leaves suggests immobile nutrient deficiencies like iron, which the plant cannot redistribute. Observe soil moisture: consistently wet soil signifies overwatering, while bone-dry soil points to underwatering.
Inspect undersides of leaves and stems for pests like spider mites (tiny webs) or mealybugs (cottony masses).
Solutions for Yellowing Leaves
Addressing yellowing leaves involves targeted interventions based on the identified cause. For overwatering, allow the top inch or two of soil to dry between waterings, ensuring adequate drainage.
If underwatering, provide thorough watering until drainage, then maintain consistent moisture (evenly moist, not soggy).
To correct nutritional deficiencies, apply a balanced, water-soluble fertilizer during the growing season (every 2-4 weeks). For specific deficiencies, consider a chelated iron supplement or a higher nitrogen fertilizer.
Adjust light exposure: move the plant to bright, indirect light, away from harsh direct sun or overly dim corners. If light is insufficient, a grow light can supplement natural light.
To mitigate temperature and humidity stress, maintain indoor temperatures between 60°F and 75°F (16°C and 24°C), avoiding drafts. Increase humidity using a humidifier, pebble tray, or by grouping plants.
If pests are present, wipe them away with a damp cloth or use insecticidal soap. For potting medium issues, consider repotting with fresh, well-draining, slightly acidic soil mixed with organic matter, peat moss, or perlite to improve aeration and drainage.
Preventing Future Yellowing
Proactive care prevents future yellowing. Establishing a consistent watering routine, allowing the top soil layer to dry slightly between waterings, maintains appropriate moisture without waterlogging or dehydration.
Regular fertilization during the active growing season (spring and summer) provides necessary nutrients for robust foliage and plant health. Providing the right light conditions is important; coffee plants thrive in bright, indirect light, so an east or west-facing window is often ideal.
Maintaining high humidity (ideally 50-60%) can be achieved through humidifiers, pebble trays, or regular misting. Regularly inspecting your coffee plant for early signs of pests or diseases allows for prompt intervention.