Cilantro, a popular herb, often browns. Discoloration signals underlying problems. Understanding these causes is the first step to addressing them.
Natural Lifecycle and Bolting
Cilantro is an annual plant, completing its life cycle within one season. Bolting, a natural part of this cycle, involves the plant sending up a flower stalk and producing seeds, redirecting energy from leaves to reproduction, causing foliage to yellow or brown.
Temperature and day length trigger bolting. Cilantro prefers cooler weather (50°F-70°F / 10°C-21°C). Temperatures above this range, or longer days, signal accelerated reproduction. This browning indicates the end of its leafy harvest.
Watering Problems
Both insufficient and excessive watering cause cilantro leaves to brown. Under-watering stresses the plant, causing dehydration and crispy, brown foliage. Stems may lose stiffness, and the plant can wilt.
Overwatering is equally damaging, leading to waterlogged soil and root rot. Deprived of oxygen, rotting roots cannot absorb water and nutrients, causing leaves to wilt, brown, and die. Check soil moisture by inserting a finger an inch deep before watering; soil should be moist but not soggy.
Environmental Stressors
Cilantro thrives in specific environmental conditions; deviations cause stress and browning. Inadequate light, from too little to too much direct sun, causes leaf discoloration. Cilantro needs about six hours of direct sunlight, but in hot climates, afternoon shade prevents wilting and browning from excessive heat. Insufficient light reduces leaf size and plant vigor.
Extreme temperatures are another stressor. Cilantro struggles in high heat (above 80°F / 26°C), which can dehydrate the plant and trigger premature bolting and browning. Cold temperatures can also damage foliage. Maintaining temperatures between 50°F and 85°F is ideal for healthy growth.
Nutrient Imbalances
Nutrient imbalances (deficiencies and excesses) cause browning cilantro leaves. Lack of essential nutrients like nitrogen, phosphorus, or potassium causes wilting, yellowing, and browning. Nitrogen deficiency often leads to yellowing leaves.
Too much fertilizer, especially excess nitrogen, can burn the plant and result in brown leaves. Soil pH also affects nutrient absorption. Cilantro prefers slightly acidic to neutral soil with a pH between 6.2 and 6.8. If pH is too high or low, nutrient uptake is hindered, leading to browning.
Pests and Diseases
Pests and diseases weaken cilantro plants, causing leaves to brown or discolor. Common pests like aphids, spider mites, and whiteflies feed on plant sap, stunting growth and causing foliage to yellow or brown. Aphids multiply rapidly, causing significant damage if not addressed.
Cilantro is susceptible to bacterial and fungal diseases. Bacterial leaf spot, caused by Pseudomonas syringae, presents as water-soaked lesions that turn tan, brown, or black. Fungal issues like powdery mildew appear as white, powdery patches that may lead to browning in crowded or moist conditions. Damping-off, another fungal disease, attacks seedlings, causing them to wilt and rot at the soil line.
Preventing and Addressing Brown Cilantro
Proper watering is important to prevent browning and promote healthy growth. Ensure soil is consistently moist but never waterlogged; allow the top inch or two to dry before watering. Well-draining soil and containers with drainage holes help prevent root rot. Watering at the base, rather than from above, reduces fungal disease risk.
Managing environmental factors is important. Provide cilantro full sun (at least 6 hours) in cooler climates, but offer afternoon shade in hot regions to protect against intense heat and delay bolting. Maintaining moderate temperatures, between 50°F and 85°F, helps prevent heat stress. Applying organic mulch around plants helps retain soil moisture and keep roots cool.
For nutrient balance, cilantro thrives in nutrient-rich, well-draining soil (pH 6.2-6.8). Amend soil with compost or organic matter. If nutrient deficiencies are suspected, use a balanced organic fertilizer or dilute fish emulsion, but avoid over-fertilizing.
Regularly inspect plants for pests and diseases for early intervention. Hand-picking larger pests, using insecticidal soap for smaller ones, and ensuring good air circulation mitigate issues. Harvesting outer leaves regularly prolongs leaf production and encourages bushier growth.