The Chinese Evergreen, scientifically known as Aglaonema, is a widely favored houseplant celebrated for its striking foliage and relative hardiness. When the normally vibrant green or patterned leaves begin to turn yellow, a condition called chlorosis, it serves as the plant’s clearest signal of distress. Identifying the precise cause behind this yellowing is the first step toward restoring your plant’s health. This guide offers a systematic approach to diagnosing the problem and implementing the correct solution.
Diagnostic 1: Water and Soil Issues
Improper management of water is the most frequent reason a Chinese Evergreen develops yellow leaves. The symptoms of overwatering and underwatering, while both causing chlorosis, present differently and require distinct interventions. Overwatering leads to widespread yellowing, often starting with the lower leaves, where the tissue may feel soft or mushy.
When the soil remains saturated for too long, the roots are deprived of oxygen, leading to suffocation and the development of root rot. This fungal condition causes the roots to turn dark and mushy, preventing them from absorbing water and nutrients efficiently. To correct this, always ensure the pot has adequate drainage holes and use a well-aerated potting mix containing materials like perlite.
A simple inspection of the soil moisture is the best fix for both extremes of watering stress. Before watering, allow the top two inches of soil to dry out completely, which you can check by inserting a finger into the potting mix. Conversely, underwatering causes the leaves to become dry, crispy, and often brown at the edges before turning yellow. If the soil is bone dry, a thorough soak is necessary, allowing all excess water to drain completely.
Diagnostic 2: Light and Temperature Stress
Issues with light exposure can trigger chlorosis in Aglaonema, which naturally thrives in the dappled light beneath the canopy of tropical forests. When the plant receives insufficient light, the leaves may turn uniformly pale or yellow as the plant attempts to conserve energy. The solution is to move the plant to a brighter location with indirect light, such as near an east or north-facing window.
Conversely, exposure to harsh, direct sunlight can physically scorch the delicate leaf tissue. This damage appears as bleached, pale yellow, or brown patches on the leaves, which is a form of sunburn. The remedy involves relocating the plant to a spot where the light is filtered or less intense to prevent further damage.
Temperature stability is another environmental factor affecting the Chinese Evergreen, which prefers warm conditions between 65°F and 80°F. Exposure to cold temperatures, particularly below 60°F, can induce cold injury that manifests as sudden yellowing and leaf drop. Placing the plant near a cold, drafty window, an exterior door, or an air conditioning vent can cause this sudden stress. To prevent this, ensure the plant is situated in a stable, warm location away from any direct sources of cold air flow.
Diagnostic 3: Nutrition, Pests, and Aging
If water, soil, and environmental factors are optimal, the cause of yellowing may relate to the plant’s internal nutrition or external biological threats. Nutritional deficiencies usually appear as a generalized yellowing of the older, lower leaves as the plant translocates mobile nutrients like nitrogen to support new growth. A lack of micronutrients such as iron or magnesium can also cause chlorosis, sometimes presenting as yellowing edges with the veins remaining green.
To address these deficiencies, fertilize your Chinese Evergreen with a balanced houseplant fertilizer, typically at half-strength during the active growing season of spring and summer. Over-fertilization can lead to a buildup of mineral salts in the soil, which can burn the roots and cause leaf tips and edges to turn brown or yellow. Flushing the soil by slowly pouring a large volume of water through the pot, allowing it to drain fully, can help dissolve and remove excess salts.
Pest infestations are another cause of chlorosis, as sap-sucking insects like spider mites, mealybugs, and scale feed on the plant’s vital fluids. This feeding action depletes the leaf of nutrients and chlorophyll, often resulting in stippled, localized yellow spots or a general decline in leaf color. If pests are detected, treat the affected areas immediately by wiping the leaves with a cotton swab dipped in rubbing alcohol or applying a horticultural oil, like neem oil.
Finally, if only a few of the very lowest leaves are turning yellow and dropping off, this is likely a normal biological process called senescence, or natural aging. The plant recycles the nutrients from its oldest leaves to fuel new growth. This natural cycle is not a sign of distress and only requires the removal of the fully yellowed leaf.