Why Are My Bougainvillea Leaves Turning Yellow?

Yellowing leaves on a bougainvillea are a sign the plant is reacting to its care or environment. Understanding the potential causes is the first step toward helping your plant return to health. This guide covers the most common reasons for yellow leaves and provides clear actions to remedy the situation.

Improper Watering

A primary reason for yellowing leaves on a bougainvillea is improper watering. Native to arid regions, these plants are sensitive to the moisture their roots receive. Overwatering is a frequent mistake that leads to limp, yellow leaves because excess water saturates the soil, cutting off oxygen to the roots and creating conditions for root rot.

To determine if you are overwatering, check the soil directly by inserting your finger about two inches deep. If the soil feels damp, wait longer before watering again. Bougainvillea thrive when the soil is allowed to dry out almost completely between waterings, which encourages strong root development and blooming.

Conversely, prolonged underwatering also causes leaves to turn yellow, though they will feel dry and crispy. During periods of extreme heat or if the plant is in a container, which dries out faster, you may need to monitor moisture levels more frequently. A consistent schedule that allows the soil to dry thoroughly before a deep soaking prevents both extremes.

Nutrient Deficiencies

The health of bougainvillea foliage is tied to the nutrients it absorbs from the soil. If leaves turn yellow while the veins remain green, the plant is experiencing chlorosis. This pattern indicates a nutrient deficiency where the plant cannot produce enough chlorophyll. For bougainvillea, this often points to a lack of micronutrients like iron or magnesium.

An iron deficiency appears first on new leaves at the branch tips. A magnesium deficiency presents on older leaves, creating a V-shaped yellowing pattern along the leaf margins. To address these issues, use a balanced fertilizer formulated for bougainvillea. These fertilizers contain the proper ratio of nitrogen, phosphorus, and potassium, along with necessary micronutrients.

Applying a specialized fertilizer during the growing season can correct these deficiencies. For a magnesium issue, supplementing with Epsom salts can be beneficial. Dissolve one tablespoon of Epsom salts in a gallon of water and use this solution to water the plant once a month. Always follow the application rates on any fertilizer to avoid chemical burns to the roots, which can cause further damage.

Environmental Stress

Bougainvillea can react to sudden environmental changes by shedding yellow leaves. Sunlight is a primary factor, as these plants require at least six hours of direct sunlight daily to flourish. If a plant is moved abruptly from a lower-light location to intense sun, its leaves can scorch and turn yellow as a stress response.

Temperature fluctuations can also trigger leaf drop. Bougainvillea are sensitive to cold drafts and sudden drops in temperature, and may shed yellow leaves when temperatures fall below 40°F. This can also occur when moving a potted plant indoors or outdoors without a gradual acclimation period.

Transplant shock is another stressor. When a bougainvillea is repotted or moved, it will experience an adjustment period. During this time, the plant diverts energy to establish its root system, which can reduce resources for foliage and cause some leaves to yellow and fall off as it adapts.

Pests and Diseases

Persistent yellowing may also indicate the presence of pests or disease. Sap-sucking insects are a common cause, as they feed on the plant’s juices, depriving leaves of nutrients and causing them to yellow and become distorted. Aphids often cluster on new growth and the undersides of leaves, leaving behind a sticky substance known as honeydew.

Spider mites are another pest that can cause damage, indicated by a stippled, yellowed appearance on the leaves and fine webbing on the plant. These pests thrive in hot, dry conditions. Inspecting your bougainvillea regularly can help you catch an infestation early, and management involves spraying the plant with water or using insecticidal soap for severe cases.

Yellowing can also be a symptom of root rot, a fungal disease resulting from overwatering. If the yellowing is accompanied by mushy stems near the soil line and a foul odor from the soil, root rot is the likely cause. At this stage, the plant’s root system is severely compromised, so ensuring proper drainage and careful watering is the best prevention.