Sunscald on Plumeria: What is Sunscald and what causes it?

Sunscald is a form of plant injury that occurs when leaf tissues are exposed to intense, direct sunlight for prolonged periods. While many assume tropical plants like plumerias are impervious to such sun damage, the truth is they can suffer from sunscald under extreme conditions. Here’s a more in-depth look at this phenomenon.

What Causes Sunscald?

1. Sudden Exposure to Sunlight: Plants that are moved from a shaded area to direct, intense sunlight without gradual acclimatization can experience sunscald. This is because their leaves have not developed the protective mechanisms to deal with the sudden influx of light energy.
2. High Temperatures: Sunscald is more common during peak summer days when the sun is most intense and the temperatures are high. This is especially true in locations that experience extreme seasonal variations.
3. Reflective Surfaces: Nearby surfaces like walls, patios, or even light-colored gravel can reflect sunlight, amplifying its intensity and increasing the risk of sunscald.
4. Water Droplets: While somewhat controversial, there’s a belief that water droplets left on leaves can act as tiny magnifying glasses, focusing the sunlight and causing small areas of scald. However, the scientific consensus on this is not entirely settled.

Identifying Sunscald

1. Color Changes: The most obvious sign is the change in leaf color. The affected areas often turn white, yellow, or brown, contrasting sharply with the healthy green surrounding tissues.
2. Texture Changes: Sunscalded areas may feel dry and papery and might eventually crack, exposing the internal tissues.
3. Location: Sunscald usually affects the most exposed areas of the plant, often the top of the leaves and sometimes the sides of fruits or stems.

How to Prevent Sunscald on Plumerias

1. Gradual Acclimatization: If a plumeria has been in a shaded area or indoors, it’s essential to gradually expose it to direct sunlight to allow it time to acclimate.
2. Provide Partial Shade: During peak sunlight hours, provide some form of shade, like shade cloths or even temporary structures like umbrellas.
3. Optimal Planting Location: Position your plumeria where it will receive morning sun and afternoon shade if the sun is extremely intense in your area.
4. Watering Practices: Watering should ideally be done early in the morning or late in the afternoon to avoid the heat of the day. Try to water the soil directly, avoiding the leaves.
5. Monitor and Adjust: Regularly inspect your plumerias for signs of sunscald. If you notice any, consider moving potted plants to less exposed areas or increasing the shade for those planted in the ground.

Treatment

1. Prune Damaged Areas: Remove damaged leaves or sections to prevent secondary infections and redirect the plant’s energy to healthier tissues.
2. Hydration: Keep the plant well-watered but not waterlogged, to help it recover from the stress.
3. Nutritional Support: Ensuring that the plant has all the nutrients it needs can help it recover more rapidly from stress conditions like sunscald.

Understanding sunscald is vital for anyone passionate about plumerias, particularly in regions with intense sunlight. Proper care and constant monitoring can go a long way in preventing this condition and keeping your plumerias healthy and vibrant.