Fig trees (Ficus carica) are widely cultivated for their fruit and aesthetic appeal. Despite their robust nature, these trees are susceptible to physiological damage known as sunburn, a common stressor for many woody plants. Sunburn occurs when intense solar radiation overwhelms the plant’s protective mechanisms, leading to tissue damage. This damage manifests as visible injury to the foliage and the delicate bark on the trunk, potentially impacting the tree’s overall health and fruit production.
Identifying Fig Sunburn Symptoms
Sunburn symptoms on fig leaves typically appear first as scorched or bleached areas on the leaf surface most directly exposed to the sun. Initially, these areas may look pale or whitish, indicating the destruction of chlorophyll within the cells. As the damage progresses, the tissue dries out, turning a brittle, papery brown, often concentrated along the margins or tips of the leaf blade.
Damage to the trunk is often observed on the south or west-facing side, which receives the most intense afternoon sun. This exposure causes the bark to heat excessively, leading to discoloration, frequently appearing as a reddish-brown or black lesion. Over time, the damaged bark can crack and split, creating entry points for pests or disease and exposing the vulnerable underlying cambium layer.
Primary Causes of Sunburn Damage
Sunburn damage is primarily triggered by a sudden increase in exposure to intense solar radiation, often following a period of cloudy weather or when potted trees are moved outdoors from a sheltered location. Heat spikes during summer also accelerate the damage, especially when combined with insufficient hydration. Light intensity can be significantly amplified by reflective surfaces nearby, such as white stucco walls, concrete patios, or pavement, which focus radiation onto the tree.
Sunburn is caused by the rapid heating of plant tissue and subsequent excessive water loss through transpiration. When the rate of water loss exceeds the tree’s ability to draw moisture up through its roots, the cells in the exposed leaves and bark desiccate. This rapid dehydration causes the collapse of cell structure, resulting in visible scorching and tissue death.
Treating Existing Sun Damage
When fig sunburn is identified, the immediate step is to provide relief from the intense solar exposure that caused the injury. For container trees, moving them to a location that receives afternoon shade is the fastest solution, or temporary shade cloth can be erected over in-ground trees. Deep, thorough watering is necessary to support the tree’s recovery and aid in establishing a healthy moisture gradient within the plant.
While the damaged leaf and bark tissue will not regenerate or heal, the tree will prioritize new growth once the environmental stress is mitigated. Severely scorched leaves can be selectively pruned if they are completely dead, but excessive removal should be avoided as slightly damaged leaves still contribute to photosynthesis. The recovery process focuses on encouraging the tree to produce healthy new foliage that is properly conditioned for the existing light levels.
Preventing Future Sunburn
The most effective proactive measure is the gradual process of acclimation, often called hardening off, especially for container figs moved outdoors in spring. This involves introducing the tree to increasing periods of direct sunlight over a period of two to three weeks. Starting with only an hour of morning sun and slowly extending exposure allows the plant to naturally build up protective pigments and thicken its cuticle layer.
Protecting the vulnerable bark is particularly important, especially in regions with intense winter or summer sun. Applying a mixture of diluted white latex paint and water, known as whitewashing, to the trunk reflects sunlight and significantly reduces the surface temperature of the bark. This protective layer should focus on the south and west sides of the trunk, where thermal stress is highest.
Proper site selection plays a significant role in long-term prevention. When planting a fig, choose a location that receives some filtered sun during the hottest part of the afternoon to minimize stress. Avoid planting trees immediately adjacent to highly reflective surfaces like bright walls or large expanses of concrete, which intensify solar radiation.