Leaf Burn & Leaf Scorch
Leaf burn and leaf scorch are terms generally used to decribe damage to vegetation caused when the cells of the leaf tissue become overheated. Leaf burn (top photo) specifically refers to damaged tissue in the cetral region of the leaf, while leaf scorch (bottom photo) refers to damage to the tissue at the edges of the leaf and between the veins. Damaged tissue is dead, and cannot be repaired.
Leaves are normally cooled by the evaporation of water which transpires from the leaf. Several conditions can affect the leaves' ability to transpire moisture at a normal rate. Any of these conditions can result in leaf burn or leaf scorch. When these conditions occur in conjunction, damage can be severe.
Underwatering: Lack of available water to the plant's root system will deprive the leaves of the water necessary to remain cool and healthy. Condition can be caused by soil drought, frozen soil, salty soil, or restricted root system.
Overwatering: Poorly drained soil, or soils that are not allowed to dry adequately between waterings can lead to leaf burn and leaf scorch because oversaturated soils deprive plant roots of oxygen. The root systems of many plants require oxygen to function properly. Chronic oxygen deprivation will cause the root fibers to die, preventing the plant from being able to take in sufficient moisture for the leaves.
Heat, humidity and wind: High temperatures, low humidity, and high winds can cause the evaporation of moisture from leaves faster than the moisture can be replenished, resulting in the drying and burning of leaves.
High humidity: High humidity can impede or prevent the evaporation of moisture from the leaf. Coupled with high ambient temperatures, leaf tissue can overheat, resulting in leaf burn or leaf scorch.
Mechanical damage: Damage to root systems from heavy equipment traversing the root zone, or damage to the tree bark from cables, chains, lawn maintenance equipment, or other contact damage can impede the plant's ability to deliver water to the leaves.
Improper placement of plants: Understory plants which are not shaded from direct sunlight can suffer leaf burn or leaf scorch because the plant's characteristics do not allow for adequate cooling in direct sun conditions.
Leaf burn and leaf scorch damage cannot be repaired. The condition(s) which caused the problem should be corrected to the extent possible. Severely damaged leaves should be removed. Less damaged leaves can be removed after refoliation occurs. A professional arborist can assist in determining the cause, and effecting a remedy for the condition.