Leaf Burn and Leaf Scorch

Description
Leaf burn and leaf scorch occur when leaf cells overheat. Although the two terms are often used interchangeably, leaf scorch usually refers to browning and tissue death around leaf margins and between veins, while leaf burn usually refers to dead patches in the middle of the leaf. Normally, leaves are cooled by the evaporation of water from their surfaces. When leaves dry out, the amount of water that evaporates is reduced and they overheat, then burn or scorch. Sometimes entire leaves or shoots are damaged. Several different conditions may cause leaf burn or leaf scorch. Many of these factors are interrelated; when they occur in combination, damage may be severe.

Lack of water: Leaf burn and leaf scorch often occur when plant roots can't get enough water. Many soil conditions may cause dehydration. Plants growing in dry, salty, frozen, or restricted soil areas may not get as much water as they need.

Too much water: Overwatered or heavy, poorly drained soils can cause burn or scorch. Roots require oxygen to function properly. Wet soils are often low in oxygen, causing root death. As the roots start to die, they absorb less water.

Wind and heat: Hot, windy conditions cause burn and scorch in some plants, even when the soil is moist. Wind and heat cause water to evaporate more quickly from the leaves than it can be replaced.

Freezing damage: Leaf burn or leaf scorch may result when foliage freezes. Frozen leaf cells rupture or dry out and die.

Other factors: Roots that are diseased or mechanically damaged often cannot supply as much water as the plant needs, resulting in leaf burn or leaf scorch. Burn and scorch can also be caused by an accumulation of salt in the leaf tissue. (For more information, see Salt Damage.)

Control
Leaves damaged by leaf scorch or leaf burn will not recover. Keep plants properly watered to help reduce further damage. (For more information about proper watering, see About Watering.) If possible, shade plants during very hot weather, and hose down foliage a couple of times a day. (For more information about heat protection, see Heat Protection.) Make sure the soil is moist when it freezes, and reduce chances of dehydration resulting from frozen soils by applying a mulch around the base of the plant. (For more information about mulching, see Mulching.) Inspect damaged plants for root rot or mechanical damage. (For more information about root rots, see Water Molds.) Protect shade-loving plants by providing adequate shade.