Garden Gossip with Lori Bowling

Garden Gossip

With Lori Bowling

(Retired) University of Kentucky Extension Agent

Leaf Scorch on Landscape Plants

The Ashland Beacon

As the summer months move toward fall, some of your landscape trees, shrubs, and perennials may start to show browning along their leaf edges, as if they have been scorched by the heat of a fire. This condition is known as leaf scorch, and while it is not an infectious disease, it can cause your landscape to look unhealthy. We usually see this condition following a dry period, windy weather, bright sunshine, or extremely high temperatures. What happens is that the plant's roots are not able to supply enough water to the foliage because it is losing moisture rapidly through transpiration from its leaves. Leaf scorch can also be caused by excessive fertilizer, deicing salt, girdling roots, gas line leaks, damage to the trunk or roots, vehicle exhaust, and heat reflected from buildings.

Locations or conditions that can promote leaf scorch include sandy soil, soil with a high gravel content, plants growing near pavement or in areas that restrict root growth, and windy slopes. Other factors that affect a plant's ability to take up water and can lead to leaf scorch include disease, insect damage, or accidental herbicide or pesticide drift.

A mild case of leaf scorch causes the leaves to brown around the edges, but they remain attached to the plant. In severe cases, leaf scorch can result in premature leaf drop and possible twig dieback. While severe leaf scorch will not usually kill a plant, if it occurs annually on the same plant, it can gradually weaken it, making it more susceptible to insects and diseases.

To combat leaf scorch, you should water plants during dry periods. A good rule of thumb is that plants need about 1 inch of rainfall or supplemental water per week. After watering, the soil should be moist to a depth of 10 to 12 inches. Regular fertilization based on soil test results can also help keep a plant healthy. Fertilize in the spring, but if you make a fall application, be sure it contains little to no nitrogen. Too much nitrogen applied in the fall can encourage new, tender growth that will not have time to harden off before cold weather, making it more susceptible to winter injury. Mulching around plants is also beneficial because it helps retain soil moisture and keeps the soil cool during the hot summer months. No more than 2 to 3 inches of mulch should be applied to ensure that water can easily reach the soil.

Because leaf scorch can result from insect or disease damage, it is a good idea to carefully inspect the entire plant to determine if there are other problems that may be causing the symptoms. If you suspect another issue is contributing to the leaf scorch, contact your local county Extension office for assistance in determining the cause and the best way to address the problem.