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Leaf scorch on trees: what extension services describe

Leaf scorch is brown, crisp leaf edges or patches. Extension services in Missouri, Utah and North Carolina describe weather and water as the usual cause, and a bacterial disease as one look-alike.

Checked against the sources at the bottom of this page on October 8, 2026. Rules, fees and pay change: the source has the last word.

This page describes what the named extension services and the Missouri Botanical Garden say. It does not diagnose a tree, say whether any tree is safe or unsafe, or tell anyone to treat, replace or remove one. The word scorch covers several different causes, and the sources keep them apart. Where they differ, the page says so.

What the sources call it

The Missouri Botanical Garden calls leaf scorch a widespread noninfectious disorder of any tree or shrub. It says scorch most often follows long spells of dry, windy weather or bright sun, when roots cannot supply water to the leaves as fast as the leaves lose it. Utah State University Extension calls it a general plant response to drought, underwatering, intense sun and heat, wind, soil compaction and nutrient deficiencies, and says it is most severe on ash, maple, pine, horse chestnut, elm and poplar.

A Utah State University Extension horticulturist (Ask an Expert, August 28, 2025) says that by August many Utah trees show brown, crispy leaf edges because low humidity and strong sun mean the tree cannot always move water to its leaves fast enough. It adds that moderate leaf drop, especially from the inner crown, is a common symptom, and that horse chestnut, maples, lindens, poplars and aspens are commonly affected.

What it looks like

Missouri lists browning of leaf margins, or yellowing or darkening between the main veins, with leaves that dry, turn brown and become brittle. It says to look for damage on the upper, sunny, southern side and the windy side, and that leaf drop and twig dieback can follow in late summer. On narrow-leaved evergreens it describes brown or purple-brown needle tips, and says that should not be confused with the normal browning and shedding of older interior needles. Winter scorch in evergreens, from dry winds while the ground is frozen, appears as two long brown areas alongside the main leaf vein, and Missouri says symptoms may not show for a month or more after the injury. Utah State describes necrotic leaf margins or areas between the veins, and says severe scorch can kill leaves.

Other things the sources link to scorch

Missouri says anything that stops a plant taking up water can produce scorch, including insect and disease problems, and it lists excess fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots, strangling wires, vehicle exhaust and heat reflected from buildings. It names sandy or gravelly soil, pavement or obstructions that limit roots, and exposed windy slopes as sites that favor scorch. Utah State says the main cause is a lack of water in the root zone combined with wind and sun, and that trees in restricted root zones or compacted soil are more exposed. The Utah horticulturist adds that scorch can come from iron, manganese and magnesium becoming less available in alkaline soil, which causes yellow leaves that scorch as the season goes on (see the page on iron chlorosis), and that overwatering a newly planted tree can rot roots and mimic drought stress.

Whether the sources call it harmful

The sources differ in emphasis. The Utah horticulturist describes late-summer scorch as often alarming to look at but usually not a threat to long-term health, and in most cases a seasonal cosmetic matter, provided the tree looks normal the following spring and the browning appears only late in the season. Missouri says that in mild cases leaves stay attached and little damage results, in severe cases many leaves may drop early without the plant dying, and that scorch recurring every year gradually weakens a plant and makes it more open to insects and disease. The Utah horticulturist also says not all scorch is harmless: it names fungal vascular wilt in maples, where branches fail to recover over several years, as a different problem with similar browning.

A bacterial look-alike

North Carolina State Extension (Scorch Diseases on Shade Trees, September 23, 2024) describes a separate disease, caused by fastidious bacteria that live only in a tree's water-carrying xylem cells and are carried between plants by sharpshooter leafhoppers. It reports the disease on elm, red maple, mulberry, sycamore, pin oak and southern and northern red oak. It says marginal browning or red discoloration starts in late July and early August, may first affect only part of the crown, grows worse each year as the bacteria spread, and is followed by dieback and decline, with epicormic sprouts common on declining trees. The Utah horticulturist puts the difficulty in one line: the key is knowing when scorch is temporary and when it points to a deeper problem. This page does not make that call for any tree.

The other pages in this group are listed on the weather, soil and chemical damage page. For how water moves through a tree, see how a tree works.

Sources