Weather, soil and chemical damage to trees: what extension services describe
Some tree injuries come from sun, cold, water, salt, lightning or chemicals rather than from a pest. This page compares the problems that extension services and the Missouri Botanical Garden describe, one page each.
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 say. It does not diagnose a tree, say whether any tree is safe or unsafe, or tell anyone what to do about an injury. Extension services call injuries from weather, soil and chemicals abiotic: they have a non-living cause, unlike pests and diseases. The University of Arkansas System Division of Agriculture calls sunscald a physiological problem for that reason, with one cause behind both its summer and winter forms: death of bark tissue from damaging temperatures.
Compared at a glance
| Problem | What the sources describe | Where on the tree they place it |
|---|---|---|
| Sunscald | Dead or discolored bark and cambium, sloughing bark, sometimes a long vertical fissure. Arkansas names summer and winter forms. Utah and South Dakota describe the winter form. See the page on sunscald. | Lower trunk, south or southwest side (Arkansas, Utah, South Dakota) |
| Frost cracks | Deep vertical splits on the lower trunk. South Dakota says the origin is a trunk wound, Delaware and Arkansas point to temperature swings. See the page on frost cracks. | Lower trunk, southwest (South Dakota) or south-facing (Delaware) |
| Drought stress | Wilting, scorched edges, early color and leaf drop. Missouri and Utah say the symptoms resemble overwatering and salt damage. See the page on drought stress. | Whole crown; leaves first |
| Leaf scorch | Brown, crisp leaf margins or patches, tied to hot, dry, windy weather. North Carolina describes a bacterial disease with similar browning. See the page on leaf scorch. | Upper crown, sunny south and windy sides (Missouri) |
| Road salt | Browned or flecked foliage and dieback from spray, runoff or dust. Colorado reports damage within 20 feet of an unpaved road treated with magnesium chloride. See the page on road salt. | Side facing the road (Colorado) |
| Flooding and waterlogged soil | Yellowing, leaf drop, dieback and epicormic sprouts when roots lose oxygen. Iowa says most trees escape injury if water recedes within seven days. See the page on flooding. | Roots, then crown |
| Iron chlorosis | Yellow leaves with green veins on new growth, tied to high-pH soil that locks up iron. See the page on iron chlorosis. | New growth; often one branch or one half of the crown (Colorado, Utah) |
| Herbicide injury | Curled, cupped, twisted or burned foliage and dieback after drift, vapor or root uptake. No product or rate is named on the page. See the page on herbicide injury. | New growth, often several kinds of plant at once |
| Lightning | A strip of bark blown off, a split trunk, or no outside mark at all. Maryland and Missouri say the full damage can take a growing season or longer to show. See the page on lightning damage. | Trunk, top to bottom; roots (South Dakota) |
What the sun and winter sources share
All four sources tie these injuries to the daily swing between sun-warmed bark and a cold night. Utah State University Extension reports research finding the south side of a tree up to 77°F warmer than the north side on a cold winter day. South Dakota says the southwest side of a trunk can swing 30 to 50°F or more between a sunny winter day and a clear evening. Delaware and Utah name thin-barked trees such as maple and cherry as more prone, and young trees more than old ones.
Moisture is where they differ. Utah and South Dakota link drought stress to more injury, while Arkansas says a link between water stress and sunscald has never been confirmed by research. Each page in this family sets out the views side by side.
Other injuries not covered here
Damage from construction, grade changes and soil compaction is covered in the guide on trees and construction. How bark, cambium and the water-carrying tissues work is in how a tree works. Weed-killer injury touches pesticide rules; who may apply pesticides is in the guide to pesticide licences.
Problems, one page each
Sources
- University of Arkansas System Division of Agriculture, Sunscald on Trees (FSA6152), 2019, read October 8, 2026
- Utah State University Extension, Sunscald Injury or Southwest Winter Injury on Deciduous Trees (Forest Facts 021), 2011, read October 8, 2026
- South Dakota Department of Agriculture and SDSU Extension, Pest Update December 2-9, 2015, read October 8, 2026
- University of Delaware Cooperative Extension, Winter Injury and Frost Cracking, February 2026, read October 8, 2026
- Missouri Botanical Garden, Drought and Water Stress (environmental problems), updated 10/2024, read October 8, 2026
- Colorado State University Extension, Magnesium Chloride Toxicity in Trees, read October 8, 2026
- Iowa State University Extension and Outreach, Effects of Flooding on Trees & Shrubs, reviewed June 2024, read October 8, 2026
- University of Maryland Extension, Lightning Damage, updated March 1, 2023, read October 8, 2026
- NC State Extension, Scorch Diseases on Shade Trees, September 23, 2024, read October 8, 2026