Some species are better adapted to extreme heat, but sustained exposure to blazing sunlight can still take a toll on even the hardiest trees.
Hot Days, Stressed Trees Supporting Heat- and Drought-Stressed Trees Through Fall and Winter By Benjamin Culbreth
Summer’s long, hot and humid days can take a toll on tree health. And according to the latest data, those summer conditions are becoming more intense. Summer 2026 had the highest average tempera- tures on record, according to the National Centers for Environmental Information , and the season appears to be staying warmer for longer each year. August 2026 was also the hottest on record, with daytime highs reaching an average of 88.6°F. For trees, that means prolonged exposure to high temperatures and the potential for heat stress. While some species are more tolerant of extreme heat than others, prolonged exposure to blazing sun can damage even the hardiest trees. The effects of that stress do not necessarily disap- pear when temperatures begin to cool. As summer gives way to fall and eventually winter, trees shift into recovery mode. Caring for them during this transition is a balance of providing the support they need while also allowing them to respond to the damage on their own. UNDERSTANDING HOW HEAT AND DROUGHT STRESS HAPPEN Heat stress and drought stress may sound similar, and in many ways, the two are interconnected. How-
ever, understanding the distinction between them can help arborists identify what a tree is experienc- ing and how best to respond. Matthew Borden, doctor of plant medicine (DPM) and plant scientist specializing in research commu- nications at Bartlett Tree Experts , said warm tem- peratures themselves can play a significant role in damaging a tree. “It is the heat itself that’s breaking down processes and the plant’s physiology.” Those effects often begin where the tree is most directly exposed to the heat. Signs of heat stress typically appear in the outermost portions of the canopy. “On the average broadleaf tree, starting mid to late summer you’ll see parts of the leaf that face the af- ternoon sun turn yellowish.” While heat stress and drought stress are often discussed together, they are not interchangeable. There is an assumption that a plant that can tolerate less water will also be able to withstand heat well.
According to Borden, that is not always the case.
At the same time, the two types of stress can com-
ArborTIMES ™ Fall 2026 | 61
Made with FlippingBook - professional solution for displaying marketing and sales documents online