August 28, 2026, 4:16 am | Read time: 4 minutes
When the lawn becomes crispy, the entire garden is stressed, including the trees. Gardening expert Katharina Petzholdt explains how to recognize heat damage in trees and how to help.
The leaves droop, turn brown prematurely, and fall off. Hot days take a toll on trees, especially when heatwaves last longer. The climate crisis is causing this to happen more frequently, even in home gardens. However, high temperatures alone are usually not the main problem. Heat damage to trees primarily results from the dryness that accompanies the heat. When trees no longer have enough water, they pull the emergency brake and close the stomata in their leaves. This conserves moisture but also stops carbon dioxide intake–the tree protects itself from drying out but begins to starve.
Signs of Heat and Drought Stress
Initially, leaves often curl during the day and only open again in the evening. If the dryness persists too long, many trees take on an autumnal appearance. The leaves turn yellow or brown prematurely and fall off. Trees also shed fruits–from acorns to apples–before they ripen. They discard anything they can no longer sustain. If the dryness continues, crown and root damage may occur, sometimes becoming visible weeks after the actual heat period. Even fully leafed, healthy-looking branches can unexpectedly break due to severe drought stress.
Trees can also get sunburned. It usually occurs on the south or southwest side of the trunk. Typical signs include discolored bark areas, splitting bark, or sunken spots on the trunk. Since these damages sometimes appear with a delay, clear attribution is not always easy. Leaves and fruits can also be affected by sunburn. Leaves develop light spots and often a papery texture. Fruits develop light, soft, sometimes sunken spots on the sunny side. Trees that are suddenly exposed–such as after a neighboring tree is felled–are particularly at risk.
Also interesting: How sponge gardens regulate water supply for your plants
Which Trees Are Particularly at Risk
Heat and drought particularly affect young trees. Their roots have not yet reached the deeper, moister soil layers that older specimens can access even during extended dry spells. However, the advantage of older trees is no guarantee: If the drought lasts too long, even established trees reach their limits.
Large-leaved species like sycamore or summer linden evaporate a lot of water through their large leaf surface, quickly depleting soil reserves. They experience stress sooner than more frugal trees. These include field maple, hornbeam, cornelian cherry, or serviceberry: They cope better with limited water reserves and are increasingly considered alternatives for new plantings.
5 Reasons Why Plants in the Garden Don’t Survive Winter
These 6 Care Mistakes Make Plants Suffer Even More in Heat
Can Trees Recover from Heat and Drought Stress?
Affected trees can usually recover fairly quickly if enough water is supplied in time. Even drooping leaves often perk up again within a few days. It becomes more challenging with crown and root damage: They do not heal completely but are gradually compensated over several years, not in a single season. A tree that has suffered severe drought stress once remains more susceptible to pests and fungi, which can more easily infest weakened trees.
What Garden Owners Can Do During Heatwaves
The most important rule during hot and dry phases: Water! And not a little every day, but less frequently and more thoroughly. “Thoroughly” is much more than hobby gardeners often assume. A rough guideline is 50 to 100 liters of water per watering for younger trees, about once a week during prolonged dryness. To prevent the water from simply running off the surface, it needs time to soak in. A raised earth wall around the tree or special watering bags that release water to the ground over hours can help. Older, larger trees need significantly more. Since their fine roots, which absorb nutrients and water, often lie in the outer crown area, the water should preferably be applied there.
Mulching is also a good way to support trees in their water management. A layer of mulch retains moisture in the soil and simultaneously shields it from external heat.
A white coating on the trunk is no longer just winter protection. In summer, the white color reflects intense sunlight, lowers the bark’s temperature, and can help prevent cracks through which pathogens could later enter.
Preventively, it also helps to consider heat and drought tolerance when choosing tree varieties from the outset.