Tree Heat Stress Is Real: How to Protect Roots During Summer Heatwaves

Global temperatures have risen in recent years, leading to longer heat waves and drought periods that can negatively affect your trees. 

Heat waves can accelerate moisture loss and reduce oxygen levels in the soil, disrupting nutrient uptake and damaging the most vulnerable parts of the root zone, creating visible signs of distress in your trees. 

Protect your tree roots this summer by learning the signs of tree heat stress and what you can do to beat the heat. 

Key Signs of Heat Stress in Trees 

If left unchecked, heat stress can cause severe damage to your trees. Look out for these tree root stress symptoms: 

• Wilting or curled leaves during the day, even when watered 
• Early season leaf drop or thinning canopy 
• Cracked soil at the base of the tree
• “Scorched” leaf edges 

Regions Where Root Stress Risk Is Highest 

The U.S. is a vast country with significant differences in climate, depending on where you live. Heat stress isn’t as big a risk in areas of the country with cooler falls and winters, although those areas are still experiencing increased temperatures that affect tree growth. Here are the regions of the U.S. where root stress risk is highest: 

• Southeast – The combination of high humidity reducing transpiration and frequently compacted clay soils restricting airflow deprives roots of oxygen and the ability to grow deep to find water, leading to both heat and water stress.
• Southwest – Intense sunlight, low humidity, low annual precipitation, and saline/alkaline soils can cause root desiccation and drought injury to happen quickly. This is the region where heat and water stress are most intense, and trees are the most dependent on irrigation.
• Midwest – Temperature and precipitation have high variability, making the roots more susceptible to shock.
• West Coast – Conditions vary from the rainforests of the Pacific Northwest to the more arid, Mediterranean climates of the Southwest Coast, but the common theme is seasonal variability, with the highest rainfall occurring in fall and winter, followed by dry springs and summers. Tree roots will be stressed to find the necessary water during the dry seasons. https://blog.davey.com/how-to-reduce-heat-stress-on-seattle-trees/ 

Tips: How to Protect Tree Roots in a Heatwave 

Heatwave tree care doesn’t have to be complicated. Here are a few basic summer tree care tips that can help protect your roots in high temperatures: 

Mulching – Lay a 2- to 3-inch layer of organic mulch within the dripline to help insulate soil and retain moisture. Make sure to keep the mulch away from the trunk. 

Watering – Aim for slow, deep watering once or twice a week, focusing around the base of the tree and out to the dripline, making sure to get adequate water into the root balls of newly planted trees.  

Aeration – Aerate the soil and add organic matter, such as compost and biochar, to avoid compaction and allow for increased water and nutrient intake. Those materials also aid deeper penetration of air, allowing deeper rooting to access deep soil water.  

Inspecting – Inspect the root zone for soil compaction, moisture levels, decay, and disease, and have an arborist treat accordingly.  

Soil Testing – Test your soil for salt levels, pH, and nutrients, and fertilize as needed when cooler weather hits. Treat high salt levels by flushing with fresh water, using gypsum, and using organic compounds like humates and biochar.  

LEARN OTHER HEATWAVE TIPS & TRICKS FOR YOUR LANDSCAPE