With temps routinely exceeding the 90-degree mark and rainforest-caliber humidity levels, summers in Central North Carolina can be miserable. But our hot-and-humid summers aren’t only challenging for people. They can also be hard on your trees — even our native species that have evolved to live here.
We’ll share a few of the most important ways our hot, damp summers can stress your trees and provide a few tips for helping your trees cope with the conditions below.
Five Ways Summer Heat and Humidity Stress Your Trees
There are a variety of summer stressors that can take a toll on your trees, but the following five are among the most important.
1. Trees Lose Water Faster
Soaring temperatures increase the rate of transpiration – the process by which water evaporates from pores in a tree’s leaves. So, even when rainfall is adequate, prolonged periods of high temperatures can cause trees to lose water faster than their roots can replace it. This leads to wilting, leaf scorch, and reduced vigor.
2. Saturated Soils Can Suffocate Roots
July and August are typically the wettest months for Central North Carolina. And because poorly drained, clay-rich soils are common in our area, tree roots often become deprived of oxygen, ultimately weakening the trees and increasing their susceptibility to decline.
3. Fungal Diseases Love Humidity
High humidity levels help support many harmful fungi, which can lead to an uptick in several foliar diseases, including leaf spots, mildews, blights, and anthracnose infections. Fungal outbreaks are especially common in trees that have overly dense canopies or are growing in areas with poor airflow.
4. High Summer Temperatures Challenge Newly Planted Trees
Trees take some time to establish healthy root systems following transplantation (especially when planted in compacted, clay-rich soils). When exposed to high temperatures, newly transplanted trees often become stressed by the heat and experience transplant shock.
5. Heat and Moisture Stress Attract Secondary Pests
Adding insult to injury, trees often suffer from secondary problems after they become stressed by high temperature and humidity levels. For example, stressed trees are often less capable of defending themselves against opportunistic insects and disease organisms.
Arborist Pro Tip: It’s important to note that healthy, mature, and established trees generally tolerate summer heat and humidity pretty well. The trees most vulnerable to summer stress are newly planted trees, recently transplanted trees, trees growing in compacted soils, and trees already weakened by pests or disease.
How to Protect Your Trees During Central NC’s Hottest & Wettest Months
Fortunately, there are several things you can do to help prepare your trees for high temperatures and damp conditions. A few of the best strategies include:
- Water your trees deeply during dry periods. Grass may benefit from frequent, shallow waterings, but trees prefer the opposite. This helps to encourage deep root development, which will further help support them through dry spells.
- Apply mulch over the root zone. Mulch helps moderate soil temperatures, protect roots from physical harm, and retain moisture. Just be sure to keep the mulch away from the tree’s trunk to prevent basal decay and keep the mulch depth appropriate — don’t add more than 2 to 4 inches.
- Avoid damaging roots during the summer. You should always try to protect your tree’s roots, but it’s especially important to do so during the summer. If possible, schedule construction projects, grading work, or trenching for the late fall or winter, when trees are dormant.
- Monitor your trees for signs of insects or disease. Many insect and disease problems are treatable, but you’ll give your trees the best chance of making a full recovery if you act quickly, before the problem becomes serious.
- Avoid unnecessary pruning during the summer. While you should always have hazardous branches removed promptly and without regard for the time of year, it’s better to avoid unnecessary pruning during the summer.
- Be especially careful with newly planted trees. Newly planted trees are often at greatest risk during hot and humid weather. That’s part of the reason it is typically wisest to plant trees in the fall, as they will have several months to develop robust root systems.
- Contact an ISA-certified arborist at the first sign of trouble. The most important thing you can do for your trees is to get expert help at the first sign of trouble. An ISA-certified arborist can diagnose the problem and recommend an appropriate solution for helping your trees.
Trees That Often Experience Summer Stress in Central North Carolina
Most healthy, established trees tolerate Central North Carolina summers quite well. However, some species are more prone to heat stress, leaf scorch, fungal diseases, or drought-related problems than others. These include:
- Flowering dogwoods (Cornus florida): These understory trees can struggle when planted in direct sun, and they are quite susceptible to anthracnose, powdery mildew, and other foliar diseases.
- Flowering cherries (Prunus spp.): Another group of trees that can suffer from fungal leaf diseases during humid weather, they frequently decline in compact or poorly drained soils.
- River birches (Betula nigra): Though they’re more heat tolerant than some other birches, river birches can suffer and begin shedding their leaves during extended droughts.
- White pines (Pinus strobus): Typically best-suited for slightly cool conditions, white pines may struggle from heat stress, drought stress, and several common diseases.
- Japanese maples (Acer palmatum): Another understory species that will often suffer when exposed to high temperatures or full sun, Japanese maples may develop leaf scorch during the summer.
Let Lubbers & Sons Tree Care Provide the Support Your Trees Need to Thrive
Whether your trees are suffering from heat stress, struggling with foliar fungi, or enduring an insect attack, the plant health care experts at Lubbers & Sons Tree Care can help. Contact us now to set up an evaluation and receive a free, itemized estimate for the services your trees need.
Sources & References
- South Dakota State University Extension – “Trees & Drought Stress”
This cooperative extension resource explains the transpiration process in trees, the role of water loss in leaf cooling, and how summer heat accelerates water demand beyond what root systems can supply — leading to leaf scorch, wilting, and premature leaf drop.
https://extension.sdstate.edu/trees-drought-stress - Tennessee State University Cooperative Extension – “Japanese Maple Production and Care”
This comprehensive agricultural extension guide details standard cultivation practices, propagation techniques, structural pruning, and disease prevention for managing Acer palmatum in nurseries and landscapes.
https://digitalscholarship.tnstate.edu/cgi/viewcontent.cgi?article=1117&context=extension - University of California Agriculture and Natural Resources – “Preventing Japanese Maple Sunburn”
This practical master gardener resource diagnoses the causes of leaf scorch and bark sunburn on sensitive maple varieties, offering strategic solutions like temporary shading and soil moisture regulation.
https://ucanr.edu/site/uc-master-gardeners-placer-county/article/preventing-japanese-maple-sunburn - International Society of Arboriculture (ISA) – “Proper Mulching Techniques”
This official educational brochure outlines correct mulch application depth and ring diameter, highlighting how bad habits like “mulch volcanoes” suffocate root systems and cause decay.
https://www.treesaregood.org/Portals/0/TreesAreGood_Proper%20Mulch%20Tech_0321.pdf
