The difference between a tree that bounces back quickly and one that struggles for years often comes down to recognizing the signs of drought stress before they become permanent damage.
Pay attention to these two things: wilted foliage and yellow or scorched leaves in the canopy or on the ground. These are the early signs of drought stress in trees and your cue to water their root area. Dry branches, cracked bark, and mushrooms show more serious damage, so consider bringing on a certified arborist. We tell you all the signs to watch for and what to do in this article.
Early Warning Signs of Drought Stress
What is drought stress for trees? Drought stress appears when the water in the soil is so low the tree roots can’t absorb enough moisture and start drying and dying.
First, the fine hair-like roots die; then the thicker, fibrous ones. This root damage stresses the entire tree, reducing its ability to function, grow, and protect itself from diseases and pests. The key thing to remember is that the leaves are first to show signs of stress.
Note: Not sure what is wrong with your trees? Call a tree care professional for a thorough check up and treatment.
Changes in the Tree’s Foliage
Around 95% of the water a tree absorbs from the soil travels to the leaves where it evaporates due to wind and heat. When the soil lacks water, leaves are the first to feel the stress and show it:
- Leaves wilting and drooping: At this stage, leaves wilt during the day but recover during the night.
- Leaf discoloration: The green color fades then turns yellow or brown. In high heat, leaves look scorched. Conifer needles turn brown from the tip.
- Leaf curling or rolling: Leaves curl or roll inward to reduce the sun-exposed surface and limit water loss.
- Leaf shedding: If curling is not enough to save water, trees start shedding their leaves. Old leaves and those in full sun (top of the crown and end of branches) fall first.
- Leaf size reduction: New leaves grow smaller as the tree conserves water and energy for vital functions.
Some trees are more vulnerable to drought than others. Pay attention to young and newly planted trees, water-loving trees, and trees planted in sandy or compacted soil or directly exposed to the afternoon sun.
Growth and Development Problems
With less water and damaged leaves, the tree can’t produce enough energy and food to grow properly, leading to signs such as:
- Stunted growth: Trees under drought stress are smaller in size and have thinner branches and smaller leaves.
- Early bud set: Forming buds earlier is a sign the tree is preparing to enter dormancy to survive the stress period.
Note: The negative effects on tree growth are often long term. According to the Texas A&M Forest Service, root, trunk, and shoot growth can be affected for 2 to 3 years after the drought has subsided.
Environmental Signs of Drought Stress
When they don’t receive enough water, trees try to pull more moisture from the soil surrounding them. Here’s what to watch for:
- Exceptionally dry soil
- Cracked soil
- Soil pulled away from the trunk
Advanced Signs of Severe Drought Stress
When you miss the early signs and the tree is exposed to prolonged drought-stress, it can suffer severe damage and even die. In fact, the Texas A&M Forest Service estimates the 2011 drought killed 6.2% (300 million) of the state’s trees, demonstrating just how devastating drought stress can be.
To catch severe drought damage before it reaches a critical point, examine your trees for these warning signs:
Visible Canopy and Leaf Damage
Exposed to prolonged stress, trees keep shedding their leaves to conserve water and energy. In your tree’s canopy this is visible as:
- Permanent wilting: Leaves don’t recover during the night (unless you water the tree).
- Thinning canopy: Leaves keep falling for a few weeks, and you can easily see through the tree’s sparse foliage.
- Premature leaf drop: Most of the leaves have fallen, and your tree is almost empty.
Note: Evergreen trees are the most sensitive to severe leaf damage because they can’t regenerate their foliage as well as deciduous trees.
Structural Tree Damage
Structural damage is what makes trees more likely to fall during a drought. It affects the roots, trunk, and branches, weakening wind-resistant trees and making them more susceptible to breaking and uprooting in windstorms.
- Branch dieback: Branches dry out throughout the tree canopy, starting from the top.
- Bark cracks and peeling: If the bark cracks vertically and peels-off, it means it’s overly dry. Thin-barked trees like maples are the first affected.
- Surface root exposure: Roots appear on the soil surface through soil cracks or break out of compacted soil to look for oxygen.
Excessive Seed Production
Trees with severe drought damage produce cones, seedheads, or suckers earlier in the season or in an excessive amount in an effort to reproduce.
Pests and Diseases
Trees use their sap to fight against pests and diseases, but during prolonged drought the sap is either not enough or the bark is cracked and sap can’t travel properly. This vulnerability leads to:
- Increased pest activity: Watch for spider mites and boring insects such as bark beetles, ips beetles, and flathead borers.
- Fungal diseases: You might see mushrooms and other forms of fungal growth under loose bark, on the tree’s lower trunk and roots. Common types of tree fungus such as Phytophthora root rot and Verticillium wilt thrive when trees are stressed.
- Canker diseases: Look for sunken areas on bark. These are bacterial or viral infections on small wounds that the drought-stressed tree is unable to close. Hypoxylon canker is a common disease in oaks.
In 2018, bark beetles killed 18 million of California’s trees that were too weakened by a six-year drought to defend themselves. Given the potential for severe damage, consider these signs as time-sensitive warnings, and reach out to a certified arborist for professional treatment.
See Related:
- Maple Tree Diseases and How to Treat Them
- Pine Tree Diseases and How to Treat Them
- Apple Tree Diseases and How to Treat Them
When to Call a Professional vs. DIY Treatment
DIY treatment works well when: You notice early signs like leaf wilting, slight discoloration, or small areas of leaf drop. Deep watering and mulching can usually resolve the issue and are the keys to tree care during drought.
Call a certified arborist when: You see cracks in the bark, significant branch dieback, pest infestations, or more than 50% leaf loss. Professional treatment may include a specialized watering system, pest management, and structural assessment.
Cost considerations: An arborist consultation typically costs $75 to $250 per hour while tree removal costs between $385 to $1,070. Planting a new tree costs between $150 and $1,850.
Read More:
- What is Drought-Tolerant Landscaping?
- 7 Benefits of Xeriscaping
- Top 10 Drought-Tolerant Grasses for Your Yard
FAQ
It depends on the damage and the tree. Some trees recover even after shedding all their leaves; others don’t manage to harden off enough to survive the next winter, and die.
Heat stress damages leaves directly, while drought stress kills the roots first and then affects the entire tree. When combined, they lead to severe damage and can kill the tree.
Some of the most drought-resistant trees in the U.S. are Eastern redbud, common hackberry, bigleaf maple, Kentucky coffeetree, and bur oak.
Early symptoms like leaf wilting can happen after a few weeks of drought, while more severe symptoms such as leaf yellowing, bark cracking, or branches drying take months or years.
Fight Drought Stress with Professional Tree Care
It takes years to grow a tall, beautiful tree that can be compromised by drought in a single season. Find a tree care professional with LawnStarter and ensure your valuable trees have the best care and protection against drought and damage.
Sources:
- “18 Million Trees Died in California in 2018.” By Alexa Lardieri, staff writer. U.S. News.
- “Don’t Give Up on Drought-Stressed Trees.” By Bert Cregg, professor in the Department of Horticulture. Michigan State University.
- “Drought Stress in Trees.” By Keith O’Herrin, urban forester for Union County. North Carolina Urban Forest Council.
- “Effects of Long-Term Drought on Landscape Trees.” By Jason S. Gordon, former associate extension professor of forestry. Mississippi State University Extension.
- “Forest Health Highlights 2012.” Texas Forest Service.
- “Watering Trees in Hot, Dry Home Landscapes.” By Heidi A. Kratsch, sustainable horticulture specialist. University of Nevada, Reno Extension.
Main Image Credit: Brian Kunkel / University of Delaware / Bugwood.org
