Protecting Drought-Stressed Chicagoland Trees Before Winter Starts

The weather over the last few months has been perfect for enjoying the outdoors, but it has also negatively affected area trees—both deciduous and evergreen. In the Chicagoland area, drought conditions have returned, and watering is essential for tree health. There’s no substitute for water when it comes to enhancing plant growth, appearance and vigor, as well as reducing tree stress and the risk of insect and disease damage.  

Water stress inhibits the production and movement of essential materials in trees. With less carbohydrate production, proteins, enzymes and mineral nutrients are also affected. These deficiencies can lead to stunted growth and vitality, evident in symptoms such as chlorotic leaves, premature defoliation and bark splitting. Even when drought ends, trees struggle to recover, often requiring several years to regain full health. Growth reduction is typically most severe in the year following a drought.  

Drought-stressed trees become susceptible to pests and diseases, including borers, bark beetles and root disease fungi, which can accelerate decline and lead to death. Symptoms of moisture stress in broadleaf trees first appear on older leaves, presenting as wilting, browning leaf margins and early leaf drop. In conifers, older needles may wilt and turn brown, while new growth becomes stunted.

On average, a tree in the Chicagoland area requires about an inch of water per week during the growing season—approximately 750 gallons per 1,000 square feet beneath its canopy. In the 13 weeks prior to October, the region received only about 5.9 inches—less than half an inch per week. September had just 1.54 inches of rain, or less than 0.4 inches weekly.   

Trees have water reserves, but they are mostly empty, leading to the unfortunate sight of dead trees. Early fall leaf change, particularly if leaves turn brown, may indicate potential tree death rather than dormancy. Additionally, water acts as a natural lubricant in the branches and trunk, allowing them to bend without breaking. As trees dry out, broken limbs become increasingly common. However, it’s not too late to help our neighborhood trees, and sooner is better than later.Let’s revisit the basics of tree care: water, mulch and fertilization. 

Watering

Homeowners should ensure that their trees receive at least an inch of water weekly beneath the canopy during the growing season. New transplants, trees with root damage or those in sandy soil should be watered at least twice a week. For established trees in clay or loam soils, thoroughly watering once a week is sufficient. Drip irrigation systems or soaker hoses are effective, as they irrigate only the root zone and minimize runoff. Tensiometers are also useful for assessing irrigation needs. Trees do not have a magical mouth part at their base to “drink”. It is far more effective to water the root zone rather than allowing a hose to trickle at the base of the tree.  

Mulch

Mulch is vital for conserving soil moisture and reducing competition for water from weeds. It adds organic matter to the soil, promotes root development and improves moisture retention. Natural mulches, like wood chips, shredded bark and pine straw, are excellent choices. Apply mulch to a depth of 2 to 4 inches around landscape plants, but don’t exceed this depth around tree trunks, as it can be detrimental. Ideally, apply mulch to the tree’s “dripline”, but a narrow ring around the plant is better than no mulch. Remember: “Mulch like a donut, not like a volcano.” 

Fall Fertilization

Maintaining adequate soil fertility helps prevent nutrient stress and mitigate drought. Slow-release fertilizers are optimal for woody plants. Avoid agricultural fertilizers with high salt content, as they can exacerbate drought stress. For best results, base fertilization on soil analysis.  

Basic Tree Care Reminders

Drought stress periodically affects trees, with impacts varying by severity, duration and other factors like plant species, soil conditions, and existing disease or insect issues. A comprehensive plant healthcare program—including irrigation, mulching, fertilization, proper pruning and integrated pest management—is essential for helping landscape plants endure drought.

Homeowners should focus on water, mulch and fertilization. Regular inspections by a certified arborist from an accredited tree care company can help ensure that trees remain healthy and resilient.

M.D. Skeet (“Skeet”) is an ISA-certified arborist and commercial arborist representative in the Bolingbrook office of Bartlett Tree Experts. Bartlett has five offices serving Chicagoland, Wisconsin and Indiana, and more than 165 offices nationwide. For more information, call 630-960-4001 or visit Bartlett.com.

According to Bartlett Tree Experts, drought can cause significant damage to trees and shrubs, especially if it lasts for months or years. The following are some ways that drought can affect trees: 

Leaf and needle damage: The first signs of drought are often visible on the leaves or needles, manifesting as wilting, discoloration, browning or defoliation. 

Growth restriction: Drought can limit a plant’s ability to produce new shoots and foliage. 

Increased susceptibility to pests: Trees stressed by drought become more vulnerable to harmful insects and diseases, such as wood borers and root and stem diseases. 

Uprooting: Drought conditions can lead to uprooting, as the dry root systems are unable to anchor the tree securely in place. 

Several factors can influence how drought impacts a tree:

Species: Different species of trees may respond variably to drought conditions.

Soil conditions: The state of the soil can significantly affect a tree’s response to drought.

Duration of drought: The length of the drought period can influence the extent of damage inflicted on the tree. 

To help trees withstand drought, implement measures such as irrigation, mulching, fertilization, proper pruning and integrated pest management. 

Some tips for watering trees include:

• Watering during the night or late afternoon.

• Irrigating the root zone rather than the trunk.

• Using mulch to minimize water loss.

For more information, visit Bartlett.com