Water trees wisely to beat winter woes

URBANA, Ill. — As autumn colors emerge, it may seem that trees are preparing for rest. However, when fall brings dry conditions instead of seasonal rains, trees can enter winter under stress. Fall droughts can be subtle but have lasting impacts. With timely care, trees can weather dry spells and head into winter strong.

Moisture Matters in Fall

Even after leaves drop, tree roots remain active well into late fall. This period is critical for absorbing and storing water before the ground freezes. Without sufficient moisture, trees may experience root damage, reduced cold hardiness, and increased susceptibility to pests and diseases in spring.

Trees that are young or newly planted, as well as shallow-rooted species like maple and birch, are particularly prone to water stress. During a fall drought, their limited root depth relies on surface soil moisture that depletes quickly.

Evergreens are also vulnerable, as they continue to lose moisture through their needles during winter. Entering dormancy in a dry state increases the risk of winter burn and dieback.

Soak Smarter, Not Harder

Fall watering should focus on depth rather than frequency, which is highly variable among climates, soil types, and tree species. Some young trees may require water every week, and newly planted trees may require more often than that. Mature trees benefit from a less frequent, deep soak when rainfall is insufficient. 

The goal is to moisten the soil 8 to 12 inches deep beneath the canopy, where most absorbing roots are located. Soaker hoses, drip irrigation, or a slow trickle from a hose are effective methods to ensure moisture reaches the root zone without runoff. Water the roots of large trees just outside the dripline, not at the trunk.

Watering is recommended when:

• Soil is dry 4 to 6 inches below the surface
• Air temperatures remain above 40 F
• The ground is not yet frozen

Maximize Moisture with Mulch

A 2 to 4-inch layer of organic mulch, such as arborist wood chips, retains soil moisture and reduces competition from turfgrass. Mulch should extend to the drip line if possible and be kept a few inches away from the trunk to prevent rot. Mulching not only conserves water but also insulates roots from sudden temperature fluctuations as winter approaches.

Save the Fertilizer for Spring

Fertilizer should be avoided in the fall, particularly during drought. Late-season fertilization can stimulate new growth that is vulnerable to frost damage. Instead, efforts should focus on hydration and root health to support long-term resilience.

Scan for Stress

Signs of drought stress may include early fall coloration, leaf scorch, or premature leaf drop. In evergreens, browning at needle tips or needle loss may occur. These symptoms can also indicate pest or disease issues, which are more likely to affect stressed trees.

Proper care during drought is an investment in long-term tree health. Prioritize evergreens and young trees, especially those planted within the past two years. With consistent care during dry autumns, trees are better equipped to withstand winter and flourish in the growing season ahead.

For more on tree health, check out University of Illinois Extension’s downloadable Tree Care Basics fact sheets, including Tree Maintenance Schedule, Proper Mulching Techniques, Care of Newly Planted Trees, and Dormant Season Tree and Shrub Pruning. 

For questions, connect with a local University of Illinois Extension office from the statewide map.

Caption: Tulip poplar (Liriodendron tulipifera) showing early fall color, symptomatic of drought stress. Photo Credit: Brian Kunkel, University of Delaware via Bugwood.org #5429895.

SOURCE/WRITER: Sarah Vogel, horticulture educator, Illinois Extension

EDITOR: Jenna Braasch, media communications coordinator, Illinois Extension