By Blake Jackson
Fallen leaves are a familiar sight during autumn but leaving them on the lawn throughout winter can affect grass health and spring growth.
According to Bruce Spangenberg, a horticulture outreach specialist with the University of Wisconsin–Madison Division of Extension, homeowners can manage fallen leaves by raking them, composting them, or using them as mulch around gardens and landscape beds.
However, research suggests that the amount and condition of leaves left on lawns are important factors in preventing winter damage.
One potential concern is snow mold, a fungal disease that can develop under wet, cold conditions. The disease often becomes noticeable in early spring as matted, crusty patches across the lawn.
Although these areas may improve as the weather becomes warmer and drier, affected grass can remain weak or die. Reducing excessive fall nitrogen fertilizer applications and clearing heavy accumulations of leaves and other debris can help lower the risk of winter lawn damage.
Leaves can also suffocate grass when they accumulate in thick layers. Scattered leaves that are shredded during regular mowing generally break down naturally, adding organic matter to the soil.
However, heavier leaf coverage may prevent healthy turf growth and create conditions that contribute to damage during winter.
To better understand how much leaf cover a lawn can tolerate, researchers at the University of Wisconsin–Madison's O.J. Noer Turfgrass Research and Education Facility conducted a three-year study.
The research examined different leaf-mulching methods and depths under conditions designed to represent a typical residential lawn.
Researchers compared two-inch and four-inch layers of leaves, using both shredded and whole leaves. They also included plots that remained free of leaves throughout winter.
Each spring, the team assessed winter damage, grass quality, and turf color after removing the leaf cover. Conducting the study over three consecutive years helped account for differences in winter temperatures and snowfall.
Although the results have not undergone final analysis, preliminary findings indicate that a two-inch layer of shredded leaves can be acceptable for lawns during winter. In contrast, leaving a four-inch layer of accumulated leaves is much more likely to cause damage.
Homeowners can reduce these risks by shredding leaves instead of allowing whole leaves to build up on the grass. A lawn mower or suitable leaf-blower attachment can help break leaves into smaller pieces that decompose more easily.
The key recommendation is to keep leaf cover to a maximum depth of two inches and mulch the leaves whenever possible. Managing autumn leaves properly can help protect turf through winter and support healthier lawn growth in spring.
Photo Credit: university-of-wisconsin-madison
Categories: Wisconsin, General