The fall season is a transition period where proper mowing techniques prepare the lawn for winter dormancy. Fall mowing aims to manage the growth rate, optimize photosynthesis for root energy storage, and prevent conditions that foster winter diseases. This strategic approach ensures the turf’s health and resilience, helping it withstand cold temperatures, snow cover, and frost until spring.
Determining Mowing Frequency
Mowing frequency should be determined by the grass’s growth rate, not a fixed calendar schedule. As temperatures cool and daylight hours shorten, growth naturally slows down. Early in the season, cool-season grasses (like Kentucky Bluegrass or Fescue) may surge due to favorable soil temperatures, requiring a weekly cut. As the season progresses and soil temperatures drop below 50°F, growth decelerates, and mowing may only be necessary every 10 to 14 days.
The “one-third rule” dictates when to mow: never remove more than one-third of the grass blade’s height in a single session. For a lawn maintained at a three-inch height, this means mowing before the blades exceed four and a half inches. Adhering to this rule minimizes shock and ensures the plant retains sufficient leaf surface for photosynthesis and storing energy for the winter.
Adjusting Cutting Height
Adjusting cutting height involves progressively lowering the mower deck over several weeks. Initially, maintain the summer height to maximize leaf surface area, allowing the grass to build carbohydrate reserves. Taller blades early in the season also shade the soil, conserving moisture and encouraging deeper root development.
Once the most active growth period passes (typically mid-fall), gradually reduce the height with each subsequent mow. The final target height, achieved over the last few cuts, should be 2 to 2.5 inches for cool-season grasses. This shorter height prepares the turf for winter, preventing excessively long grass from matting down under snow and fostering fungal diseases like snow mold.
Managing Clippings and Leaf Debris
The mower plays a dual role in the fall by both cutting the grass and processing organic debris like fallen leaves. Grass clippings should be left on the lawn, as they decompose quickly and return valuable nitrogen and other nutrients back to the soil. This natural nutrient recycling can significantly reduce the need for synthetic fertilizers.
When dealing with fallen leaves, the mower can be used to shred them into fine particles through mulch-mowing. Mulched leaves should be small enough, ideally dime-sized, to filter down between the grass blades, where they act as a natural soil amendment. Leaving a thick, unshredded layer of leaves is detrimental because it blocks sunlight and air circulation, traps excessive moisture, and can smother the grass, making it susceptible to disease and pests. If the leaf cover is too heavy to mulch in a single pass while still allowing 80 to 90% of the grass to be visible, the excess material should be removed.
Timing the Final Cut of the Season
The last mow of the year should be determined by a biological cue: the complete cessation of grass growth. This usually occurs after the first few hard frosts have killed off the top growth and the soil temperature has dropped consistently below 50°F. Continuing to mow until this point ensures the grass does not go into winter too tall, which is a primary factor in the severity of winter damage.
The final cut should be executed at the lowest recommended height for winter preparation, typically 2 to 2.5 inches for most turf types. This short length minimizes the risk of the grass blades folding over and matting under snow, which prevents the moisture buildup that encourages snow mold. While the exact timing will vary geographically—later in southern climates where warm-season grasses may continue slow growth, and earlier in northern regions—the principle remains the same: the mower is put away only when the grass has definitively stopped growing.