Mowing is More Than Just Cutting the Grass
It’s that time of year again—when the hum of lawn mowers and the smell of freshly cut grass fill the air. With recent rainfall and warming temperatures, cool-season lawns are beginning to grow. Many homeowners have already applied fertilizer and weed control, but even the best lawn care products won’t deliver a picture-perfect yard without proper mowing practices.
The single most important factor in mowing is maintaining the correct height. This varies depending on the type of grass. Cool-season grasses, such as tall fescue, grow more upright and should generally be kept at a height of 2½ to 3 inches. Cutting these grasses too short—often called “scalping”—can severely reduce root growth. During hot weather, this added stress increases the lawn’s water needs and can weaken the turf, making it more vulnerable to weeds.
In contrast, warm-season grasses like bermudagrass and zoysiagrass grow closer to the ground and should be mowed shorter, typically between 1 and 2 inches. Mowing these grasses too high can lead to excessive thatch buildup, which can negatively impact lawn health. Clearly, mowing height plays a key role in overall turf quality.
So how do you know when it’s time to mow? Many homeowners mow based on their schedule—or when the grass becomes noticeably tall. However, mowing frequency is critical to maintaining a healthy lawn. A helpful guideline is the “one-third rule”: never remove more than one-third of the grass blade in a single mowing. This means your mowing schedule should be based on how fast the grass is growing rather than a fixed calendar. While this can be challenging with busy schedules, it leads to stronger, healthier turf.
For newly planted lawns, early mowing is beneficial. Cool-season grasses should be trimmed to about 2 inches once they reach 3 inches tall. Warm-season grasses should be cut to 1 inch when they grow to about 2 inches. As long as mower blades are sharp, mowing will not harm new grass—in fact, it encourages it to spread and fill in more quickly.
Before mowing, always check your blade sharpness. Sharp blades are essential for a clean cut. Dull blades tear the grass, leaving ragged edges that give the lawn a whitish appearance and increase the risk of disease. Sharp blades not only improve lawn appearance but also make mowing more efficient and reduce fuel use. Additionally, mowing at a steady, safe speed—around 3 to 5 mph—helps ensure an even cut and minimizes stress on the turf.
Another common concern is what to do with grass clippings. Many homeowners remove them, believing they contribute to thatch buildup. In reality, this is a myth. Grass clippings are made up of 85 to 90 percent water and decompose quickly, returning valuable nutrients to the soil. If you follow the one-third rule, clippings will be short enough to settle into the lawn without causing problems. Mulching mowers can further break down clippings, making them even more beneficial. In fact, regularly leaving clippings on the lawn can reduce the need for nitrogen fertilizer. If clippings are consistently removed, you may need to increase nitrogen applications by about 25 percent to maintain the same nutrient levels.
Proper mowing is more than a routine chore—it’s a cornerstone of effective lawn care. By mowing at the right height, frequency, and technique, you can cultivate a lawn that is not only attractive but also healthy and resilient throughout the growing season.
Krista Harding is a K-State Research and Extension horticulture agent serving the Southwind District. She can be reached at kharding@ksu.edu or 620-244-3826.