Should Your Lawn Mower's Deck Be Set Higher Or Lower During Fall?

After a long summer of hard work to keep your lawn in top shape, you might be eager to put your mower away for the year as soon as the autumn leaves start to drop. However, it's important to keep mowing your grass through the fall until cold temperatures finally stop its growth. As the growing season winds down, adjustments need to be made to the height of your mower deck. So, should you set it higher or lower in fall?  It all depends on your grass type and summer mowing height. Cool-season grasses generally do best at 2½ to 3 inches, while warm-season grasses typically need 2 inches, depending on the species. Grass needs to be tall enough to have a healthy root system, but not so long that it's vulnerable to fungal diseases and pests.

The goal of fall mowing is to prepare your lawn for winter, not simply to cut it as short as possible. Very short grass tends to have a weak root system and isn't able to photosynthesize effectively, and considering how stressful winter can be for lawns, you want your turf to go into the cold season as strong as possible. However, a lawn that's too long in winter can easily become an ideal habitat for voles and leave you with significant rodent damage in spring. Diseases like pink snow mold are also common in taller grass because the extra height encourages the blades to bend over and hold onto water. This moist environment is the perfect habitat for fungi that can damage your turfgrass.

If you need to adjust your deck to ensure your grass is cut to the recommended height, it should be a fairly simple process. On some mowers, you may have to reposition levers on the wheels to set the lawn mower's height, while on other machines it could be as easy as turning a dial. Be sure to consult your mower's instruction manual for help, if necessary. If your mower doesn't clearly show the height each deck setting will cut your grass to, don't hesitate to take out your tape measure and check the distance between the mower blade and the ground. A hard, flat surface like a stone patio is the best place to do this.

In most cases, there shouldn't be much, if any, difference between your summer and autumn mowing heights, but, for example, if you've let your grass grow to 4½ inches or more during summer and want to drop the height to 2½ inches in autumn, it's important not to do it all at once. This is because grass, like most plants, shouldn't have more than a third of its growth removed at a time. Mowing too much at once stresses the lawn and makes it more vulnerable to damage and disease. So instead of giving your turf one big chop to get it down to your preferred fall height, do it in stages. First, lower your mower's deck enough to cut the grass just a bit. Then, after a few days, you can drop the deck a little more and give your lawn another mow. It shouldn't take long to smoothly transition your grass to the lower height.