Setting the Right Mowing Height

Man using measuring tape and scissors in grass to set the right mowing height

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What Mowing Height Should a Lawn Mower Be Set At?

Setting the proper height of cut varies depending on turf species, climate conditions and time of year.

Turf Species and Climate Condition

There are two types of turf species. Determine the turf species you have and then follow optimal cutting height guidelines by time of year below.

Cool season grasses (north of St. Louis). These are grasses like Blue, Rye, and Fescue grasses. Cool season grasses thrive and are most vigorous in the spring and fall but these grasses suffer the most in the summer due to the heat.

Warm season grasses (south of St. Louis). These are grasses like Bermuda, Zoysia, and Bahiagrass. Warm season grasses are the most sensitive coming out of dormancy in the spring and going into dormancy in the fall. These grasses thrive and are most vigorous in the heat of the summer.

Time of Year

Cool Season Grasses:
  • Summer – The optimal cutting height for cool season grasses is anywhere from 2” to 3”. It’s generally a good idea to raise your mower’s deck slightly, to about 3”, in the middle of the summer to give the turf a break too.
  • Spring/Fall – The optimal cutting height is  2” to 2 ½” in the spring and fall when the turf is the most vigorous.
Warm Season Grasses:
  • Summer – There is less of a need to raise the deck height to 3″ in summer as these grasses don’t suffer as much from the heat.
  • Spring/Fall – Overall, warm season grasses respond a little better to a shorter height of cut, so we recommend setting the mower height anywhere from 1” to 2” in length.

How Do You Measure Lawnmower Height?

A good rule of thumb is to never remove more than 1/3 of the grass blades in a single mowing and don’t take off more than 1 inch at a time. That means you might be cutting twice a week when the grass is in its peak growing season, but the payoff will be a healthier, better-looking lawn.

What Height Should New Grass be Cut?

For your first mowing, remove just enough (1/2- to 3/4-inch) to give your lawn an even appearance.  Next time, cut to the maximum height recommended for your type of grass, but do not remove more than 1/3 of the blade in any single mowing.

How Tall Should You Let New Grass Grow Before Cutting?

Sod: Do not mow a sodded lawn for at least 10 days after installation and until the grass has begun to grow vigorously.

Seed/Plugs/Sprigs: Begin mowing after the grass has grown to a height of 3 or 4 inches —before it falls over in a slight breeze.

Is it Better to Cut Grass Short or Long?

It’s better to cut grass long. When left a little tall, the grass shades the soil, so it retains moisture better and promotes cooler soil and healthier grass. Keeping grass longer also allows its greater surface area to carry out photosynthesis, which in turn results in healthier plants.

In addition, taller grass grows slower than shorter grass.  You can use this fact to eliminate up to 20 percent of the mowing you do annually—an average savings of about eight hours a year, not to mention the savings of gasoline and wear on equipment.

Lastly, by keeping your grass at the upper end of its recommended mowing height, you can prevent most weeds from germinating—and thereby eliminate the need for herbicides.

What Happens When You Cut Grass Too Short?

Cutting grass too short forces the grass to tap into its food reserves, which stresses the roots and will eventually thin out your turf. The shorter you mow, the shallower the root system. The taller the height of cut, the deeper the root system. The root system supports the top of the plant and deep roots are important for harvesting moisture and nutrients from the soil.