For the healthiest and most sustainable approach, Michigan State University Extension says 3.5 to 4 inches is most desirable. Lawns mowed at 3.5 or 4 inches out-compete weeds, tolerate grubs and look just as good as lawns mowed at 2.5 inches.
For a typical residential Midwest lawn, maintain a height of 3 inches or higher. Taller grass shades out weed seeds and keeps soil cooler.
In the summer, keep both cool-season and warm-season grasses slightly taller. Cut cool-season grasses to 3 or 3 ½ inches. Mow warm-season grasses to 2 or 2 ½ inches. In summer, grass can be kept a bit higher to prevent weeds, help shade the soil line, and maintain water in the soil.
Proper Mowing
Mow the lawn as high as possible—as high as you can comfortably tolerate. A longer lawn means more leaf blade, and this provides several benefits. More leaf blade means more photosynthesis, which results in stronger, more prolific root and shoots growth.
What Length Should Grass Be Cut for Optimal Results? Ideally, during warm weather, grass should be kept as high as possible. For most circumstances, the blades should be kept somewhere around 2 to 2.5 inches in length.
Mowing actually helps make your grass grow thicker because the tip of each blade contains hormones that suppress horizontal growth. When you cut the lawn, you remove these tips allowing the grass to spread and grow thicker near the roots.
For a good-looking, weed-free, well-hydrated lawn, allow your grass to reach 3.5- to 4.5- inches in height before each mow.
If the grass is too wet, you shouldn't mow and if it's too dry you shouldn't either. Remember, mowing is a stressful event for your lawn. If you mow when it's already under stress, such as during dry spell or drought, then it will become even more stressed. You don't like to be stressed and neither does your poor lawn.
How often should you mow? Normally, weekly mowing is the rule, but some lawns need cutting more often. Other lawns will grow more slowly and might need cutting only once every ten days or two weeks. Generally, don't cut off more than one third of the grass blade.
During a heat wave—a period of abnormally hot weather that lasts longer than 2 days—it's recommended that you do not mow your lawn.
Lawn clippings usually do not need to be bagged. Recycling lawn clippings can reduce your fertilizer needs and improve your soil. Recycling clippings to the lawn does not contribute to thatch. If you must remove clippings, they can be composted or used as mulch.
A dull blade and cut too short is a guaranteed way to burn out and kill the grass during extreme heat. Ideally, keep your grass 3+ inches tall for most of the season. In extreme heat, consider leaving your lawn 4 inches tall for maximum resistance.
For this reason, some people prefer to mow at 3 or 3.5 inches. For the healthiest and most sustainable approach, Michigan State University Extension says 3.5 to 4 inches is most desirable. Lawns mowed at 3.5 or 4 inches out-compete weeds, tolerate grubs and look just as good as lawns mowed at 2.5 inches.
A mowing height between 2.5 to 3 inches is best for most of the season, except during summer stresses when the lawn mowing height should be raised one-half inch to mow at 3 to 3.5 inches. Raising the mowing height provides more insulation from summer heat and reduces water loss from your soil.
You'll know you're cutting too short if brown and tan patches begin to appear on grass blades. What Height Should Be My Goal? Once the weather warms up, most types of grass should be kept between two and two and a half inches.
However, most professional gardeners would agree that between 8 AM and 10 AM is the best time of day to cut your grass. The reason for that is that lawns need time to heal before evening. Grass needs the benefit of the day to dry and heal before dusk settles.
As a general rule your first grass cut of the year should be in early Spring. Depending on weather and temperatures at the particular time, the last week in February or the first week in March is a great time to start.
Mid-morning (between 8 and 10 a.m.) tends to be the best time of day for mowing your lawn. It allows enough time for dew to dry, resulting in strong, perky blades of grades, while avoiding the hottest periods of the day.
Longer grass reduces the amount of weeds.
The extra shade given off by long blades of grass helps prevent light from reaching weeds and crabgrass. Without light, the unwanted weeds can't germinate, and you won't have to put up with them taking root in your beautiful lawn.
The best height to cut grass in the fall
Focus on striking the right balance in fall so your lawn's ready for winter. Shorten your cool season grass to about 2.5 inches before the first frost in winter.
60% of weeds in any lawn can be controlled with proper, weekly mowing. 60%!! You cannot rely on herbicide applications completely, weekly mowing HAS to be part of your plan to control weeds. So, let me reiterate…the presence of weeds in your lawn is NEVER a good reason to skip a mow.
Mowing every two weeks — instead of weekly — and not dousing grass with chemical herbicides and fertilizers, helps the environment and supports the health of bees, which are among the world's most important pollinators.
The short answer is yes, according to lawn care experts. Leaving grass clippings on the lawn can actually be healthy for the grass, as it helps build a strong and nutrient-rich soil. This practice is known as “grasscycling,” and it has become increasingly popular in recent years.