Taller grass shades out weed seeds and keeps soil cooler. Taller grass means longer roots and greater ability to withstand drought and reach nutrients.
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.
Taller grass also shades the ground, slowing weed growth and water loss from the soil. The ideal length of your lawn depends on your climate, but most experts agree you should keep your grass between 2 1/2 inches to three inches long, with the last cut of the season remaining the same.
Cut your lawn to possibly the shortest height you have all season. The ideal height is around 2 1/2 inches. Cut it too low and the grass might not be long enough to photosynthesize and provide nutrients to the roots. Too high and the frost might become matted after a snowfall.
Reasons to Avoid Cutting Grass Too Short
A larger surface area is needed for photosynthesis to occur. Limiting the amount of sunlight and air that your grass is exposed to can inhibit successful development and weaken the plant's roots. This can in turn leave your lawn vulnerable to invading weeds, diseases and pests.
A smaller surface area permits less exposure to air and sunlight, which means less photosynthesis and less energy. A weakened blade leads to weakened roots, which are more vulnerable to insects and diseases. If damaged grass begins to die off, the resulting space will be hospitable to weeds.
The simple answer to this question is NO. Allowing your grass to grow too long between cutting creates lawn care problems that no homeowner wants to deal with.
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.
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.
Generally, the cutoff point comes when temperatures drop below 50°F during the day. Usually, that's late October or early November, but some warm areas may push that date back to the beginning of December.
Cool-season grasses should typically be cut to about 3 to 4 inches high. Warm-season grasses should typically be cut to about 2 to 2 ½ inches high. The common cool-season grasses include fine and tall fescue grass, Kentucky bluegrass, and perennial ryegrass.
Typically, most warm-season grasses should be at least 1 inch high and most cool-season grasses should be at least 2.5 inches high. You may also be scalping if you regularly cut the grass at your mower's lowest setting.
A longer lawn means that the individual grass blades (the leaves) have more surface area for photosynthesis to occur. Increased photosynthesis results in more plant growth, a more extensive root system, and a healthier plant.
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.
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.
Cutting grass too short allows weed seeds easy access to sunlight, whereas longer grass blocks this light from getting to the weed sprouts. Mow your grass no more than a third of its length at a time; it's better to have longer grass than shorter grass.
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. In the fall, consider cutting to 2 inches high, as no new weeds come up at that time, to faciliate fall clean-up.
Mow your cool season grass to 3 or 3.5 inches in summer, or up to 4 inches for tall fescue and perennial ryegrass. Warm season grasses should round out at about 2 to 2.5 inches.
Perform the first grass cut of the year in spring, around mid-March. From there on, mow the lawn at least once every week. Try to keep your grass' height the same all throughout spring. For most lawns the ideal height would be 2.5-4cm (1-1.5in).
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.
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.
In a drought, taller grass retains moisture better and thus stays greener longer than shorter grass. You can get away with less frequent watering if you cut your bluegrass to 2 to 3 inches, tall fescue to 3 inches, perennial ryegrass to 2 inches.
Long Grass Problems
This causes it to droop onto surrounding grass, smothering it. When long grass droops, it also traps moisture in lower areas, which can cause fungus and disease to spread. At this length, grass also looks unseemly. It may grow unevenly or turn yellow or brown.
Taller grass reduces the need for watering.
These deep roots help your grass handle hot and dry summers because they have access to water stored deep within the soil. Tall grass blades also shade the soil, which reduces moisture evaporation while simultaneously cooling the crowns of the grass.