Use these tips to determine the best height to cut your grass so your lawn is as healthy as possible.
Knowing the optimal height for cutting grass can help you grow a healthier lawn. The correct height settings for your lawn mower depend on several different factors, including the type of grass and the time of year. While it’s common to cut cool season grass to a consistent height of 3½ inches throughout the year, for example, your lawn will grow well with less water and fertiliser if you adjust your mowing height to suit the conditions. Start by getting to know your grass; each type of lawn has an optimal cutting height. Then consider seasonal factors such as heat and drought when adjusting your lawn mower blades. Here’s everything you need to know to determine the best height to cut your grass.
Know your weed
The type of grass that makes up your lawn helps determine the optimal height settings for your mower. Lawn grass is divided into two groups – cool season grasses and warm season grasses. If you live in a region that doesn’t get snow in the winter, your lawn is a warm season grass, such as Bermuda grass . Augustingrass, or zoysiagrass . If winter brings snow to your landscape, you probably grow cool-season grasses such as Kentucky bluegrass, tall fescue, or perennial ryegrass.
Homeowners in temperate coastal climates and the lower Midwest may grow cool-season or warm-season grasses. Here’s how to identify cool-season or warm-season grasses in temperate climates:
- If your lawn has a soft texture and stays green until late autumn, it’s probably a cool season grass.
- If your lawn has a coarse texture and turns brown quickly in cool weather, it’s probably a warm-season grass.
Lawnmower height settings for cool season grasses
Cool season grasses are typically mowed at a height of 2½ to 3½ inches. However, the optimum height for mowing cool season lawn grasses varies from season to season. These types of lawn grasses grow most vigorously when daytime highs reach the 70s and below – usually in spring and autumn. Expect them to turn green quickly in the spring when the days lengthen and temperatures rise. In spring, you will likely need to mow every five to seven days .
The recommended mowing height varies depending on the cool-season plant species. Set your mower blades to a higher cutting range to get a lawn with good heat and drought tolerance.
- Kentucky bluegrass: 2½ to 3½ inches
- Perennial ryegrass: 2½ to 3½ inches.
- Reed fescue: 3 to 4 inches
In summer, increase the height of the mower.
Summer brings a period of slow growth or dormancy for many cool season grasses as they conserve resources. It is not unusual for unirrigated cool-season grasses to turn brown in the summer; the roots are still alive and the grass will turn green again when moisture returns and temperatures drop. In summer, increase the mowing height by ½ to 1 inch. If you mowed grass at 3 inches in the spring, raise the blades to 3½ inches or 4 inches. The extra height helps shade the soil and encourages the grass to develop longer roots that can better extract water in drought.
Get your cool grass ready for winter
When the cool season grass starts growing vigorously again in early autumn, reduce the cutting height to 3-3 ½ inches to keep the grass looking uniform. Plan to mow every week until day length decreases and cooler temperatures arrive in late October. Cool season grass stays green for several weeks when high temperatures reach 50 degrees, but growth is minimal. Send your lawn to winter at a height of 3 to 3½ inches. Excessively long grass encourages vole and rodent activity in the winter, but grass that is too short can be affected by cold weather.
When mowing, never cut more than one-third of the grass height. For example, if the lawn is 3 inches tall, set the mower to cut at a height of 2 inches. Removing more than one-third of the leaf plate can shock the grass plant, resulting in thin turf and a shallow root system. If the lawn is overgrown, reduce the height by removing only one-third of the length at a time. It may take several mowings to bring the grass back to its former height.
Lawnmower height settings for heat-loving grasses
Mow warm season grasses at a much lower height than cool season grasses. The best height for mowing this type of grass is 1 to 2 inches. When mowed above the recommended temperature, warm season grasses are prone to developing a destructive layer of thatch . Thatch is an accumulation of dead stems and leaves on the soil surface. This prevents moisture from reaching the roots and slows growth, resulting in a lawn that is weak and thin .
During the summer, when the grass is actively growing, be diligent in maintaining the recommended mowing height for warm season lawns. You may have to mow twice a week to keep the grass at the ideal height. Here are the best heights for warm season grass cutting by species:
- Bermuda grass: 1 to 1½ inches.
- St Augustinegrass: 1 to 2 inches.
- Zoysiagrass: ½ to 1 inch.
Increase the cutting height in winter
In autumn, heat-loving grasses go dormant. As temperatures moderate and the days become shorter, adjust the mower height to the maximum of the recommended cutting range. Taller grass will encourage a deeper root system, which will help the grass survive the winter well. In the winter, warm season grass grows minimally or not at all in some areas. There is no need to mow warm-season grass when it is dormant except to control weed growth.
