Mowing grass accomplishes more than just keeping your lawn neat: it also keeps it healthy. You won't have to cut your grass as often during the dormant season as you do during the active growing season, but this timing varies by the type of grass in your lawn. Keeping your grass at an optimal height and ensuring you don't remove too much at once are the keys to maintaining a healthy, green lawn.
When to Mow
Grass needs mowing most during the growing season. For warm-season grasses, this is the summer; cool-season grasses grow in the spring and fall instead. Leave the grass clippings on the lawn -- as long as they're not wet and heavy -- to fertilize your lawn. These clippings can contain as much as 3 to 4 percent nitrogen and 2.5 to 3.5 percent potassium.
Frequency of Mowing
The rate of grass growth and desired height of your lawn determine how often you need to mow. Typically, mowing once a week during the growing season should suffice to keep your lawn healthy. The rest of the time, you can reduce the frequency of cutting to every other week, as necessary.
One Third Rule
It can be tempting to hack away at an overgrown lawn, removing most of the length of grass blades in one session, but this can stress the grass. Cutting too much grass at once steals the grass's food-producing parts, which starves the lawn and turns it brown. When you mow your lawn, remove only one third of the grass blades' height at a time. If you need to cut more than this, mow your lawn on a regular basis until it is at the height you desire -- but still, never cut more than one third at a time.
Lawn Height
Before you mow, ensure your grass is tall enough to justify it. Cutting grass too short can lead to weak root systems that are unable to easily absorb water and fertilizer. The result is unhealthy grass, unless you flood the soil with extra water and fertilizer. The ideal height for healthy grass is about 3 to 3 1/2 inches -- tall enough to develop deep, strong roots.
References
University of California Agriculture and Natural Resources: How Much, When, and How Often to Mow
Oregon State University Extension Service: It Is Best to Cut Grass Often and Leave Clippings on Lawn
Cornell University: Quick Tips for a Healthy and More Ecological Lawn
