Mowing Height Matters

Nothing signals springtime quite like the smell of fresh cut grass wafting through the neighborhood. With warmer weather on the way, your annual lawn duties begin. Of those tasks, mowing at the right height can have a big impact on the overall health of your turf and future weed problems.

Grass 2015 May_JunThe first mowing makes the lawn look spring-like and very attractive. Subsequent regular mowing hardens the grass for drought and heat stresses later on. So when the first clump of grass grows above the mowing height, mow — even if a lot of the yard doesn’t need to be mowed yet.

If your lawn is not greening up as quickly as your neighbors it’s important to note that not all grasses start growing at the same time. Grass that wasn’t fertilized in the fall or early spring has a delayed growth. Also, grass on northern slopes, or in heavy clay soil, will start growing several days later than others.

Following recommendations for mowing height and frequency will make your lawn-care duties easier and result in a more attractive yard. If your mower has a fixed, all-year height, set it at two and one-half inches for cool season grasses. However, if you can easily vary the height, set it at 1.5 to two inches for the first several times you mow this spring. The shorter mowing height will help remove a lot of the winter-burned, brown leaves. Exposing more dark green growth will transform your lawn into the most uniform, attractive one in the neighborhood. Move the height up to 2.5 inches after you mow the grass several times.

To protect your grass from summer heat and drought injury, when summer arrives raise the mower height to three or 3.5 inches. Mowing grass a greater height can also impact weed growth. As the leaf blades are left longer they overlap more and shade the soil surface reducing the amount of sunlight penetrating to the ground and increasing competition for emerging weed seeds. However, remember that extra high grass, especially tall fescue, tends to fall over and mat down during hot summer weather causing increased summer disease problems.

Once you get the mowing under way, how often should the lawn be mowed? Generally speaking, mow often enough to remove no more than one-third to one-half of the grass height. If your mower is set for two inches, mow again when grass height reaches approximately three inches. Be sure not to scalp the lawn by mowing off most of the green leaves.

For tall fescue lawns, a rule of thumb is to mow at five-day intervals during the spring, and at seven-day intervals the rest of the year. If you have a Kentucky bluegrass lawn, a seven-day interval usually is sufficient at a mowing height of 2.5 inches. That interval can probably be expanded during hot, dry weather.

A sharp mower blade makes mowing easier and results in a better-looking and healthier turf. Dull blades will tear at the tender new turf leaving jagged and torn edges on the leaf blades. These edges tend to dry out leaving a brown look to the lawn and exposing leaf surfaces to disease.

For more information contact your local extension service. Find your local office here:

Submitted by Kelly Jackson, Agent for Horticulture, Christian Co. Cooperative Extension Service