When Should You Start Mowing Your Lawn in the Spring?

As a teen, I was eager to start mowing lawns in spring — it meant extra spending cash. Some clients wanted the first cut of the season the moment they saw any new growth. Others let the days pass until they were sure spring had arrived. That usually wasn’t a problem, unless their dog had left highly fertilized spots of dark green grass, which grew much faster than the surrounding turf. I can still hear my poor mower going “whomp!” as it hit those thick patches.

Deciding when to cut the grass for the first time in spring isn’t as simple as saying, “just start mowing when the grass starts growing.” The weather will have a lot to do with it, and so will the vigor of the turf. Ahead, you’ll find expert tips on when to cut grass for the first time in spring from an extension specialist in turf maintenance.

When to Start Mowing Your Lawn in the Spring

Spring arrives earlier in some years than others, so you can’t always rely on the calendar to determine when to start mowing your lawn in the spring. The answer also depends on your region of the country and the type of grass you’re growing. For example, Kentucky bluegrass is a cool-season grass that grows rapidly in spring and may require attention early and often, while Zoysiagrass is a warm-season grass that doesn’t “wake up” until April or May in the South and even June in colder climates.

“Start mowing once the grass starts growing and has firmed up from the frost leaving the ground,” says Adam Thoms, Ph.D., turfgrass extension specialist for Iowa State University. The first mowing helps stimulate growth, so subsequent mowings might come more frequently.

“Typically, you would want to mow with an old mower blade the first time, as there will be rocks, sand and twigs from the winter that you will hit and those would damage a freshly sharpened mower blade,” Thoms says. Switch to a freshly sharpened blade after that.

What is the Ideal Height to Cut Grass?

While most grasses are kept at a height of 2 to 3 inches, there are exceptions. Experts recommend keeping grass a 1/2 inch longer in summer to help cool the crowns of the turfgrass plants and provide more leaf area for photosynthesis.

On the other hand, the last cut in fall might be shorter than normal to discourage vole activity. “Remove no more than one-third of the leaf tissue,” says Thoms. “Removing more than one-third of the tissue at a time will cause stress on the plant.”

Best Weather for Mowing Grass

Let the grass dry out from rain or morning dew. Wet grass clumps up and looks unsightly. The clippings can also clog the mower, causing it to stall or overheat. Wet grass is also slippery, posing a safety hazard on slopes. “You don’t want to mow if you have a riding mower and it is wet, as this can cause damage and in some cases increase the soil compaction,” Thoms says.

What Temperature Is Too Cold to Mow Grass?

Spring weather can be fickle. It’s hard to predict when cold weather is truly behind us. Temperatures should be consistently above 40 degrees F. before you attempt your first mow of the spring. “Never mow grass if there is frost on it, as this will damage the plant,” Thoms says. “Let the frost burn off.”

What if it Gets Cold or Snows Again?

“That is not a big issue with cool-season grasses,” Thoms says. “They might try to go dormant again, but once the weather becomes favorable, they will green up again.”

As for warm-season grasses, the new tissues of spring growth are tender and more prone to environmental stresses early in the season, and serious damage can happen if low temperatures (20s or less) occur during green-up.

When to Fertilize and Water Your Lawn

A soil test will indicate what nutrients are needed. Fertilizing is generally done once or twice a year: in spring and late summer/early fall. “Fertilizing in the spring is often associated with applying a pre-emergence herbicide for crabgrass,” Thoms says. “If you are doing these tasks together, you will want to apply them before you have three consecutive days of soil temps at 55 degrees or more. Most state extension services will have soil temperature maps for every county available on the internet.”

Generally, grass should be watered early in the morning so blades can dry off before nightfall and avoid disease. “Turfgrass needs 1 inch of water per week for active growth,” Thoms says. “If you are getting regular rains, you will not need to water in the spring.”

FAQ

What Happens If I Mow Too Early?

Nothing much happens if you water to early unless there is frost or the soil is soggy. Grass can be damaged if mowed when frost is present, and the ground can become compacted and leave ruts if you run a lawn tractor over a lawn when the soil is soggy.

Should I Rake the Grass Before the First Mow?

Raking is a good idea before the first mow of the season to remove sticks, pine cones and any other debris you don’t want to run over with the mower.

Should I Bag the First Mow of the Year?

“No, mulching is the best method,” Thoms says. “I would only rake the yard to spread out clippings if they piled up in a spot and were smothering the surface of the lawn. Leaves should mulch nicely.”

Should I De-Thatch My Lawn?

De-thatching is useful if there is a buildup of dead grass (thatch) due to poor aeration, improper watering or overuse of fungicides. “If you have more than ¾-inch-thick layer of thatch on a cool-season lawn, you should consider dethatching,” Thoms says. “Often people want to do this yearly, but it is not necessary. You are better off aerating the yard each year to relieve compaction. Aerating will improve turfgrass rooting, allow more water to enter the soil, and reduce soil bulk density, which will all improve growing conditions for the yard.”

About the Expert

Adam Thoms is an associate professor of commercial turfgrass in the Department of Horticulture and the Turfgrass Extension Specialist for Iowa State University. He teaches, conducts trials on new cultivars and products, and researches managing turfgrass more sustainably. Thoms has M.S. and Ph.D. degrees from the University of Tennessee.