The Complete Guide to Lawn Mowing in Pennsylvania

Mowing a lawn seems straightforward until you start paying attention to the details. Cut it too short and you’re inviting weeds. Cut it too infrequently and you stress the grass. Mow at the wrong time of year and you can actually damage a lawn that was doing just fine.

Pennsylvania lawns have their own rhythm. We’re in the transition zone, which means most of us are growing cool-season grasses like Kentucky bluegrass, perennial ryegrass, and fescues. These grasses behave differently than what you’d find in the South, and the advice you read online doesn’t always account for that. So here’s what actually matters if you’re mowing a lawn in this part of the country.

When to Start Mowing in Spring

The urge to get out there as soon as the snow melts is understandable, but patience pays off. According to Penn State Extension, you should wait until the grass is actively growing and the soil has firmed up enough that you won’t leave ruts or compact the ground by walking on it.

In most of Pennsylvania, that means late April or early May for the first mow, though a warm March can push that earlier. The real signal isn’t the calendar—it’s the grass itself. When it reaches about three and a half inches, it’s time to cut. Mowing before the lawn is ready, especially when the soil is still soft from snowmelt, does more harm than good.

For that first cut of the season, you can go a little shorter than usual to remove the dead tips that accumulated over winter. Penn State suggests cutting to around two to two and a half inches initially, then raising the deck back up as the season progresses.

How High to Cut

Mowing height matters more than most people realize. The general rule for cool-season grasses in Pennsylvania is to keep them between two and a half and three and a half inches tall. During the hottest parts of summer, lean toward the higher end. Taller grass shades the soil, keeps roots cooler, retains moisture better, and crowds out weeds.

The Pennsylvania Department of Conservation and Natural Resources puts it simply: longer grass produces more shade for the soil, which encourages deeper roots and reduces heat damage. Scalping your lawn to make it look like a golf course fairway might seem tidy, but it weakens the grass and opens the door for crabgrass and other problems.

There’s an old rule of thumb called the one-third rule: never remove more than one-third of the grass blade in a single mowing. If your lawn is six inches tall and you cut it down to two inches, you’ve stressed the plant significantly. It’s better to make two passes over a few days than to shock the grass with one aggressive cut.

How Often to Mow

This depends entirely on how fast your grass is growing, which changes throughout the year.

In spring, cool-season grasses grow aggressively. You might need to mow every four to five days during peak growth in May. This is when most homeowners fall behind, and then they’re stuck either scalping the lawn or leaving clumps everywhere.

Summer slows things down. When temperatures climb and rain becomes less frequent, growth slows too. You might stretch to every seven to ten days, or even longer during a drought. Penn State Extension notes that during dry periods, your lawn may not require mowing at all until rain returns and active growth resumes.

Fall picks back up as temperatures cool and moisture returns. September and October often see another growth spurt, so expect to mow more frequently again before things wind down for winter.

The key is to watch the lawn, not the calendar. Mow when the grass needs it based on its height, not because Saturday is your mowing day.

When to Stop Mowing in Fall

Knowing when to put the mower away matters just as much as knowing when to start. According to Penn State Extension, you should continue mowing as long as the grass is growing. In Pennsylvania, that typically means late October or even into November depending on the weather.

Your final mow of the season should leave the grass a bit shorter than usual—around two to two and a half inches. This helps prevent snow mold, a fungal disease that thrives when long grass gets matted down under snow. The Pennsylvania DCNR recommends this shorter final cut specifically to reduce disease risk over winter.

Once daytime temperatures consistently drop below forty degrees, growth stops and so should your mowing. Cutting dormant grass doesn’t help anything and can actually injure the crowns of the plants.

Time of Day Matters

Mid-morning is the best time to mow, roughly between eight and ten in the morning. By then, the dew has dried but the heat of the day hasn’t set in yet. Mowing wet grass leads to uneven cuts, clumping, and can spread disease. Mowing in the midday heat stresses both you and the lawn.

Late afternoon, around four to six in the evening, is the second-best window. The temperature has cooled off, the grass is dry, and there’s still enough daylight for the lawn to begin recovering before nightfall.

Avoid mowing in the evening as darkness approaches. Grass needs time to heal from cutting, and moisture that settles overnight on freshly cut blades can encourage fungal problems.

Keep Your Blades Sharp

This is one of the most overlooked aspects of lawn care. A dull mower blade doesn’t cut grass—it tears it. You can actually see the difference: a clean cut leaves a neat edge on each blade of grass, while a dull cut leaves ragged, brown-tipped ends that make the whole lawn look unhealthy.

Sharp blades also reduce stress on the grass plant, which means faster recovery and better resistance to disease. Most professionals sharpen or replace blades every ten to twenty hours of use. For a typical homeowner, that might mean sharpening once or twice per season.

If your lawn looks grayish or brown a day or two after mowing, check your blade. That discoloration is often torn grass tips dying back, not a watering or fertilization issue.

Mowing Patterns

Mowing in the same direction every time compacts the soil along your wheel tracks and can cause the grass to lean permanently in one direction. Changing your pattern—alternating between north-south and east-west, or mixing in diagonal passes—keeps the lawn healthier and helps the grass grow more upright.

This isn’t just cosmetic. Compacted soil restricts water and nutrient movement to the roots. Alternating patterns is a simple habit that prevents long-term problems.

Clippings: Leave Them or Bag Them

In most cases, leave them. Grass clippings break down quickly and return nitrogen and other nutrients to the soil. The University of Minnesota Extension found that recycling clippings can provide up to twenty-five percent of a lawn’s annual fertilizer needs.

The only times to bag are when the grass is excessively long and clippings would smother the lawn, when it’s wet and clippings clump together, or when you’re dealing with a fungal disease and want to prevent spreading it.

There’s a persistent myth that clippings cause thatch, but that’s been disproven. Thatch comes from stems and roots, not leaf blades. As long as you’re mowing regularly and not leaving behind heavy clumps, the clippings will disappear into the lawn within a week or two.

Putting It All Together

Good mowing comes down to a few habits: cut at the right height, mow frequently enough to follow the one-third rule, keep your blades sharp, and pay attention to what the grass is telling you. None of this is complicated, but it does require consistency.

A well-mowed lawn isn’t just about appearance. It’s healthier, more drought-resistant, and better at fighting off weeds and disease. And in Pennsylvania’s climate, where we get hot summers, cold winters, and everything in between, giving your lawn the best chance means working with the seasons instead of against them.

Sources

Penn State Extension. “Lawn Management Through the Seasons.” https://extension.psu.edu/lawn-management-through-the-seasons

Pennsylvania Department of Conservation and Natural Resources. “Mowing Practices.” https://elibrary.dcnr.pa.gov/

University of Minnesota Extension. “What to Do with Lawn Clippings.” https://extension.umn.edu/lawn-care/what-do-lawn-clippings