When to Stop Mowing in Fall, and How Short to Cut the Last Mow

There are two common mistakes at the end of the mowing season. One is putting the mower away too early, while the grass is still growing, which leaves long grass under the snow. The other is “scalping” the lawn on the last mow so it looks tidy all winter. University turf specialists warn against both.

This guide covers when grass actually stops growing, how short the final cut should be for northern and southern lawns, and what to do with the mower afterward. MowReview quotes no prices and hasn’t tested the products mentioned. How we research explains why.

When grass stops growing

Purdue’s former turfgrass extension specialist, Zac Reicher, put it simply: “keep mowing as long as the grass continues to grow, which is normally into late October or early November.” You’ll mow less often as the weather cools, but you shouldn’t stop while the grass is still getting longer.

The signs that the season is over:

• The lawn looks the same a week after mowing.
• Hard frosts are regular, not occasional.
• On a southern lawn, the grass has turned tan or brown.

Fall growth matters more than it looks. Purdue says photosynthesis stays high in cool fall weather, so the grass is busy storing energy for winter and the spring green-up. Every cut that removes too much leaf takes some of that store away.

How short to cut the last mow

Northern lawns: a little shorter, never scalped

University of Minnesota Extension advises mowing “a little shorter going into the winter, but not lower than two inches.” A slightly shorter lawn reduces the risk of snow mold, makes it easier to collect leaves, and gives voles and mice less cover to tunnel under the snow.

Going too short has the opposite effect. Purdue warns against “the urge to set the mower down and scalp your lawn for the final mowing,” because it cuts off the leaf the grass needs to keep storing energy. And leaving the lawn long is a problem too: Purdue says unmowed grass encourages snow mold, a damaging turf disease.

In practice, if you normally mow tall fescue at 3.5 inches, drop to around 2.5 to 3 inches for the last cut or two. If you already mow at 2.5 inches, leave it there. See tall fescue and Kentucky bluegrass for normal heights.

Southern lawns: mow until dormant, then stop

Warm-season grasses work differently. Clemson’s Home and Garden Information Center suggests raising your mowing height by half an inch in mid-September if you aren’t overseeding, which helps shade out winter weeds and may encourage deeper roots. Keep mowing at that height until the grass turns brown. Once bermuda, zoysia, centipede or St. Augustine is dormant, it isn’t growing, so there’s nothing left to cut.

If you’re overseeding bermuda with ryegrass for winter color, the rules change: see mowing ryegrass over bermuda.

After the last mow

1. Deal with the leaves. Minnesota Extension says leaves left on the lawn block sunlight and trap moisture. Mulch light layers in with the mower, and bag or rake heavy ones. Mulching leaves with a mower explains how much is too much.
2. Run a gas mower dry, or stabilize the fuel. Purdue Extension says fresh fuel in spring is best, so run the tank out in fall if possible.
3. Use the winter for maintenance. Purdue suggests changing the oil and sharpening the blades over winter. Ohio State’s turf team recommends sharpening after every 25 hours of use, about twice a season.
4. Store batteries indoors. For cordless mowers, see how to store a cordless mower battery for winter.
5. Robot mower? See robot mower winter storage and the robot mower fall checklist.

The picks

Questions

When should I stop mowing my lawn in the fall?

When the grass stops growing, not on a set date. Purdue’s turf team says to keep mowing as long as the grass grows, which in Indiana is normally into late October or early November. Northern lawns stop earlier and southern lawns later.

How short should the last mow of the season be?

A little shorter than usual, but not scalped. University of Minnesota Extension says to mow a little shorter going into winter but not lower than 2 inches. Purdue warns against the urge to set the mower down and scalp the lawn for the final mowing.

Why shouldn’t I scalp my lawn before winter?

Grass is still making and storing food in fall. Purdue says photosynthesis stays high in cool fall weather, and cutting off leaf tissue reduces the energy the grass stores for winter and spring.

Does long grass over winter cause snow mold?

It can make it worse. Purdue says unmowed grass encourages snow mold, and University of Minnesota Extension says a slightly shorter final cut reduces snow mold risk and discourages voles and mice.

Should I keep mowing warm-season grass in the fall?

Yes, until it goes dormant. Clemson’s Home and Garden Information Center suggests raising the mowing height by half an inch in mid-September if you aren’t overseeding, to shade out winter weeds. Once bermuda, zoysia, centipede or St. Augustine turns brown and stops growing, there’s nothing left to cut.

What should I do with my mower after the last mow?

Purdue Extension suggests running a gas mower out of fuel in fall, then using winter to change the oil and sharpen the blades. If you can’t run it dry, treat the fuel with a stabilizer.

The short version

Keep mowing until the grass stops growing. On a northern lawn, make the last cut a little shorter than usual but not under 2 inches, and never scalp it. On a southern lawn, mow at your normal height until the grass goes dormant, then put the mower away. Run gas mowers dry, take batteries indoors, and sharpen the blades before spring.