A lawnmower has a setting that most owners use: however it came from the factory. This works until the weather changes and then it really doesn’t. Cut too close in the heat of summer and the grass burns, or leave shaggy through a wet spring and it spoils and causes disease. The correct cutting height is not a number. It changes with the season.
But there is more to learn how to mow a lawn rather than selecting the correct cutting height and forgetting about it. It is also important to know when to change the cutting height. A lawn thrives in spring, then crawls as the heat of summer sets in. So a height that works for it in May doesn’t do your lawn any favors until August.
Change your mowing and you’ll be rewarded with a lush green lawn with gorgeous green color and fewer weeds. Here’s how to do it right.
Always follow the rule of thirds
Before prescribing any specific number for the season, one rule governs it all: never remove more than one-third of a blade of grass in a single cut.
Get any closer and it loses too much card at once. Roots stop while your grass recovers. The crown also sits uncovered, and some haircuts in the lawn look thin and stressed, darkening in patches over weeks.
This is also why height changes should occur gradually with a few haircuts, rather than a drastic drop. It helps you know your current height before adjusting anything. Place the mower on a flat, hard surface and measure from the ground to the edge of the blade.
Measurement is easier with a height measuring instrument from Amazonalthough a simple measuring cup does the job just fine. The eyeball can end up shorter and short is the direction that causes problems.
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Spring: Start low, then relax
Spring is the only time you can cut a touch closer. That first cut of the season it may come in a touch lower than usual to clean up the dead, tangled winter it left behind. This lets sunlight and wind down to the crown to wake up your grass faster. For cool season greens like fescue and bluegrass, that means starting about 2.5 inches (6 cm).
Once your lawn is seriously grown, raise the deck again. For most cool-season lawns, about 3 inches (7.5 cm) is the spring sweet spot. It is tall enough to shade the soil and crowd out weed plants, but short enough to keep the grass from falling over.
Warm season grass types it should be cut lower, about 1-2.5 inches (2.5-6.4 cm) tall. Bermuda, zoysia, southern grasses do well below this height. But the logic still applies. Lower the winter-killed plant to green, then allow the height to increase as it grows through the season.
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Summer: Let it grow tall
Summer is the time when cutting height is most important. Let the grass grow a little longer and shade its soil, cooling the roots and slowing how quickly the water above burns off.
In a brutal July, when the heat won’t let up and the rain is hit or miss, this shade is key to keeping your lawn green. Cool-season lawns would prefer a high cut here, up to about 3.5 to 4 inches (9-10 cm).
Longer blades also develop deeper roots, which reach the water further down when the surface dries out. Resist the urge to scrub your scalp to cut less often. This quickly fails in July, leaving you heat stressed grass and making your own the lawn turns brown.
Warm-season grasses withstand the heat better and can be kept closer to their usual height, although even they appreciate a slightly higher cut due to poor drought.
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Drop: Bring it back
When temperatures finally cool, cool-season grasses get their second wind and spring-like vigor again. The deck goes down with it to the same 2.5 to 3 inches (6-7.5 cm) from the spring.
Autumn is a time of recovery. The lawn rebuilds after the summer by knocking and sending growth down to the roots. A medium height gives it room without sitting so high that it’s exposed.
THE last cut of the year it’s what needs to be done right. Dropping it down a notch for that final cut, to 2 inches (5 cm) high, prevents the long blades from shearing under the snow and away snow mold during the winter.
Autumn is also the season of leaves and a ground cover blade from Amazon chop the fallen leaves fine enough to throw back into the lawn as free fertilizer instead of bagging them. Just don’t let a thick layer sit long enough to suffocate the grass.
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Winter: End
Once the growth stops, the clipping should stop as well. Dormant grass – brown and still in the cold or just not pushing new growth – gains nothing from mowing. Rolling a heavy mower over frozen or frozen turf does real damage, breaking the fragile blades and compacting the soil underneath. In most areas the mower leaves for the season and stays there.
The only exception is mild southern lawns. Where the grass continues to creep through the winter, or where a warm-season lawn has been coated with rye for off-season color, an occasional trim keeps things tidy. Cut at the highest end of the row and only when the grass is dry and actively growing. Otherwise, winter lawn care it comes down to staying off the grass and letting it rest.
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How to change the cutting height
Change cutting height to a lawn mower it takes a minute once you find the lever, but it’s pretty much the same on every machine.
On a push mower, such as this Troy-Bilt mower we reviewedis a spring loaded lever on each wheel or on some models a central lever for the entire deck. Press it and pass it through the notches, each at a specified height.
Riding mowers, such as this battery operated lawn tractor we revieweduse a lever or dial next to the seat. Check the manual for which notch is which.
Here’s the overlooked part: height means little if the blade is dull. A blade cut all season becomes blunt and a dull edge rips the grass instead of cutting it cleanly, leaving frayed brown tips with no height adjustment.
A blade scraper from Amazon keeps it touched up at home or a hardware store will grind it for a few bucks. Skip it and you can dial in a perfect height and end up with a ragged, brown lawn.
