Pick your grass — get the mower deck height, the mow-again trigger, and what taller grass buys you.
Set your mower to
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Mow again when grass hits
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Healthy range for this grass
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Sharpen the blade at least yearly — a dull blade tears instead of cuts, and torn tips brown the whole lawn a shade. Last mow before winter: drop to the low end of the range.
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The mowing math
mow-again trigger = target height × 1.5 (the one-third rule) e.g. kept at 3" → mow when it reaches 4.5"
Height and frequency are one decision, not two: the height you keep sets how tall it can get before the one-third rule says mow. Tall-kept lawns break the rule less often — a lawn kept at 3.5 inches has a full inch and three-quarters of headroom; a lawn scalped to 1.5 has three-quarters of an inch.
Why the tall end wins
Blade height mirrors root depth — grass kept at 3.5 inches roots roughly twice as deep as grass at 2, which is the difference between shrugging off a dry week and browning out. Tall grass also shades the soil: cooler roots, less evaporation (it genuinely lowers the watering bill), and darkness where crabgrass seeds wanted sunlight.
Seasonal adjustments
Summer heat: top of the range, always. Spring and fall: anywhere in range. Final mow of fall: low end, so matted winter grass doesn't invite snow mold. And any week you're also feeding — the fertilizer calculator has the dose — mow first, feed second, water third.
Frequently asked questions
What height should I mow my grass?
By grass type: tall fescue and Kentucky bluegrass are happiest at 3–4 and 2.5–3.5 inches; bermuda runs short at 1–2; zoysia 1–2.5. Within every range, taller = deeper roots, more drought tolerance, and fewer weeds (shade kills weed seedlings). Pick your grass above for your numbers.
What is the one-third rule?
Never cut more than a third of the blade in one mow — cutting deeper shocks the grass, browns the tips, and stalls root growth for weeks. It's the single most broken rule in lawn care, and it sets your mowing FREQUENCY: mow when the grass is 1.5× your target height, however many days that takes.
Should I mow shorter so I can mow less often?
It backfires — scalped grass grows FASTER (it's panic-regrowing), needs more water, and invites weeds into the newly sunlit soil. Counterintuitively, mowing tall is the lazy strategy: slower regrowth, shaded-out weeds, and a lawn that skips a week without drama.
Should I bag clippings or mulch them?
Mulch them (leave them) — clippings are ~4% nitrogen and return about a free fertilizer application per season. They don't cause thatch (that's roots and stems, not clippings). Bag only when the grass got away from you and clumps would smother, or during active fungus outbreaks.