· by Michael Blair, Nashville's Lawn Care
Most people asking about biweekly mowing are trying to save on a visit every other week, and that is a fair thing to want. The trouble is that grass in Middle Tennessee does not grow at one steady rate. Tall fescue races in April and nearly stops in a hot, dry July, and bermuda does the reverse. A schedule that suits the lawn in one month can wreck it in another, so the useful question is less about weekly or biweekly and more about which months can stretch. Our weekly lawn mowing service runs on that question.
The grass sets the schedule
The rule every turf program in the state starts from is simple. UT Extension’s W 1068 lawn and landscape guide says no more than one-third of each leaf should come off in a single mowing. Ohio State’s Lawn Mowing fact sheet, HYG-5816 puts the arithmetic plainly: grass kept at 3 inches gets cut before it passes 4.5 inches. How often the mower has to come is whatever it takes to keep that rule, and the calendar has no say in it.
The same UT guide gives the example that settles most of the weekly or biweekly argument for a fescue yard: a tall fescue lawn might need mowing once a week in April and only once a month in July. That is the same lawn, the same owner and the same mower, with a fourfold difference in how often it needs cutting. A flat biweekly price spread over the season is mowing too often in one stretch and not often enough in another.
When every other week works
Tall fescue in the heat of summer is the clearest case. The W 1068 guide says to raise fescue before hot, dry weather, to the 2 1/2 to 3 1/2 inch range, and to cut it higher for deeper roots. A tall, slow-growing fescue canopy in July often adds less than a third of its height in two weeks, and on clay that has dried out between storms it may barely grow at all. Running a mower over it weekly in that stretch mostly wears tracks into stressed grass, which is part of the story in why a Nashville lawn goes brown every July.
Bermuda at the shoulders of its season is the other case. UT Extension’s 2024 Lawn Calendar tells bermuda and zoysia owners to raise the mowing height by at least half an inch to get ready for winter dormancy, and to stop mowing after frost. Through that slow-down in fall, and before the grass greens up and takes off in spring, a bermuda lawn rarely needs a weekly cut. A droughty stretch in any month, with no irrigation running, can earn a lawn the same allowance.
When biweekly hurts the lawn
Fescue in spring is where biweekly goes wrong. A lawn growing fast enough to need a weekly cut in April will be well past the one-third mark after fourteen days, and the mower then has two bad choices. Cut it back to its normal height and the blades lose far more than a third, which the W 1068 guide calls scalping: the plant draws on carbohydrates stored in its roots to regrow leaf, and those reserves may not be replaced, leaving a shallow, sparse root system going into summer. Ohio State goes further and warns that cutting past the one-third line can severely damage or kill turfgrass.
The second problem is the clippings. Grass left two weeks in a growth spurt throws off a heavy, wet load that a mulching deck cannot chop fine enough, so it drops in rows and clumps on top of the lawn. Those rows shade the grass beneath them and leave yellow stripes a few days later. The UT guide notes that keeping to the one-third rule avoids leaving large amounts of clippings on the surface, which is the same point from the other side. Bermuda in June and July is the warm-season version of this, since that is when it grows hardest and is kept shortest.
Running a biweekly lawn through the year
On a fescue lawn the honest schedule changes with the season. Spring is weekly, sometimes with an extra pass after a long wet week. Once the heat sets in and growth slows, the deck goes up and the visits can drop to every other week, and on the hottest, driest weeks that can be generous. When nights cool in September and October, fescue starts growing again, and the schedule needs to tighten back up through leaf season before it eases off for winter. Our notes on how short to cut grass in Tennessee heat cover the height side of the same plan.
Bermuda runs nearly the opposite way. It needs the tightest schedule from late spring through summer and the loosest in early fall, when the deck goes up half an inch and the visits spread out until frost ends the season. Lawns with both grasses, which is common where an older bermuda yard was overseeded with fescue, have to follow whichever grass is growing faster at the time.
When our crews set up a lawn on an every-other-week plan, we write in the months it will run weekly instead and raise the deck before a long gap rather than after it. If you want a schedule matched to your grass and your yard, ask for a free estimate and tell us whether it is fescue, bermuda or some of each.
Sources
- UT Extension, W 1068 Lawn and Landscape Weed Control for Homeowners — The one-third rule, scalping and root reserves, fescue weekly in April versus monthly in July, mowing heights for hot, dry weather
- UT Extension, 2024 Lawn Calendar (PB 1903) — Raise bermuda and zoysia at least half an inch before winter dormancy; stop mowing after frost
- Ohio State University Extension, Lawn Mowing (HYG-5816) — Mow 3-inch grass before it passes 4.5 inches; exceeding one-third can severely damage or kill turfgrass