Mow every 4 days or every 7? Why the answer depends on which US state you're in
The UK version of Turf Alert uses a single national mow interval, scaled by cut height, that holds up fine across the whole country. Applying that same single number to the US broke — not everywhere, but badly in some places.
What "broke" actually looked like
The target, in both markets, comes from real-world convention: a 7-day median gap between mows, with roughly a third of gaps landing under a week (the "vigorous growers cut every 4-5 days" case, as the minority, not the rule) — for the UK, this is checked directly against RHS guidance and an 86-year backtest; for the US, it's checked against a real dataset of 50,000+ actual mowing appointments, where "for steady, full-season customers, mowing usually lands right around every 7 days" is the converged standard, alongside university extension guidance pointing the same direction.
Using the UK's single interval value against US cities found Minneapolis and New York City at 51-53% of gaps under a week — nearly as far from the 34% target as the UK's own interval was before its fix. Meanwhile Denver and Salt Lake City were already sitting at just 5-12% under a week, well under target in the other direction. No single number fits both: the US cool-season zone spans far more climate diversity than one country's national interval was ever built to handle.
The fix: one value per state
Each covered state's interval was independently grid-searched (3.0 to 7.0 days, in 0.25-day steps) against its own 86-year cached backtest, for the value closest to that same 7-day-median, 34%-under-a-week target — never guessed or interpolated from a neighboring state.
- Utah (Salt Lake City): 3.50 days
- Colorado (Denver): 3.75 days
- Oregon (Portland): 3.75 days
- Washington (Seattle): 3.75 days
- Missouri (St. Louis): 4.25 days
- Illinois (Chicago): 4.50 days
- Michigan (Detroit): 4.50 days
- Massachusetts (Boston): 4.75 days
- DC (Washington): 4.75 days
- Minnesota (Minneapolis): 5.00 days
- New York (New York City): 5.00 days
- Pennsylvania (Pittsburgh): 5.50 days
The spread is real, not noise: Utah's 3.50-day interval and Pennsylvania's 5.50-day interval are more than half a week apart at the extremes — Pittsburgh alone ran 67.1% of gaps under a week at the shared starting value of 4.0 days, well past even Minneapolis and New York's problem numbers, before its own dedicated grid search brought it down to 5.50 (29.0% — the closest available point to target before the curve falls off a cliff toward zero).
What drives the difference
Growth potential, and by extension how often a lawn genuinely needs cutting, tracks each state's own climate — Utah and Colorado's drier, higher-elevation growing conditions produce a meaningfully different real-world mow rhythm than Minnesota's or New York's. Applying one national average erases exactly that difference, which is what actually broke when the UK's single value was tried here first.
What this means for you
If a generic app or calendar tells you to mow weekly regardless of where you live, it's giving you the Minnesota answer whether or not you're actually in Minnesota. Turf Alert tracks growth day by day for your own city and applies the interval that's been checked against your own state's climate — not a borrowed national average.
See your city's current mow status on the forecast page, or sign up to get told when your own lawn — not a generic weekly clock — is actually due.
Feed timing got a similar US-specific correction — see why the UK's feed threshold doesn't work here.