Fall
When to Stop Mowing in Idaho: Winterizing Your Lawn
Most people stop mowing too early. First frost hits, mower goes in the garage, done. But the last cut of the season — done at the right height, in the right week — is what determines how your lawn looks next May. More than the first cut, honestly.
Stop when the lawn stops, not when the calendar does
Around here, lawns stop growing meaningfully when we get the first hard frost — usually mid-to-late October in Rexburg, maybe a week earlier in Ashton, a week later in Idaho Falls. Don't put the mower away in September just because it feels right. Look at the lawn. If it's still growing, it still needs a cut.
Last cut: a notch shorter than usual
Aim for about half an inch shorter than your normal summer height. Most Idaho lawns that's around 2.5 inches. Long grass under snow rots and breeds snow mold. Cut it too short and you stress the crown right before winter. Half an inch shorter is the sweet spot.
Get the leaves off before the snow
Leaves trapped under snow for four months smother the lawn and create a buffet for fungus. Whether you bag them, blow them, or hire it out, get them off the grass before the first lasting snow. Same for any debris — branches, the kid's bike, the patio cushions you forgot to bring in.
One last drink, then shut off
Give the lawn a deep watering before you blow out the sprinklers. Going into winter with the soil hydrated helps roots survive the freeze-thaw cycle better than going in dry. Then have your sprinkler system blown out before the first hard freeze — usually mid-October to early November in our area.
Optional: late-fall fertilization
A late-fall feeding (around the last mow) goes mostly to root development instead of top growth. It's the single highest-leverage fertilizer application of the year for a cool-season lawn — which is what every lawn in Eastern Idaho is.
