How-to Guide
When to Stop and Start Mowing the Lawn
The short answer
Fall: keep mowing as long as the grass keeps growing. Iowa State Extension's marker for cool-season lawns (bluegrass, fescue, ryegrass) is that foliage growth stops when daytime highs are consistently below 50°F, which in Iowa means late October or early November. From mid to late September, lower the cutting height from 3.0-3.5 inches to 2.5-3 inches so the lawn does not go into winter long and matted, which invites snow mold under leaves and snow. Once growth stops, the mower goes away; there is no need for a scalping 'final cut'.
Spring: the trigger is height, not a date. Set the mower at 3 to 3.5 inches and mow the first time the grass reaches about 4.5 to 5.25 inches, so you obey the one-third rule: never remove more than one-third of the leaf blade in a single mowing. Warm-season grasses (bermudagrass, zoysia) simply follow growth: they brown into dormancy after frost and are mowed again once they green up and reach mowing height; your regional Extension calendar gives local dates.
The one-third rule governs every mow at both ends of the season; cutting deeper than that stresses turf and piles up clippings.
Fall: the last-mow sequence
- 1Mid to late September — Lower the mowing height from 3.0-3.5 inches to 2.5-3 inches for cool-season lawns.
- 2October — Keep mowing on the one-third rule as growth slows; mowing also chops fallen leaves, which must not mat on the lawn over winter.
- 3When highs stay below 50°F — Cool-season top growth stops. In Iowa, bluegrass usually quits in late October or early November; your latitude shifts the date.
- 4Done — Once growth has stopped, put the mower away. Going into winter at about 2.5 inches, unmatted and leaf-free, is the snow-mold-resistant finish.
Spring: when to make the first cut
There is no correct start date, only a correct height. Iowa State's spring guidance: set mowers to cut at 3 to 3.5 inches, and start mowing once the grass reaches 4.5 to 5.25 inches so no cut removes more than one-third of the blade. Removing more than a third in one pass stresses the turf and dumps heavy clippings that can smother the grass below.
Resist mowing extra-short in spring; mowing at the low end of the range repeatedly weakens roots into summer. If the lawn got away from you and is very tall, bring it down in stages over several mowings, one-third at a time.
Warm-season lawns
Bermudagrass, zoysia, and other warm-season grasses run the opposite calendar: they grow through summer heat, brown into dormancy after fall frost, and green up in late spring. Mow while they are actively growing and stop when growth stops with dormancy; resume in spring once the lawn has greened up and reached its mowing height, still on the one-third rule. Exact months vary by region and species, so use your state Extension's lawn maintenance calendar rather than northern dates.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Iowa State University Extension - Late Summer and Fall Lawn Care — Cool-season grasses stop growing when daytime highs are consistently below 50°F, late October or early November in Iowa; lower mowing height from 3.0-3.5 inches to 2.5-3 inches in mid to late September; continue mowing until growth stops; never remove more than one-third of leaf area.
- Iowa State University Extension - Mowing Tips for Spring — Set mowers at 3 to 3.5 inches and begin spring mowing when grass reaches 4.5 to 5.25 inches so no more than one-third of the blade is removed in a single mowing.
- University of Missouri Extension - Turfgrass Disease Control (G6756) — Snow mold develops at 32-45°F under the high humidity found beneath melting snow, leaves, mulch, or heavy thatch — the reason for stepping mowing height down and clearing leaves before winter.