Most people mow on a weekly rhythm because that is when they have time, not because the grass asked for it. Growth is not constant: it barely moves in February, doubles in May, stalls in a August drought and picks up again in September.
What follows is a rough calendar for a temperate climate and cool-season grasses — the ryegrass and fescue mixes common across northern Europe, the UK and the northern United States. Adjust it by a few weeks for your own conditions rather than treating it as gospel.
The rule that outranks the calendar
Never remove more than a third of the blade height in one cut. Everything below is really just an estimate of how long your lawn takes to grow that third back.
March – April: waking up
The first cut of the year comes when the soil warms past roughly 6 °C and growth restarts, usually in March. Set the height high for that first pass — you are tidying, not scalping. Once a week is plenty, dropping the height gradually over three or four cuts.
May – June: peak growth
This is the demanding part of the year. Warm soil, long days and spring rain can add a centimetre in two days. A weekly cut here breaks the one-third rule almost every time — which is exactly why lawns look worst in the month people assume they look best.
Twice a week is the manual minimum. A robot mower running daily is doing something different in kind: it is taking two or three millimetres at a time, which the grass barely registers.
July – August: heat and drought
Growth slows, sometimes to nothing. Two things change. Raise the cutting height — longer grass shades its own roots and holds moisture. And stop mowing a lawn that has gone dormant and brown; cutting a stressed lawn is how you lose it.
If you run a robot mower, drop from daily to every second or third day and raise the deck. Do not leave a summer schedule running through a heatwave on autopilot.
September – October: the second growth window
Cooler nights, autumn rain and warm soil give a second flush that surprises people every year. Go back to a spring frequency for four to six weeks, then taper.
This is also the best window for repair work — scarifying, aerating, overseeding — because the grass has time to establish before winter.
November – February: winter
Growth mostly stops but does not always stop entirely; a mild winter can need an occasional tidy on a dry day with the height raised. The rules are: never cut frosted grass, and never drive a machine over waterlogged turf. Both cause damage that takes until spring to grow out.
Otherwise, dock the mower, clean the deck, and let it rest.
Setting a robot mower against this
The mistake is to configure a schedule in April and never touch it again. Four adjustments a year is all it takes:
- Spring: daily, height coming down gradually.
- High summer: every two to three days, height up.
- Autumn: back to daily for the second flush.
- Winter: off, or occasional dry-day passes.
If your lawn is split into zones, the shaded areas usually want one step less frequency than the sunny ones. That is the whole benefit of zoning — the front lawn and the strip behind the shed are not the same lawn, and there is no reason to mow them on the same rhythm.
