Robot mower cutting height: every model, every grass

Set a robot mower to your grass's height, not to whatever the mower happens to reach. Tall fescue wants 3–4″, Bermuda 1–2″, and most lawns sit somewhere between. The mower's deck range decides whether it can get there — and that's where models really differ. Below: the range of every robot mower we sell, checked against the right height for 11 common grasses.

What is each robot mower's cutting-height range?

Published deck ranges, verified against manufacturer and retail listings. Models that share a deck share a row. A model without a range we could verify is left out rather than guessed.

Which mower reaches your grass's height?

Each row is a grass and its ideal maintained height. ✓ the deck covers the whole zone, including the seasonal moves; ◐ it reaches part of it; ✕ it can't get into the zone at all. Tap a mark for the full fit check where we've written one.

Tall fescue — the Mid-Atlantic workhorse and the grass we map most — is fully covered by: Navimow X430 · X450 · Terranox 120 · Terranox 240, Mammotion LUBA 3 5000H and Yarbo Y40 Pro · Y40P Pro.

What does "partly" mean for my lawn?

A top-clipped deck reaches into your grass's zone but stops short of its top — fine most of the year, but a cool-season lawn wants to ride that top through July and August, when taller blades shade the roots. A bottom-clipped deck can't take the grass as short as some owners like; for Bermuda or Zoysia that's the difference between a golf-course look and a perfectly healthy but softer lawn. Neither is a deal-breaker. A ✕ is: the mower would keep the grass permanently outside the height it grows best at.

The one split that catches buyers out is the Mammotion LUBA 3 AWD 5000: the standard deck suits warm-season grass, the high-cut 5000H suits cool-season grass, and they're sold as separate models. Order by your grass.

How do I lower or raise the cutting height safely?

In steps. The rule underneath every mowing decision is the ⅓ rule: never take more than a third of the blade in one cut. Dropping a 4″ lawn straight to 2.5″ breaks it, and the lawn goes brown for a week. Move the setting a quarter to half an inch at a time and let the robot work at each step for a few days. Raising is always safe — do it before a heat wave, not during.

Height also moves with the year: highest for new grass and summer, the middle of the range in spring and fall growth, a notch lower for the last cuts before winter. The schedule by season lays out the months, and how often to mow covers the rhythm that goes with each height.

Can a robot mower handle tall or overgrown grass?

It keeps a lawn at height; it isn't designed to recover one. A robot takes a few millimetres a pass, every day or two — that's the whole point. If the lawn has grown well past the top of the deck range (after a vacation, or at the first spring cut), mow it down once with a conventional mower and let the robot take over from there. The same goes for new grass: the first cut comes late and high, covered in mowing new grass with a robot mower.

Keep reading

• Robot mowers by grass type — the right height for every common grass, and why.
• Why does my lawn look brown after mowing? — the ⅓ rule and blade care.
• Navimow blade replacement — how often, how to, and the new-screws rule.
• Robot mower not cutting evenly? 7 fixes
• How to make stripes with a robot mower