Robotic mowers are really good now

Photo: Simon Hill

Light Detection and Ranging (LIDAR): This system, which is also used by self-driving cars, fires rapid laser pulses to map a 3D terrain. It enables mowers to cut grass under thick tree canopies or near tall buildings where GPS signals typically fail.

Artificial intelligence vision: Some mowers now use cameras to recognize grass areas, boundaries and obstacles. Robotic mowers with AI vision can avoid stray footballs, cats and other critters, and maybe even pet messes. But they can also be very sensitive, stopping at fallen branches, leaves or overhanging plants.

Some of the best mowers, like the Mammotion I’m currently testing, use a combination of the latter three technologies to precisely map and cut areas, reliably navigate to and from a charging dock, and avoid unexpected obstacles. None of them are guaranteed. My top pick chewed up a vacuum paddling pool, but if you set the sensitivity too high, it left areas uncut.

In addition to finding their way around, many of the latest robotic mowers are designed to handle rough terrain. Not too rough, but suitable for a rugged garden or yard with steep slopes. Some models come with interchangeable tires, so you can use sturdier wheels when you need them. But it’s important to check the terrain and slopes your mower can handle in advance. Four-wheel or four-wheel drive mowers are best for handling steep or uneven terrain.

Cutting edge

Traditionally, robotic lawnmowers have been very bad at cutting right to the edge of your lawn. Most of the early robotic mowers I tested left thick borders of uncut grass, up to a foot wide. I don’t think this problem has been completely solved, but some newer models have counterbalanced blades located close to the edge of the mower, or have an overhang section that extends beyond the wheels, so that it can cut right to the edge when the robotic mower is turning. There are also robot mowers with built-in trimmers and other garden tools, although I haven’t tested those yet.

While edge cutting is improving, I still find that most robotic lawn mowers need some adjustment to reliably cut the entire lawn. I often have to adjust the map or adjust the sensitivity to make sure it hits the edge, yet there are still areas that it seems to miss. Plants, shrubs and trees overhanging the lawn cause problems, with robotic mowers, understandably, erring on the side of caution when it comes to potential snags. There is still room for improvement here.

Smart finishing touch

Husqvarna app via Simon Hill

While the first robot mower I tested turned my lawn into a muddy mess, most robotic lawnmowers now have some form of rain detection, so you can set it to not cut if the grass is wet. The latest models are also much better at handling wet grass and keeping it from slipping or moving much of your lawn.

Some robotic lawn mowers offer customization in terms of the lawn finish you want. You may find an option in the app for Wimbledon lines (dark and light lines), which is achieved by cutting rows in opposite directions. Some mowers can also create spirals, checkerboards, and other patterns.