By: Carl Schimenti, Urban Environmental Scientist, Cornell Turfgrass Program
Any time autonomous mowers are brought up in conversations with turf professionals, there is an undercurrent of hesitation given the climate around labor and job replacement. While this is a primary discussion point, I’d like to separate that out for a moment, and relay what people are learning about how the grass reacts to these mowers, compared to
traditional mowing regimes.
Auto-mowers are altering the morphology of the grass, leading to greater tiller density and shoot density compared to traditional mowing, on both tall fescue and kentucky bluegrass (Grossi et al., 2016; Macolino et al., 2025). Practically, I read this as “improving turf density”. I would mainly attribute this to the mowing frequency of the robots, which is daily. What immediately comes to mind is the practicality of this on high-traffic athletic fields. If you’re only able to mow once or twice per week, that is “leaving density on the table” so to speak. And you don’t have to take it from a desk jockey like me. Aaron Ramella, Director of Grounds for the Buffalo Bills, mentioned increasing the mowing frequency in a recent NYSTA webinar as a core principle of improving fields.
I would expect that the amount of organic matter accumulation (thatch) would increase with the robots, as a function of the increased turf density created and the lighter weight of the unit reducing compaction. However, in a recent study, thatch depth in the auto-mower plots was significantly less compared to traditional 1x per week mowing (Grossi et al., 2016). That’s an interesting finding, given that facilities that have adopted autonomous mowers have reported softer surfaces. I suspect that thatch depth is not entirely correlated with thatch density (OM246 value), which may explain the “feel vs. real” dissonance here. Do auto-mowers produce shallower, but more vigorous thatch? Hmm…. maybe an opportunity to do some more rolling!
The prevalence of weeds is likely to change under the auto-mower regime. It appears that creeping-type weeds (clover, birdsfoot trefoil) may be able to persist, and even thrive, under auto-mowing regimes in tall fescue (Pirchio et al., 2018). But there is also evidence that auto-mowers can control weeds, even the same birdsfoot trefoil, in warm-season grasses (Galiardi et al., 2024). At this point, it’s not entirely clear which situations might benefit the most in terms of weed control from auto-mowing. A question for Dr. Matt Elmore, during our May 9th Turfshow.
I’ll end with one final thought. I’ve enjoyed the conversation auto-mowers have created, because it brings us all back to the most fundamental thing about turfgrass: MOWING. It’s easy to get sidetracked by the minutia and peripheral aspects of turf management, but sometimes, it’s nice to “keep the main thing, the main thing”. That is one thing auto-mowers have been very effective at!