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From an ecological point of view, lawns suck. We use up water, waste fuel on mowing, and spread too much fertilizer & herbicide to create a monoculture that’s of use to almost nothing. Although I admit that a green well trimmed lawn looks awesome, perhaps because humans evolved in African plains and it resonates with some ancestral memory or perhaps because lawns are a reflection of wealth or perhaps for some other reason, like croquet.

So what to do if you have a lawn and want to limit ecological damage without actually abandoning it and making your neighbors hate you? Accept the presence of weeds, of course – “They’re not weeds, they’re biodiversity” does a pretty good job of shutting up the Neighborhood Naggers – but also mow less often. Every other week, to be precise. Not every week, not every third week, but every other week.

That seems suspiciously precise, but it’s a finding from a study that I read about in CleanTechnica (article is here) done by folks at UNH, UMass and other institutions.

The scientists counted yard flowers — decorative flowers that homeowners avoid when mowing— and lawn flowers — weedy plants that are the target of lawnmowers. Researchers also measured average grass height and counted and identified bees. Lawns mowed every three weeks had more than twice as many weedy flowers as those mowed more frequently. Lawns mowed every two weeks, on the other hand, had the greatest number of bees, but less diversity among bee species than the other two intervals.

This finding surprised scientists, who had assumed that the longer time between mowing, the better it would be for bees. They speculate that bees have a tougher time reaching the flowers when the grass is very high. “We thought that the number of bees would match with the number of flowers,” she said. “However, the three-week yards had a lot more flowers, but also taller grass. For some of the really small bees — about the size of a grain of rice — it might have been too much effort to get to the flowers. And these small bees really dominated our study.”

So there you have it. Mow your lawn biweekly – in the every-other-week sense of that incredibly confusing word, not the twice-per-week sense.

And now, to complicate things: This is the exactly opposite of advice for avoiding Lyme disease-carrying ticks. To limit those beasts you want to mow frequently and keep the grass short, because that allows in more sun and heat. Ticks are flat and dry out easily, so they’ll burrow down to avoid the sun, which means they can’t grab onto you as you walk by.

I frequently mow a few places where I walk regularly, like between the door and the car, and out to the rain gauge that I measure daily, and let the rest of the yard go. I use a battery-powered mower, which is much nicer (quieter, starts instantly, no stinky gas cans, you can flip it over to clean out grass without spilling fluids).


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