The Case for Mowing Less: How Science Supports Lazy Lawnmowing
Susannah Lerman had always heard that manicured American lawns were “ecological deserts,” providing approximately the habitat quality of a parking lot. But about 15 years ago, she witnessed something that made her reconsider.
Her husband had just mowed their lawn, but he had left a few patches untouched, as if he had intentionally steered around something. When she went out to investigate, expecting to find kids’ toys or other lost items blocking the mower’s path, she only found flowers — and they were buzzing with bumblebees.
“I started thinking: if we mow our lawns less, do we have more lawn flowers, and if we have more lawn flowers, do we have more bees?” Lerman, a research ecologist with the U.S. Department of Agriculture’s Forest Service, says. She would go on to conduct the first study on lawn mowing frequency to test how bees responded — demonstrating that even small tweaks to how we manage our lawns can make a difference.
Today, the idea that lawns are about as good as pavement still exists in environmental circles, but word is getting out that that doesn’t have to be the case. Thanks to the work of Lerman and other ecologists over the past decade, we now know the truth about lawns: that with the right interventions (or lack thereof), the right kind of lawn can be a great place to support your local pollinators.
Science Says: Slow Your Mow
Lerman’s experimental lawns were supporting way more bees than anyone would have expected: Over the two growing seasons of the test, in just 16 suburban yards, Lerman’s team collected over 4,500 bees of 93 different species — representing over a fourth of the species known to Massachusetts and including one species that hadn’t been recorded in the state for a century. The flower diversity, too, surprised the researchers: 60 different flower species.
Most importantly, she found that an intermediate mowing cadence was best for the bees — in her area, that meant mowing every two weeks. Lawns mowed every three weeks had up to 2.5 times more flowers than one- or two-week yards, but maximum flowers didn’t translate to maximum bees. The reason why likely had to do with the height of the grass with respect to the flowers.
“Most of the bees that we observed in these lawns are about the size of a grain of rice,” Lerman explains. “We think that even though there are more flowers in the three-week lawns, the height of the grasses makes it more difficult for the bees to actually access the flowers, so it’s not as optimal.”
Lerman has continued her research on urban ecology, and more and more researchers have joined in, asking questions about how we can best provide habitat through our yard management decisions. In 2022, a team of researchers in Germany published a meta-analysis, compiling as many studies and datasets as they could find into one big analysis. They found that across dozens of studies, reducing mowing frequency increases both the abundance and species diversity of bees and butterflies, as well as other insect groups like grasshoppers and crickets. Interestingly, they found a consistent decrease in species considered pests, like centipedes, millipedes, spiders, ticks, and mites — these creepy-crawlies were much more common in highly manicured lawns.
“Urban spaces, if managed correctly, can be such important refuges for pollinators and wildlife in general,” explains Sean Griffin, director of science and conservation at the Lady Bird Johnson Wildflower Center. “They can actually provide some of the best remaining habitats, since they’re free from the pesticide pressure from agriculture you find outside a lot of cities.”
Millions of Acres
These research findings reveal a huge opportunity for positive ecological impact with minimal — well technically, with less — effort. Lawns are incredibly prolific in the United States, where there are an estimated 50 million acres of turf — twice the land area of the National Parks in the Lower 48, or about the size of Illinois. It’s not just the lawns in our yards, but also those within parks, around office buildings, and more.
When you picture a lawn, your mental image might be of a perfectly groomed one: a luscious green monoculture with no other life in sight. But the average lawn isn’t manicured to perfection. In Lerman’s study, she aimed for average — choosing lawns for her experiment that were not meticulously kept, but not surrounded by pollinator gardens, either.
“It can surprise you that there’s biodiversity lurking in these unexpected places,” Lerman says. “It’s important to recognize that your efforts don’t have to be perfect to still be good enough. I think that’s what this research shows.”
Mowing in Native Grasslands
Even in certain natural systems, like grasslands, the right amount of mowing can be beneficial. At the Wildflower Center, researchers have studied prescribed burning and mowing at different seasons and frequencies for the last 25 years in a long-term ecological experiment.
Much like in your yard, they’ve found that mowing at the right time and frequency can actually increase plant diversity. For maximizing floral diversity, fall mowing was best. And although the mowed area isn’t as good as a fully restored ecosystem, that’s OK — the goal here is to give an ecological boost to the systems we already have. Making smart mowing decisions is a great way to do that.
Lawn People Need Not Apply
Lerman was happy to concede that some people are just “lawn people,” and it’s okay if “slow your mow” isn’t for everyone. And honestly, if you’re on the opposite end of the spectrum, already converting your lawn to one giant wildflower garden, by all means, continue. The “slow your mow” movement is for the vast majority of people who fall in-between — and Austin is a perfect place for this movement to take root.
“When I first moved to Austin, I was really surprised and happy to see that there’s already a big cultural movement here toward using native plants and reducing water,” says Griffin. “There’s a big emphasis in general on green spaces and sustainable yards.”
Although Lerman’s study was done in Massachusetts, her findings apply in areas with different plant species and climate. Instead of dandelions and clovers, your lawn might have more straggler daisies and henbits. But the key is not in the exact frequency (two weeks, in Massachusetts), but in achieving the same structure: Let the flowers bloom as long as possible, but once they’re drowning in grass, it’s time to cut.
And there’s good news for people that like the look of a tidier lawn (or have active homeowners associations): Lerman said that, anecdotally, the two-week lawns didn’t look bad at all, only that they “needed a trim.” Only the three-week lawns tended to look more unkempt, but those weren’t best for the bees, anyway.
By the way, if you’re worried that letting your lawn go for an extra week will land you a citation from the city, don’t be: City of Austin code requires residents to keep lawns at a maximum of 12 inches (30 cm), double the height of even the 3-week lawns in Lerman’s study.
So the next time you’re feeling lazy about lawn mowing, know that science is on your side, and let the flowers bloom.
“People don’t realize that they can actually make a difference,” says Lerman. “Just mow less. Anybody can do it. It doesn’t cost anything. You don’t have to do something. I think that resonates with people. Your lawn already has all it needs to be a wildlife habitat.”