It’s that time of year again: “No Mow May,” the annual initiative that discourages residents in Michigan and around the globe from mowing their lawns to promote a diverse habitat for bees, butterflies and other pollinators.

The idea is that, by letting clovers, dandelions and other weeds grow, pollinators will have nectar and pollen to feed off, supporting various species. And residents could save money on their water bills in the process.

But, there’s a catch: There is very little evidence that shows letting your grass grow for just a month is beneficial to pollinators at all, said David Lowenstein, a consumer horticulture expert for Michigan State University.

“The problem with just not mowing your lawn, is you’re not providing all the ingredients that the bees need for food,” Lowenstein told Bridge Michigan.

“Some weeds like dandelions aren’t as nutritious for bees as other flowers that might be blooming in the spring, and a lot of the flowers that bees use in the springtime actually grow more as shrubs or trees.”

No Mow May has also proven controversial in communities that don’t embrace it. Lansing, for instance, last year reportedly sent more than 1,400 overgrown grass notices to residents.

Still, the movement has champions across the state — and world.

The British botanical charity Plantlife began promoting No Mow May in 2019 as a way to “provide a feast for pollinators, tackle pollution, reduce urban heat extremes and lock away atmospheric carbon below ground.”

The group asserts that letting a small patch of grass grow longer not only helps pollinators but “provides shelter for small mammals.”

Several local governments in Michigan have embraced the movement.

Ferndale began participating in the initiative last year after residents asked for it in 2022. An environmental sustainability commission recommended that the city council adopt a resolution to suspend the city’s mowing regulation during the month of May. The Oakland County suburb otherwise prohibits residents from letting their grass grow beyond 7 inches.

The initiative has ancillary benefits, according to Ferndale officials: Mowing your yard compacts the soil, but letting it breathe through May can help improve stormwater infiltration.

“We care about our ecosystem. We care about having native plants. We care about stormwater infiltration and removing as much stormwater from the system as possible, and we are committed to sustainability,” said Logan Applebee, Ferndale’s zero waste manager.

“Everyone is welcome to participate in whatever way they see fit, but that’s why it’s a beautiful program,” Applebee said. “…You don’t have to participate fully in this, but mow fewer times than you might, or mow it to a taller height, which supports the root systems and supports ecosystems and allows for more of those flowers.”

In Washtenaw County, Ann Arbor has also embraced a form of No Mow May for two years now. This year, officials modified the program to better meet the needs of residents who participated, and those who did not.

The city’s “Pollinator-aware yard care” program suggests residents “reduce how often they mow and keep their grass at a higher height, but then also has other suggestions on ways that folks can do lawn care or landscaping that is supportive of pollinators,” said Sean Reynolds, senior analyst for Ann Arbor’s Office of Sustainability and Innovations.

Residents participating in the initiative will not be fined for having longer grass during the month of May. During the rest of the year, however, Ann Arbor residents are prohibited from having grass that exceeds 12 inches and “other ground cover vegetation” that exceeds 36 inches.

“That was one of the main things that we heard positive feedback around, was that this is really great for providing benefits to pollinators, providing food for pollinator species,” Reynolds said.

However, there were many residents who were concerned about grass heights and how they could create an environment for ticks, mosquitoes and other unwanted pests, Reynolds said.

According to a survey conducted by the city following last year’s campaign, over 53.5% of people surveyed expressed concern about ticks, mosquitoes and the risk of disease.

Residents who don’t mow their lawns for a month are creating an environment that is welcoming to ticks, but that doesn’t necessarily mean there will be an infestation, said Lowenstein, the Michigan State expert.

“Once you mow your lawn again, that grass is going to be low to the point that you’re probably not going to have ticks there,” he said.

Bees also need shelter, and the weeds that grow from not mowing your lawn for a month aren’t the ideal home for bees, Lowenstein said.

“Bees either nest in the ground or they nest in cavities,” he said. “Leaving your lawn high isn’t going to have any effect on the nesting part of it.”

Not mowing your lawn in May means less work for homeowners that month, but it also makes it more difficult to mow and maintain your yard in June, Lowenstein added.

Instead, he suggests planting flowers or shrubs that bees like in a small area of your lawn and leaving it undisturbed, creating a flowering bee lawn or planting wildflowers in part of your lawn that bloom throughout the season.