No Mow May is a campaign that asks people to put their lawnmowers away for the entire month of May, letting grass and wildflowers grow freely to support bees, butterflies, and other pollinators during a critical time of year. The UK conservation charity Plantlife launched the campaign in 2018, and it has since spread across North America and Europe, with thousands of households and dozens of municipalities participating each spring.
Why May Specifically Matters
Early spring is a bottleneck for pollinators. Bees emerging from winter hibernation need nectar and pollen immediately, but most garden flowers haven’t bloomed yet. The small wildflowers hiding in your lawn, things like clover, violets, dandelions, and creeping charlie, fill that gap. They bloom in May if given the chance, but regular mowing cuts them down before they can open.
Dandelions alone are surprisingly important. One study found they produce 9 percent of a lawn’s total pollen and 37 percent of its nectar sugar. That makes them one of the single most valuable food sources in a typical yard during early spring. When you mow them off weekly, that food source disappears.
What the Research Shows
Unmown lawns attract significantly more pollinators than mowed ones. Researchers comparing the two found that lawns left to grow had five times the number of bees and three times the bee species diversity compared to regularly mowed areas in nearby parks. The unmown plots also supported twice as many flowering broadleaf species (22 versus 11), giving pollinators a wider range of food sources.
The nectar payoff builds over time. A study tracking nectar sugar production from late April through July found that unmown grass didn’t meaningfully outperform mowed grass until mid-to-late May, when no-mow plots produced about three times the nectar sugar. By early June, that gap widened to an eightfold difference. This is one reason some ecologists suggest extending the pause on mowing into June and beyond rather than stopping sharply on June 1.
What Grows When You Stop Mowing
Most people expect a wild meadow to appear. The reality is more modest but still valuable. In a typical lawn, you’ll see clover, violets, dandelions, and heal-all pop up among taller grass blades. If your lawn has been treated with herbicides for years, fewer wildflowers will be present at first. Stopping herbicide applications and letting these small flowers establish, or even seeding clover into your grass, creates what’s sometimes called a “flowering lawn” that benefits pollinators year after year, not just in May.
Cool-season grasses like Kentucky bluegrass and red fescue will also grow vigorously and may flower themselves. The lawn will look shaggier than usual, typically reaching 6 to 12 inches depending on your soil and rainfall, but it won’t turn into an impenetrable jungle in a single month.
The Invasive Species Concern
One legitimate criticism of No Mow May is that it lets everything grow, not just the plants you want. A month without mowing can give aggressive non-native species a foothold, particularly in areas where invasive plants are already present in the soil seed bank. Goutweed, for example, is one invasive that mowing actually helps keep in check.
The practical advice from ecologists is to participate but stay observant. Walk your yard periodically and note what’s coming up. If you spot aggressive spreaders, pull them before they set seed. The goal isn’t to abandon your lawn entirely. It’s to give beneficial plants a window to bloom and feed pollinators, then resume management with a better understanding of what’s growing in your yard.
How Cities Are Getting on Board
One barrier to participation has been local weed ordinances. Many municipalities enforce grass height limits, sometimes as low as 6 or 8 inches, with fines for violations. Homeowners who wanted to participate risked citations from code enforcement.
That’s changing. In January 2023, the Eau Claire, Wisconsin city council amended its weed ordinance to push the enforcement start date from April to June 1, giving residents a full month to let their lawns grow without penalty. All participating properties are required to bring their grass back into compliance by June 1. Dozens of other cities across the U.S. have adopted similar temporary suspensions, some requiring residents to register and others simply pausing enforcement citywide.
Getting the Most Out of It
If you want to try No Mow May, a few small steps make a bigger difference than simply ignoring your mower. First, skip the herbicide treatments in spring. Weed killers eliminate the exact wildflowers that pollinators depend on. Second, when you do resume mowing in June, raise your mower blade to its highest setting for the first cut. Scalping a tall lawn in one pass stresses the grass and destroys any remaining flowers. Gradually lowering the height over two or three mowings is easier on both the grass and the insects living in it.
For longer-term impact, consider adopting a “mow less” approach year-round rather than treating May as a one-time event. Mowing every three to four weeks instead of weekly allows short wildflowers to complete their bloom cycles repeatedly throughout the growing season. The research consistently shows that reducing mowing frequency, even modestly, produces measurable gains in nectar availability and pollinator visits that a single month off can’t match on its own.