In May, you can mow the grass – the best way to facilitate pollinators is to plant native plants

The idea is basic: stop mowing your lawn in May so that lawn flowers like dandelions and clover can grow and provide a food source for bees and other pollinators.

The No Mow May campaign was launched in 2019 by Plantlife, an environmental charity based in the UK, in response to the well-documented loss of grasslands and the alarming decline of native plants and animals. It has since been taken up by many North American gardeners and environmentalists.

Studies have shown that many flowers growing on unmown lawns in the UK Down support british pollinators. However, North America has completely different ecological communities, composed of unique flora and fauna.

If you want to support pollinators, it’s critical to consider the ecological context of your yard — and #NoMowMay may not be an effective strategy. entomology researchers Who run programs on pollinatorswe see better ways that North Americans can facilitate pollinators thrive in their gardens.

What grows on lawns in North America?

The most common lawn flowers in North America are not native to the continent, but were introduced here from Europe and Asia. Many of them, such as bull thistleare noxious weeds that can crowd out native plants and contribute to problems such as soil erosion. Others such as common ivyare aggressive, invasive weeds in natural areas.

Allowing these weeds to grow can enhance their numbers in the landscape and potentially reduce native biodiversity by creating near monocultures. Not mowing the lawn and allowing these plants to spread can cause weed problems that neighboring properties will likely have to deal with with herbicides.

Pollinators can be found on lawn flowers, but looks can be deceiving.

Some non-native lawn plants are very attractive to pollinators. Thistle, crown vetch, and, to a lesser extent, dandelion and white clover are commonly visited by bees. This attractiveness helps invasive plants pollinate, produce seeds, and disperse effectively.

But the pollinators you see on these non-native plants are already the most common in the landscape. Adding these plants to the landscape does not improve North America’s pollinator community or support biodiversity.

The dominance of a few pollinator species on these plants may indicate that human influence has reduced the number of species in this ecosystem. Typical human-altered landscapes have miniature numbers of cosmopolitan weeds—species that occur in a wide range of habitats in many parts of the world—and a handful of pollinator species.

For example, a 2014 study of urban and suburban lawns in Kentucky found that 90 percent of the spring insects visiting dandelion beds there were members of a single bee species, foreign honey bee; one species of butterfly, common brand captain; and a few species of hoverflyHoneybees accounted for almost 50% of pollinators visiting white clover in spring, followed by hoverflies and several species of bumblebees.

The surrounding landscape also plays a role

Few home gardens are immense enough to support pollinator populations. A dandelion patch in a city district dominated by steel and concrete would seem like a pollinator’s paradise, simply because there would be nothing else nearby for bees to feed on. But very few bees would visit dandelions, and those would be bee species that are as common across the landscape as most of the birds in the area are pigeons or house sparrows.

In a nature reserve, the same dandelion meadow would attract a more diverse community of pollinators. But it would still be dominated by common generalists that visit many types of flowers and are not very picky. When more specialized pollinators appear in yards, they spill over from neighboring landscapes that do not include lawn plants.

A 2016 study found this pattern on suburban lawns in Springfield, Massachusetts. The researchers collected 5,331 bees from 111 species flying around miniature suburban plots over a two-year period. Only 13 species were represented by 4,442 individual bees they collected, while 81 species were represented by 10 or fewer individual bees.

Plant a variety of native plants

Rather than stop mowing and allow non-native plants to dominate your spring landscape, we recommend planting a variety of native trees, shrubs and flowering herbaceous plants.

Native North American plants and pollinators have evolved together over time. Plants have characteristics that allow for specific interactions, the right flowering times, and the right type of nectar and pollen for specific native insects.

Penn State scientists Pollinator Research Centerwhere we both work, examined pollen collected by wild bees and honeybees to see which plants provided the most nutrients for the bees. They found that in April and May, flowering trees—including maple, oak, and willow—provided the most pollen for the bees.

Other native North American plants that are visited by pollinators, such as bellflowers, aquila, and phlox, have evolved to grow in partial shade while trees develop leaves above them.

More reasons to mow

Leaving grass uncut in May or June is also problematic because it creates a favorable habitat for ticks and wildlife, such as deer and rodents, which carry ticks. This can enhance the local risk of tick infestations and tick-borne diseases.

Keeping grass shorter creates a drier environment that is unfavorable for ticks. It also limits wildlife habitat and food sources, which reduces tick populations.

Finally, allowing weeds to grow in unmowed lawns can cause conflicts with neighbors. Whether it’s for aesthetics, local property values, or public health, many cities have ordinances that set lawn height limits and will residents who do not comply with the regulations are punished.

While we agree that mowed lawns don’t provide much food or support for native species, skipping mowing for a miniature period of time doesn’t do much either. Pollinators need plants in bloom throughout the growing season, from early spring through winter.

We recommend transforming your garden into a true pollinator haven, adding native plants and flower beds over time and potentially transforming your entire lawn into a garden. For a list of North American pollinating plants that are native to your region, visit Xerces Society AND Pollinator Partnership. State Master Gardener groups also have detailed information on creating pollinator gardens in your area, such as the Pollinator Garden Certification Program with Penn State Master Gardeners.