UNIVERSITY PARK, Pa. — Many have heard about “No Mow May” — a movement that encourages people not to mow their lawns during the month of May to encourage the growth of flowering plants for bees and other pollinators.
But is it really beneficial?
Penn State News spoke with two pollinator experts in Penn State’s College of Agricultural Sciences — Christina Grozinger, Publius Vergilius Maro Professor of Entomology and director of the Center for Pollinator Research, and Harland Patch, assistant research professor of entomology and director of pollinator programming for the Arboretum at Penn State — about the best ways to help pollinators and encourage biodiversity.
Q: We thought No Mow May was good for our environment — is it not?
Patch: This was a campaign started in the United Kingdom to “provide a feast for pollinators,” which sounds like a good idea but doesn’t help pollinator populations here in Pennsylvania.
Most lawn flowers are not native to North America. Many are noxious weeds, like bull thistle, and others like ground ivy are aggressive and invasive. It’s true that some of these non-native lawn plants — such as crown vetch, dandelion and white clover — are attractive to pollinators. But this attractiveness also helps these invasive plants set seed and spread, and allowing these weeds to grow can increase their numbers and drive down biodiversity by replacing native flowering species.
Q: Won’t these flowers still help pollinators, native or not?
Grozinger: The pollinators you see on these non-native plants are already the most common in the landscape. So, adding these plants to a landscape does not improve native pollinator communities or broaden biodiversity.
Also, the Penn State Honey and Pollen Diagnostic Lab conducted studies that examined the pollen that wild bees and managed honey bees collected throughout the year to see which plants were providing the most nutritional resources for bees.
We found that in April and May, flowering trees — not lawn weeds — provided the most pollen for bees. These trees include maple, oak and willow, as well as pear, apple and stone fruit trees. From the middle of June and into fall, bees mainly collected pollen from flowering perennials, shrubs and vines.
Q: So, what can people do as an alternative to support pollinators and biodiversity?
Patch: Instead of letting non-native plants dominate the spring landscape, try planting a diversity of native trees, shrubs and other flowering plants would better support our biodiversity. Native plants and pollinators have evolved together — the plants have traits that allow for specific interactions, the right kind of nectar and pollen (most bees are pollen specialists), and the right bloom times.
These plants are also adapted to their environments. Unlike in Europe, where most of our lawn weeds come from, April and May in eastern North America is tree and shrub season with other plants in the understory like Virginia bluebells, columbine and phlox. The flowering trees provide a bonzanza of resources for bees and other pollinators. It is not really until June that the great majority of open meadow plants — like the ones found in our lawns — begin to bloom.
Consider converting your yard into a pollinator haven, adding plants and flower beds over time until you convert your entire lawn into a garden. This garden will beautify your home, improve your well-being and enhance your neighborhood. And it will be a place where pollinators can thrive. Plant May flowers and enjoy them for the whole year!
Q: Are there other benefits to keeping lawns mowed?
Grozinger: Yes. Another reason to keep grass trimmed is to reduce the risk of tick-borne diseases. Leaving grass unmowed in May creates a favorable habitat for ticks, as well as wildlife such as rodents and deer that carry ticks. Maintaining shorter grass can help reduce tick populations around your house.
Q: Where can people learn more about supporting pollinators?
Grozinger: For more information, including lists of common non-native weeds and flowering plants for May and June, as well as resources to help you select the best plants for supporting bees, butterflies, hummingbirds and other pollinators, visit the Center for Pollinator Research website. If you want to go a step further and create a pollinator garden, look at the Penn State Master Gardener’s Pollinator Garden Certification program. Penn State Extension also has excellent resources for reducing tick exposure.