Yay or Nay to #NoMowMay?
The campaign was designed to feed pollinators, but long grass causes more problems! We dive into where it originated, what makes sense, and recommendations based on science.
The fresh growth of spring means the return of the #NoMowMay campaign encouraging homeowners to let their grass grow longer to help insect pollinators. As the experts in grasses, we’ve been asked by the public and media to weigh in with our opinion.
Is No Mow May a bad idea?
We feel that this a great campaign for starting a conversation about supporting our pollinators. However, it is a little misguided. Many early-flowering weeds that can be found in lawns, such as dandelions, are actually an incomplete source of nutrition for pollinators.
“Dandelions aren’t going to save the bees,” says Dr. Eric Lyons, associate professor at the University of Guelph. “A much better nutrition source for them are flowering trees, like crabapple, choke cherry and even maple, oak and willow.”
This is echoed by the Nature Conservancy of Canada in a news release in 2022.
“We are suggesting they use native plants – trees and flowers – in their yards to have a lasting impact. Many plants bloom before dandelions and are more nutritious.”
-Andrew Holland, NCC national media relations director
What’s more, creating temporary habitats in the form of an overly long lawn is not helpful to pollinators if the plan is to eventually mow the grass into a lawn. Plant pollinator-friendly flowers, grasses and shrubs instead. If you feel very motivated to support pollinators, you could create wildflower zones in home gardens with pollinator-friendly grasses and shrubs to benefit insects and wildlife all year round. Note that these areas can attract all kinds of biodiversity, even some of the pests that we don’t like (fleas, ticks, mosquitos) so we recommend putting these “Naturalized Zones” in an area away from children and pets.
From a turfgrass perspective, “No Mow May” can harm the home lawn.
“Allowing lawns to grow long can encourage the growth of undesirable weed species such as thistles, prostrate knotweed and wild violet, which are difficult to remove once they become established. It will likely take more inputs of water, fertilizer, seed, and herbicides to get your lawn back into shape after a #NoMowMay.”
-Dr. Sara Stricker, Guelp Turfgrass Institute Communications and Outreach Coordinator
Cutting too much of a grass’s length at once is also traumatic, leaving the grass with a sudden loss of an energy source during an active growing time. Tall grass is also difficult to mow, which can increase the risk of “scalping” the turf, making the lawn more susceptible to insects, weeds and disease.
“We recommend mowing home lawns when the grass reaches approximately three inches high,” said Lyons. “Grasses have evolved to be grazed upon by herbivores, so they actually respond positively to mowing practices.”
-Dr. Eric Lyons, Professor at the University of Guelph
The #NoMowMay campaign has gone viral because of its simplicity. Do nothing = support environment. Unfortunately, conservation efforts are rarely so simple. Talk to your local garden centre about which plants are best for your region, and which are native in your Hardiness Zone. In general, planting perennials is recommended since they will come back every year (easier for you to maintain) and it reduces on shipping/manufacturing inputs.
#MowWhenYouGrassNeedsMowing doesn’t have the same ring to it, but perhaps we can promote #PlantNatives instead?
However you decide to manage your property, take into account the function of the space. If you want a garden of flowers, then you can create that. If you want a functional space for events, play, or exercise, grasses are the most resistant to wear-and-tear and foot traffic.
Infographic Posters
Download this handy poster on #Know2MowMay to print or share electronically.
Pollinator assemblages on dandelions and white clover in urban and suburban lawns
by Larson et al., 2014, Kentucky USA
- 50 different pollinator species visited dandelions and clover mowed at 6.4–8.9 cm (2.5–3.5″) every 7 to 10 days
- White clover attracted Western honeybee (Apis mellifera), dandelion attracted syrphid flies (Syrphidae)
- Species richness of bees on white clover was similar in urban, suburban, and periurban-rural lawns
- Syrphidae tend to favor open, shallow flowers (like dandelion) whose nectar and pollen are accessible to the flies’ relatively short mouthparts
- Long-tongued bees tend to avoid shallow flowers that offer only a small amount of nectar per flower, preferring plants that offer more energetically-advantageous floral rewards like clover
- White clover is better suited than dandelion for bee conservation lawns
To mow or to mow less: Lawn mowing frequency affects bee abundance and diversity.
by Lerman et al., 2018, Massachusetts US
- Lawns mowed every three weeks had as much as 2.5 times more lawn flowers compared to mowing every week, or every other week
- Lawns mowed every two weeks supported the highest bee abundance
- Mowing less frequently is practical, economical, and a timesaving alternative to lawn replacement or even planting pollinator gardens
- Grass in this study was cut to 6.35 cm. The height of the grass in each mowing frequency was approximately 11.2 cm (1 week), 12.5 cm (2 week), and 15.cm (3 week)
Lawn mowing frequency and its effects on biogenic and anthropogenic carbon dioxide emissions
by Lerman & Contosta, 2019, Massachusetts USA
- In lawns, carbon dioxide is emitted by soil respiration due to microbial activity and by fossil fuel burning.
- Mowing frequency (7 days, 12–14 days or 18–21 days) did not consistently change soil moisture, temperature, and soil respiration.
- Carbon dioxide emissions from soil microbes were: 482 g/m² s ( weekly), 436 g /m² (every other week), 458 g/m² (3 week) – no significant differences between treatments,
- Carbon dioxide emissions from mowing by frequency were: 16.3 g/m² s( weekly), 10.7 g /m² (every other week), 6.9 g/m² (3 week)
- Although mowing time might be shorter when using a rider mower, rider mowers emit more than four times as much CO2 compared to a push mower
- Increasing tree canopy cover in lawn-dominated yards and replacing some lawn with other vegetation that requires less intensive maintenance can reduce carbon dioxide emissions
From urban lawns to urban meadow: Reduction of mowing frequency increases plant taxonomic, functional and phylogenetic diversity
by Chollet et al., 2018, France
Important note: this study applies to grasslands 5–10 ha in size (50,00- 100,000 m², 12–24 acres)
- Mowing frequency is 15 –20 times per year in highly managed grasslands, 7–9 time per year in intermediate, and once per year in low managed grasslands.
- The low mowing frequency presents a higher plant diversity compared to the high mowing frequency grasslands
- The intermediate mowing frequency failed to produce any increase in plant diversity
- Frequent mowing selects for disturbance-tolerant pioneer species and grasses
Local garderning practices shape urban lawn floristic communities
by Bertoncini et al., 2012, France
- The location of the lawn in a public green space, foot traffic, frequent mowing, and use of pesticides reduced ecological biodiversity
- Persian speedwell (Veronica persica), heal-all (Prunella vulgaris), English daisy (Bellis perennis) are a mowing tolerant flowering plants commonly found in lawns
- Location and use altered the type of weeds in the lawn: Large lawns that are distant from the urban centre favoured the establishment of perennial species that are pollinated and dispersed by wind. Frequently mown lawns mostly hosted species that are tolerant to mowing and trampling and able to reproduce sexually and asexually. Small, rarely mowed lawns, situated near the urban centre supported communities of annual species that are self-pollinated and intolerant to mowing and trampling.
- Green areas are important for people living in urban areas, so it is necessary to find practices that can reconcile the presence of the public use and biodiversity management.
Partial mowing of urban lawns supports higher abundances and diversities of insects
by Wintergerst et al., 2021, Germany
The size of lawns/meadows in this study ranges from 815 m (0.2 acre) to 3460 m (0.9 acre), mowed 0-5 times per year.
- Some mowing (1-3 times/year) is required in order to prevent a meadow from becoming fallow ground.
- The reduction of mowing frequency extends the time window during which plants and insects can develop, leading to higher biodiversity.
- Every time an area is mowed, a part should be left uncut (about 30%). The uncut area rotates with every mowing event in order to prevent fallow.
- Tall grass areas or meadows are essential for insect overwintering
To mow or not to mow in May
No Mow May? Yeah, maybe not, says University of Guelph expert
Sara Stricker, communications and outreach co-ordinator for the Guelph Turfgrass Institute at the University of Guelph, has been reaching out to media outlets in recent weeks advocating against people letting their lawns grow long during the month of May for pollinators
No Mow May – Does it Work?
by Garden Fundamentals, Robert Pavlis, Ontario
- #NoMowMay began along roadsides in the United Kingdom – very different than lawns in North America
- Lawns that have been treated with herbicides will not create flowers for pollinators
- In Ontario, the most abundant pollen source is native trees
- Extremely high grass actually has fewer flowers
- Cutting high grass can stress out the lawn
- There’s no long-term benefit to #NoMowMay
No Mow May Results and Feedback
by Liz Zorab, Byther Farm, UK
- Think about your “exit strategy”: how to cut long grass and dealing with weeds that are setting seed.
- If you are expecting to return your lawn to “bowling green beauty”, you’re going to be sorely dissappointed. Think carefully about what you really want your lawn to be.
- If you want a functional lawn, have a mowed area.
- If you have a very small yard/garden, then #NoMowMay doesn’t make sense. Add flowers to your borders rather than allowing your lawn to grow long – after all, children need an area to play
- We are cutting most of it, and letting the corners and the edges grow long to allow for wildflowers.
- Manage weeds (like docks) to prevent them from going to seed
- Give #NoMowMay a try, but be prepared to adapt and change your practices in the future
‘No Mow May’ not all it’s cracked up to be, says Peterborough gardening expert
by Global News, Ontario
- We have a lot of growth in May, and I can’t imagine how difficult it would be to get my grass back into a “lawn state” in June
- Dandelions are a food source for some pollinators, but they are not native and they are not a great food source
- Better food sources for pollinators include trees, hyacinths, crocus, and daffodils. Most of those pollen sources live in gardens in wild areas, not lawns
- 350,000 varieties of pollinators exist, so we should plant native species that they are looking for
- Adding clover to a lawn can provide pollen, and can be an alternative to grassy lawns if you have a white grub infestation
Is the science behind an initiative to naturally grow your lawn flawed?
by Dr. Torah Katchur, CBC Radio One, Edmonton and Guelph Turfgrass Institute, Ontario
- Trying to apply a campaign (designed in UK) across all of Canada does not make sense
- Cutting a grass down after #NoMowMay can result in scalping, thus damaging the lawn
- Leave some leaves in your back yard (in corners and under trees) to allow pollinators to overwinter – rake leaves off the lawn so you don’t smother the grass – but allow pollinators to overwinter until the threat of frost has passed
- Mulch leaves over the lawn – it acts as fertilizer
- Plant a strip of wildflowers, or add crocus/snowdrop into your lawn
- Turn lights off at night to support moths
- Avoid pesticide use to support beneficial insects
- Creating naturalized prairies/meadows is recommended in rural areas
Why grass experts say No Mow May might be a bad idea for local lawns
by CTV Kitchener and Guelph Turfgrass Institute, Ontario
- Self-shading can occur when grass grows too tall
- The Nature Conservancy of Canada agrees that dandelions are not a great source of pollen
- #NoMowMay increases the risk for weeds and makes it harder to maintain the lawn for the rest of the year
- Plant flowers to support pollinators. Clover can be added to a lawn and mowed.
- Months that are hot and dry (like July) are when mowing is not needed
New research has scientists re-thinking the popular No Mow May Idea
by KARE 11 with University of Minnesota’s Turfgrass Extension Educator, John Trappe, USA
- Research from Wisconsin initailly supported the #NoMayMay movement, but has since been retracted
- We don’t know for sure if there are positive effects on pollinators, but we do know that there will be some negative impacts on our lawn.
- Grass grows excessively during the spring, and the clippings from mowing in May provide nutition and water-holding capacity to survive drought in the summer.
- Mowing in June will create excess clippings, these will liekly be bagged and removed from the lawn – a practice that is not recommended
- Mowing tall grass can create an extreme volume of clippings, which could smother the turf
- Create a “bee lawn” – yarrow and self-heal can be seeded into lawns (in Wisconsin) as food for pollinators that can also be mown
The PROBLEM with No Mow May
by Naturally JB, UK
- The advertisements for #NoMowMay show amazing meadows bursting with colour and wildflowers, but that is an unrealistic expectation for a typical home lawn
- People try it, end up with tall grass, and have a tough time mowing it back into a lawn afterwards
- If you really want to create nectar resources for pollinators, it takes time.
- There is biodiversity in a lawn if you alter your expectations and allow plants typically thought of as weeds to establish
- Create structural diversity in your yard – shorter grass, taller grass, and flowers.
- Wildflowers are not accustomed to fertilized lawn areas – recommendations for changing the lawn to a wildflower garden are provided.
Bee Lawns and Slow Mow Summer
by Angie Hong, East Metro Water, Minnesota USA
- The best action to support pollinators and other wildlife is to plant native trees, shrubs and flowering plants
- Replacing some turf with native plants also helps to create pockets of habitat, improve soil health, and reduce environmental impacts from mowing, watering, pesticides and fertilizers.
- #NoMowMay is the ecological equivalent of opening a fast-food restaurant on every corner – for a short amount of time.
- People can provide better forage for native bees by enhancing their existing lawns with flowering species
No Dandelions in Long Grass
TikTok by Angie Hong, East Metro Water, Minnesota USA
- Several dandelion flowers are seen in the mowed section of a roadside.
- In the tall grass, no dandelions are seen.
- Dandelions grow best in lawns, disturbed areas, or along trails
Mow your lawn or not? That’s the debate for May
by Leah Gerber, The Observer Newspaper, Elmira Ontario
- We’ve seen a really warm spring, so the grass is growing and it needs to be mowed
- Our grass is designed to be mowed and it’s healthiest when it’s mowed regularly.
- Lawns have a purpose in urban settings
- A better option than not mowing, she says, is to set aside a portion of the property to be solely dedicated to being naturalized and left for pollinators.
- Not mowing in the month of May or reducing the frequency of mowing is better for pollinators than doing nothing
- Flowers considered to be weeds that first come up, like dandelions, do not have as much pollen, their abundance makes up for that
- Leaving leaf piles and hollow stems over winter creates nesting sites for cavity-nesting bees
Season 4, Episode 12 (lawn and landscape): No Mow May - Yay or Nay?
by Dr. Frank Rossi at Cornell University
- Lawns can offer ecosystem services to pollinators, but we need to think differently about them.
- Minnesota offers rebates in your incorporate flowering species into your lawn – but a more diverse ecosystem means you might need to change your management practices.
- Reducing mowing frequency will reduce fossil fuel use. For example, the “Tall Grass less Gas” project.
- Increasing mowing height can allow for flowering plants with prostrate and creeping growth habits to survive in lawns.
- Snakes might inhabit long grass.
What is the optimal mowing height and frequency for lawn-height turfgrass?
by Glen Obear, D.J. Michael, Bill Kreuser, Ph.D. at the Department of Agronomy and Horticulture, University of Nebraska-Lincoln
Note: This was conducted on irrigated tall fescue stand.
- Mowing to the 1/3rd Rule (33% mowing threshold) resulted in acceptable lawn quality with no scalping and fewest mowings compared to other treatments.
- Mowing to the 50% threshold caused some scalping, but can be an option for lower maintenance lawns.
No Mow May, Low Mow Spring
by Bee City USA
- Re-thinking the American lawn can take a variety of forms from reducing mowing frequency or area mown to permanently converting lawn to a more diverse and natural landscape.
- Floral resources may be hard to find, especially in urban and suburban landscapes. By allowing it to grow longer, and letting flowers bloom, your lawn can provide nectar and pollen to help your bee neighbors thrive.
- You don’t need to go a full month without mowing. Mowing every two or three weeks can increase flower blooms and provide food for hungry bees.
I am participating in No Mow May
by Blue Marble Learning Scene
- If you want grass to grow in your yard then no mow May is not going to help. If you consider “weeds” to be bad then again, no mow May is not for you.
- When (lawns are) left to grow throughout May, flowering plants have a chance to flower. Regardless if the flowers in your yard are complete food sources or not, any food is better than nothing for our pollinators.
- Pollinator gardens and more flowering / fruiting trees are better, but as we work towards this, no mow May will help.
- The choice to participate or not is up to each of you and we hope that everyone can move forward respecting individual decisions on this topic.
No Mow May? Good intentions, bad approach, critics say
by Jessica Damiano, AP News
- Some of those pollinators you set out to protect will likely get shredded up with the first mow of the season
- Weeds and invasive plants that take hold during the month won’t simply disappear once the mowing commences. That might lead people to apply chemical pesticides they wouldn’t otherwise use.
- “It’s such a nice slogan, but letting the grass grow high and allowing it to do its thing, and then suddenly mowing it back is really counterproductive” says Tamson Yeh, turf specialist with the Cornell Cooperative Extension of Suffolk County.
- Yeh cautions that “allowing grass to go to seed will kill it,” so remove seedheads if they form.
No-Mow May: feel-good movement or selfless sacrifice for pollinators?
by Hannah Rudderham, CBC News, New Brunswick
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Sara Stricker, a turf researcher at the University of Guelph, says leaving the lawn to grow might not be the best course of action for these species.
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“It’s a catchy hashtag … You make cute banners, you know, ‘pardon the weeds and feeding the bees’ or something like that. It’s a feel-good movement,” Stricker said.
- Andrew Holland with the Nature Conservancy of Canada, based in Fredericton, agrees. He said dandelions are not that nutritious for pollinators and they prefer native plants and shrubs as a food source
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Stricker said people shouldn’t judge their neighbours for wanting to mow their lawns. Similarly, Holland said people also shouldn’t judge those who don’t have short, trimmed and “pristine” lawns.
The surprising downside of #NoMowMay
by Sheila Colla, Rewilding Magazine, Canada
- Not cutting your lawn and letting dandelions grow for a month is touted as an easy way to help bees. But one-size-fits-all solutions don’t work for conservation.
- A month of long lawns filled with dandelions and other non-native weedy species doesn’t create biodiversity and ecological integrity.
- Manicured, monocultural lawns are pollinator deserts – the less lawn the better. Replace part of your lawn with densely planted native plants if pollinator support is your main goal.
What’s the deal with “No Mow May?”
by Hannah Gaines Day, Claudio Gratton, Julie Hill, Paul Koch, Kristin Krokowski, PJ Liesch, Madisen Potratz, Mark Renz, Tim Ripp, Doug Soldat at University of Wisconsin-Madison, USA
- Lawns that are mowed higher (more than 3”) and less often tend to have more flowering plants, supporting a greater diversity of pollinators and other insects
- Low-growing flowering plants like Dutch White Clover (Trifolium repens), Self-heal (Prunella vulgaris) and Creeping Thyme (Thymus serpyllum) will add diversity to the flowering plants in your yard and can tolerate mowing and some foot traffic.
- If you are worried about being stung, plant away from high traffic/play areas.
- Delay your spring clean-up and/or tilling of these places until late spring (late May) after pollinators have emerged as adults from their overwintering nests.
- Learn more about how to provide shelter and nesting habitat for pollinators: Xerces Society’s Nesting and Overwintering Habitat publication.
No Mow May: A Gateway to Better Landscape Management for Bees
by Matthew Shepherd and Laura Rost, Xerces Society for Invertebrate Conservation
- The benefits from not mowing for a few weeks are limited.
- Letting dandelions and other weeds bloom is not good quality habitat—and any benefits will be canceled if you mow it all in June.
- People want a place where they can throw a ball, their dog can run around, they can sit with friends on a summer evening. All of those things can be done with a flower-filled lawn; you may just have to raise the cutting height and mow less frequently.
- There is no one-size-fits-all approach to No Mow May and it must be adapted to local conditions—weather, vegetation, and people.
No Mow May
by Credit Valley Conservation, Ontario
- Add diversity and a splash of colour by allowing low-growing plants like wild strawberry, strict blue-eyed-grass and common silverweed to spread throughout your lawn.
- Extend garden beds or create new ones.
- If your lawn doesn’t have heavy foot traffic, you can create a beautiful tapestry lawn of different colours and textures by planting masses of native ground covers, like Pennsylvania sedge, common blue violet and wild ginger.
Just Say No to No Mow May
by Monarch Gardens
- Just letting your lawn go will not result in a lovely meadow that neighbors or wildlife will admire
- What happens when you let your lawn go or stop mowing?
- It’s going to look weedy fast.
- Invasive species may establish.
- Woody plants will move in. Without constant management tree seedlings will start to grow.
- It’s better to design the space, to choose the plant communities that will work together AND support wildlife.
No Mow May
by the University of Minnesota Bee Lab
- Early spring blooming native plants like violets and pussy toes can be a part of your bee lawn
- For blooms in your lawns after May, add self-heal, ground plum, lanceleaf tickweed, or calico American aster.
- Leaving your leaves where they are until temperatures are above 50 degrees F (10 °C)for 5 consecutive days will give most of those hibernating pollinators the protection that they need.
- If you have an out of the way corner in your yard where you can make a pile of thatch, that could make great habitat for some bees.
- Rusty patched bumblebees are underground and are not affected by mowing, even when their nests are active.
- For some species like white clover, you may need to mow in May to encourage them to flower again if the flowers are going to seed.
No Mow May: Is it a good idea?
by the Garden Professors: Abiya Saeed, Extension Horticulture Specialist at Montana State University
- Although the intention behind this campaign is a good one, providing food for pollinators, there are some aspects of this initiative that seem to miss the mark.
- Bees and other pollinators will forage on dandelions especially if other floral resources are unavailable at that time.
- If left unmown: your turfgrass will soon outgrow any other flowering lawn weeds which can make them difficult to find for pollinators, and that is if these flowering lawn weeds aren’t smothered by the tall grass altogether.
- In many places, lawns can grow a foot or more during the month of May. An un-mown lawn can set you back on your lawn maintenance and result in more work for you in the long run.
- If you have flowering lawn weeds and pollinator conservation is your intention, your best bet would be to aim for a sweet spot between the extremes of mowing way too frequently and not mowing at all.
Neighbors Fight Over No Mow May: ‘What in the World Is Happening in This Place?’
by James Hagerty, Wall Street Journal
Sarah!
Great Website. I just found it today and want to collaborate!
We need more fact based lawn and sport turf campaigns!