Not mowing this month? Some say it's the way to go, others not sure

To mow or not to mow — that is the question, starting in May.

And a Moncton researcher hopes that for the sake of biodiversity, the answer for many homeowners will be not to mow.  

The annual "No-Mow May" initiative has gained popularity over the past several years as a way to increase the food supply for pollinators, such as bees and butterflies.

But there are critics as well. They cite concerns about weed growth, potential pest problems and lawn health. 

Gaétan Moreau, a professor of insectology at the Université de Moncton, is a No-Mow May supporter and has helped one New Brunswick city put the movement's claims to the test. Now he's written a report on what effects not mowing has on biodiversity. 

"I've been talking for a few years now about No-Mow May all over the place, and Alexandre Truchon-Savard from Dieppe called me one day … and said, 'Would you like to test No-Mow May here in Dieppe?'" Moreau said.

Truchon-Savard, the City of Dieppe's director of environment, said the idea came after a change to the municipal bylaw on lawn height. 

As of last year, he said, there is no longer a requirement that lawns on private property not exceed a certain height, as long as the grass doesn't interfere with public spaces or signage. 

To test the No-Mow May rationale, Dieppe identified some municipal areas that have always been mowed but aren't necessarily used a lot.

They picked six spots and applied three different treatments. They let one section grow, kept one section mowed and replaced one section with a mix of wildflowers.

This is where Moreau came in. He said because they would need to trap pollinators in order to count them, they instead chose to study resident organisms such as ground beetles, which live above ground, and invertebrates that were under the ground.

Testing the abundance of these organisms allowed Moreau to identify whether the area was a good habitat, which would in turn help pollinators.

Over the summer, he said, the unmowed area had a positive impact on below-ground organisms.

But the area replaced by flowers showed the biggest improvement, with beetles even moving to those areas.

For Moreau, this proved that No-Mow May can be beneficial.

"When you stop mowing, you're giving a break to this ecosystem," he said.

But not everyone is thrilled about the catchy concept of No-Mow May. For Sara Stricker of the Guelph Turfgrass Institute, the expansion of No-Mow May throughout North America was a red flag for fellow grass experts.

She would rather not pin the effort to a particular month, given how weather and other factors affect the growth of lawns.

"We don't do anything based on a calendar," she said. "We don't time our management based on what month it is."

For the last few years, she's been doing a research project based on No-Mow May, letting a plot of land grow for the month unrestricted.

Two years ago, there was heat but not much rainfall, which led to the grass growing 35 centimetres tall. The next year, there was much more rain and more heat, leading to 108-centimetre grass, along with ticks.

Eric Lyons, an associate professor of plant agriculture at the University of Guelph, said most of the species that make for good lawns require constant lawn mowing. 

"If you want to use your lawn in June and July, it's important to mow it in May, so that those species do not get weak and do not basically shade each other out, get very thin and then not be able to withstand the use that we want to use our lawns for," he said.

Lyons agreed that lawn maintenance isn't just about picking a specific month. Every lawn is different every year.

For example, he said, some New Brunswick springs have a cold and wet May, leading to almost no growth. In this case, he said, you probably won't be mowing your lawn until mid-May anyway, but flowers also likely won't bloom yet.

"It's important to pay attention to what's happening on your lawn or in your gardens to provide what you want to do with that area."

Jordan Phelps, a Bee City Canada co-ordinator based in Ontario, said No-Mow May has become quite polarizing over the years, but his position on the topic falls somewhere in the middle.

He said some concerns with No-Mow May and letting your lawn run wild include the potential spread of invasive species. 

Phelps said it's important to consider that No-Mow May originated in the United Kingdom, where a lot of plants that occur naturally on yards are native, but in North America, this isn't necessarily the case. 

He said it's also important to be thinking outside May, because a lot of pollinators emerge in April, and are really active in June. 

But he believes that having the initiative is an important way to spread awareness and encourage support for pollinators in the longer term.  

"It's kind of a way to get people in the door so that they're interested in learning more and more about pollinators,"  Phelps said. 

"They can then kind of take further action and ideally just have less grass overall and use some of that space for planting native plants."

At the Université de Moncton, Moreau hopes for the same. He wants to see people rethink the need to mow several acres week after week.

"There's a lot of simple things we can do to bring back biodiversity in your backyard, and some things that people don't think about," he said.

"For example, just keeping your cat inside. It's already a pretty big way to bring back bird biodiversity around your place. So there's little steps, and I think this is one of them: rethink this model. Do we need that much land mowed?"