To leaf them on your lawn or not: U of G expert weighs in

'Some' leaves can stay on your lawn this fall.

But if you don't like that idea, there are other alternatives to raking that might be better for your lawn and for the environment.

University of Guelph turfgrass researcher Sara Stricker believes it depends on the many different types of leaves, but a happy compromise is always possible.

"It really depends. How much leaves? What kind of leaves? Is it a black locust, which has tiny little leaves, or is it a Norway maple that has leaves bigger than the palm of your hand? This can all make a big difference," Stricker said.

"If I were to leave my Norway maple leaves on my lawn, they would kill it and then I would have a mud puddle."

Stricker, communications and outreach coordinator for the Guelph Turfgrass Institute (GTI), said acidity in specific types of leaves can also have an impact on lawns when they break down.

An area of turf at the GTI that had been covered by leaves for a experiment.

"Leaving leaves on the grass can actually damage lawns, since grass is unable to 'breathe' underneath," she said.

“Smothering and turf death can occur, especially if you cannot see any turf blades sticking through."

Stricker said anything longer than three weeks of tree leaf coverage could damage or kill turfgrass, depending on how deep the leaf coverage is.

However, leaving 'some' leaves on your lawn is ok.

"Any living organism, needs oxygen, or they will die. So, imagine, if you are under water and you need a snorkel. The blade of grass, sticking up between your tree leaves, is the snorkel," she said.

"If you want to leave the leaves on the grass as a natural fertilizer, running your mower on it, multiple times, will help."

Properly mulched tree leaves can act as a natural fertilizer.

"They do make a great fertilizer, especially, here in Guelph, where we don't do leave pick-up. This is a very good option," Stricker said.

Other alternatives to help pollinators thrive, include composting leaves or building a leaf tower out of chicken wire.

"This is one of the greatest ways you can leave your leaves in your yard and create a biodiversity niche. You can make either a circle or square out of chicken wire. It's like an open container, and you can fill your leaves into that. I actually have one and it also helps compost," Stricker said.

"It's a great way to get some good quality soil. I can fit most of my leaves in my leaf tower which only takes up about a metre squared in my backyard."

Stricker said using leaves as you would wood mulch can help to create a pollinator refuge, a great organic fertilizer for your lawn or garden and a natural weed suppressant.

As for removing leaves, shes says raking is usually recommended over a leaf blower, since it can help remove thatch and introduce air into the system.

"Raking is better but leaf blowers are useful especially if you have really small leaves. They are a pain to rake. So, the leaf blower can help especially when cleaning up edges. It can also help with accessibility, because some people can not manage a rake which is more physically exhausting," she said.

Stricker says leaving leaf matter on the ground can benefit pollinators and increase biodiversity by creating homes for insects and other wildlife. 

“Create a habitat in an area of your yard with low traffic,” she said. “This can include wooden logs, hollow flower stems, leaves and stones. This biodiversity refuge would be most beneficial if left undisturbed year-round to allow for nesting and breeding as well.”

"You can still have these excellent biodiversity niches and then also still have a functional lawn next spring."