Ottawa gardeners weighing whether to rake up this fall have a good reason to leave the leaves where they land, according to Barbara Sibbald, a volunteer with Master Gardeners of Ottawa-Carleton.
Why leaves matter for wildlife
A 2025 study by Max Ferlauto and associates found that removing leaves reduces butterfly and moth species abundance in spring by 45 per cent, beetles by 24 per cent, and spiders by up to 67 per cent. That's a steep cost for a tidy-looking lawn, since many of these insects overwinter in leaf litter and emerge in spring to pollinate gardens and feed birds.
Leaves feed the soil
Beyond sheltering insects, decomposing leaves return 50 to 80 per cent of the nutrients they contain back into the soil, acting as a free, slow-release fertilizer for garden beds. A layer of leaves also reduces surface water runoff by about 30 per cent and cuts soil erosion by up to 85 per cent, which matters in a city like Ottawa where fall rain and spring melt can otherwise wash topsoil off sloped yards and boulevards.
How much lawn should stay covered
For Ottawa homeowners worried about their grass, turf experts say it may be okay to leave 10 to 20 per cent of a lawn with a thin covering of leaves, but no more than that. Beyond that threshold, a thick mat of wet leaves can smother turf over the winter, so a light scattering rather than a full blanket is the balance to aim for on lawn areas.
When it's safe to tidy up in spring
The advice isn't to never clean up, just to wait for the right moment. Gardeners are advised to hold off on spring tidying until nighttime temperatures are consistently 10 C, since clearing beds too early disturbs insects that are still emerging from the leaf litter and plant stems where they overwintered.
Chop and drop for perennial stalks
For gardeners who do want to cut back perennials in fall or spring, Sibbald recommends a practice called "chop and drop": chopping the cut stalks into 20 to 50-centimetre chunks and dropping them by the plant's roots, where they decompose and return nutrients to the soil rather than heading to the curb.
For Ottawa gardeners who spend the fall raking out of habit, the message from the region's Master Gardeners is simple: a messier-looking yard through winter is doing more work for pollinators, soil health and stormwater than a bare, raked one ever could.
Sources: Ottawa Citizen (via Yahoo News Canada)
