Fall has arrived once again, heralded by the annual dance of red, yellow and orange leaves. For many, this means it is time to bring out the rake and tidy the garden before winter. This practice has long been a norm of gardening, even among many that intentionally garden to attract pollinators during the spring and summer months. While raking the leaves, cutting the seed heads or stems from flowering plants, and bagging them for pick-up may feel like the right thing to do, these practices are disruptive to the very native pollinator populations that many of us are trying to support.
While some pollinator species, such as the well-known monarch butterfly, migrate to avoid the cold, the vast majority of native pollinator species overwinter close to home. Indeed, many native pollinator species overwinter beneath and within plant material, such as beneath dead leaves and other plant cover, and within dead stems. Many butterfly and moth species, for example, overwinter within or beneath leaf cover, either as eggs, caterpillars, pupae, or adults. Bumblebee queens – including the vulnerable Yellow-banded bumblebee – often overwinter underground, with leaves providing a much-needed layer of additional insulation. Solitary bees, which can be quite tiny, are even known to overwinter inside of dead plant stems. Thinking beyond overwintering pollinators, many animals benefit from leaves and other plant material being left, including birds, mammals, amphibians, reptiles, and other insects. The soil also benefits greatly from left plant material; as plant material decomposes, it provides much-needed nutrients back to the soil, which supports the plants that will grow back in spring, and in turn the animals that will feed on those plants.
Leaving the leaves, stems, and other plant material may seem obvious in natural areas, where this has occurred for millions of years. As Aristotle wrote, “nature does nothing uselessly.” Animals have evolved over time alongside the pattern of falling leaves and now depend on leaves in a multitude of ways. This perspective is important to consider as we try to support wildlife in our own yards. With the single goal of supporting wildlife in our yards, we would cultivate a diverse community of native plants and leave the plant material untouched to provide value to animals and to the soil as mulch. For many of us, however, supporting wildlife is an important goal, but not the only goal; in addition to habitat areas, many of us also enjoy maintaining turfgrass to support pets and activities. While a thin layer of leaves can benefit turfgrass, a thick layer can be detrimental.
While overall we recommend replacing as much turfgrass as possible with native plants, and leaving them untouched during the fall months, we recognize that many people will continue to maintain some turfgrass. Regardless of how much turfgrass you maintain, you can make a meaningful difference for pollinators and other animals by leaving as much plant material as possible. Here are our recommendations for if you would like to join the ‘leave the leaves’ movement this fall:
- If your yard is entirely turfgrass, and a thin layer of leaves has fallen, consider leaving the leaves as they are. A thin layer of leaves will not damage the grass.
- If your yard is entirely turfgrass, and a thick layer of leaves has fallen, consider spreading them out, or moving them elsewhere, rather than bagging them up. Doing so will support overwintering pollinators.
- If you have some turfgrass and some native garden area, and a thick layer of leaves has fallen, consider moving the leaves from the turfgrass into the garden area. A thick layer of leaves will provide valuable mulch and benefit the garden as it grows back next year.
- If your yard contains no turfgrass, consider leaving the leaves and other plant material untouched to best support the soil and overwintering pollinators.
- Watch out for diseased leaves, and remove any that you find, as these can have negative impacts on plants the following year.
- Even if committed to leaving the leaves, remember to clear leaves from sidewalks to prevent people from slipping on them. Consider moving any leaves from the sidewalk into your garden.
- Remember to leave the leaves and other plant material well into the spring, when temperatures are consistently above 10℃, to ensure that overwintering pollinators have had a chance to emerge first.
- Share the importance of leaving the leaves with your friends and family, so that everyone understands the importance of this action for pollinators and ecosystems.
Many Bee Cities and communities across Canada have taken steps to encourage residents to leave the leaves and other plant material to support overwintering pollinators. We encourage you, whether as a municipality, a campus, a school, or an individual, to leave the leaves and other plant material to support pollinators this season, at a time where every small gesture counts!