In a previous blog, we discussed the benefits of having native butterfly and moth caterpillars in the backyard. They won’t damage your trees and shrubs; instead, they are both beautiful and contribute to the ecosystem by pollinating plants and serving as food sources for birds, which helps maintain balance in their populations. In this blog, we will explore how soft landings can further enhance your yard as a welcoming habitat for butterflies, moths and other pollinating insects.
Host plants and keystone plants
If you’ve been learning how to enhance biodiversity in your yard, you've likely come across terms like “host plants” and “keystone plants”. But what exactly do these terms mean? “Host plants” are typically native to a local region and provide essential food to support insects in their larval form, such as caterpillars. “Keystone plants” are like superpowered native host plants – they are crucial for the overall health of an ecosystem, as they support a significant number of insect species.
Why are keystone plants important? According to pollinator conservationist and award-winning author Heather Holm, “planting keystone plants helps build complex food webs by forming the essential foundation —native plants and insects — that provide food for other organisms, directly and indirectly.” Just as a house needs a strong foundation, a healthy ecosystem requires the right plants as a foundation. Without these “key” plants, an ecosystem will collapse.
Keystone trees and shrubs are particularly noteworthy for the number of insect species they can support. According to entomologist Doug Tallamy, 14% of native plants support 90% of butterfly and moth species. Among these keystone species, trees play a particularly vital role, with the top 10 most important plants for butterflies and moths being trees like native oaks, cherries and birches. And with their large biomass and surface area, these trees and shrubs provide ample food and space for insects to thrive. However, relying solely on trees and shrubs in your yard has its limitations.
The limitations of relying only on trees and shrubs
The first limitation is that trees and shrubs cannot fully support all insect populations. Many insects rely on native flowering plants and grasses instead. A well-known example is monarch caterpillars, which feed exclusively on milkweed species. In fact, some native flowering plants, such as goldenrods and asters, serve as host plants for over a hundred insect species each. These plants also offer shelter for insects in dead stems and fallen leaves. By incorporating various species of trees, shrubs, flowering plants and grasses, you can support a wider range of insect species.
The other limitation of having only trees and shrubs is the empty space beneath them. Caterpillars born in the treetops don’t always stay there. They may leave their treetop homes for two reasons: fleeing danger or searching for a new home.
Caterpillars and other insects face constant danger from predators. While some species are expert camouflage artists (like the Large Maple Spanworm, which looks like a twig and the Giant Swallowtail, which looks like bird droppings), some insects practise thanatosis – feigning death to evade predators. When sensing danger, these insects simply stop, drop and roll to the ground. Once on the ground, they will lay still until danger passes. If they are hidden within dense plantings, they have a greater chance of avoiding predators.
But caterpillars don’t always leave due to threats. After spending the first stage of their life cycle eating leaves and growing bigger, many species intentionally venture away from trees or shrubs to prepare for the next stage of their life cycle among other plants, under leaf litter or even in the soil. Here, they will try to find a safe place to form a cocoon or chrysalis.
In either case, whether fleeing danger or progressing through their life cycle, caterpillars remain vulnerable to predation or injury if they cannot find suitable shelter for hiding or pupating. This vulnerability is heightened if the ground beneath a tree or shrub is covered with manicured turf grass or pavement.
Soft landings to the rescue
Soft landings offer the perfect solution to these limitations. The term “soft landing” refers to diverse native plantings beneath trees and shrubs and typically are the same width as the tree or shrub drip line (the area located directly under the outer circumference of the branches). Not only do these naturalized areas surrounding native trees and shrubs look beautiful, but they also provide critical habitat for vulnerable caterpillars and other insects.
Soft landings do more than just assist insects with food and shelter sources; they contribute to overall ecosystem health by providing multiple food sources and nesting materials for birds and mammals, building healthy soil and even sequestering more carbon. Furthermore, by reducing reliance on turf grass, homeowners can minimize the need for water, fertilizers, pesticides and mowing, thereby promoting a more sustainable and wildlife-friendly landscape.
Incorporating soft landings with host plants under our keystone trees and shrubs isn't just about creating a visually appealing landscape - it's about fostering thriving ecosystems where insects, birds and other wildlife can flourish. Understanding the importance of diverse gardens and their role in supporting different life stages of insects enables us to take meaningful steps towards creating habitat right in our own backyards.
Ready to increase your Backyard Biodiversity and attract all the beautiful butterflies, moths and other pollinating insects? Plant for less through our subsidized Backyard Tree Planting Program! Check out our Homeowners page to get started on native tree planting and our Shrubs, Garden Kits and Pawpaws page to order native shrubs, flowering plants and grasses.
Justin Lewis is the Marketing and Communications Lead at LEAF.
The #BackyardBiodiversity campaign is a partnership initiative with the Toronto Wildlife Centre and is supported by Ontario Power Generation.
LEAF offers a subsidized Backyard Tree Planting Program for private property. The program is supported by the City of Toronto, the Regional Municipality of York, the City of Markham, the Town of Newmarket, the Regional Municipality of Durham, the Town of Ajax, the Township of Brock, the Municipality of Clarington, the City of Oshawa, the City of Pickering, the Township of Scugog, the Town of Whitby and Ontario Power Generation.