Do my favourite garden plants have an ecological purpose?

Bird on goldenrod — Golden-crowned kinglet feasting on goldenrod seeds, Toronto ON. © Jack Breakfast

We love our gardens. We love to personalize our outdoor spaces with artistic originality, with plants from our grandmothers, sisters, friends…plants we’ve loved since childhood. But do these beloved friends have an ecological purpose? We’re finding out that some do, but some are harmful, and some are just not very helpful.

Monarch feeding on Liatris. © Andrea Brennan

Let’s start with Doug Tallamy’s explanation of ecological purpose: it all starts with native plants, which support native insects, which in turn support a wide array of other wildlife. All living organisms are interconnected in ecosystems, meaning that every species plays a vital role in maintaining ecological balance.

What does this have to do with my home landscaping?

Unfortunately, the way we’ve been landscaping our properties for the past few hundred years (conventional landscaping) hasn’t been supporting native plants and insects - in fact, it’s been suppressing them, through the import of plant species from different countries and continents, creation of large swaths of lawns, heavy use of fertilizers and excessive water usage.

Let’s look a bit deeper into the issues with conventional landscaping.

Non-native plants: Conventional landscaping often relies on non-native plants, many of which don’t do a very good job of supporting local insect populations. This leads to a decline in biodiversity, as native insects and other wildlife struggle to find suitable food and habitat. Think of a non-native plant as a statue - it looks nice, adds an interesting element to the landscape, but does it have an ecological purpose?

Non-native plant garden — A pretty garden, but an ecological desert. © Andrea Brennan

Is it providing food and shelter for our local insect population? Is it a host plant for one of the caterpillar species that our local bird population needs to feed their young? Douglas Tallamy and Kimberley Shropshire’s research (2009) found that native plants support fifteen times more species of Lepidoptera (butterflies and moths) than ornamental, non-native plants!

Swallowtail butterfly on zizia — Black swallowtail feeding on its host plant, *Zizia aurea,* New York. © Janet Allen

Some non-native plants are very aggressive and are considered invasive species. These plants disrupt natural areas and suppress the native plants that host our important insects and wildlife. The Ontario Invasive Plant Council has published a very handy resource called Grow Me Instead, which has some great suggestions of native plants you can use to replace the invasive plants in your garden.

Goutweed spreading in forest — *Aegopodium podagraria* (goutweed) spreading in the forest. © Viktoria Wagner

Habitat Fragmentation: When we design landscapes with only the homeowner in mind, we are overlooking all of the wildlife that already call this space home. Have you ever walked through a neighbourhood and noticed how different each home’s landscape can be? True, this is an important way to express our individuality, but there are certain elements that need to be included in order to ensure that the ecological habitat remains connected. If each neighbour incorporated native plants to their yards and gardens, fragmented habitats would be reconnected - our local insects and birds would expend less energy searching for suitable food and shelter.

Warbler on asters — Yellow-rumped warbler on goldenrod and asters, backyard in Toronto, ON. © Jack Breakfast

If you replace your non-native daylilies (Hemerocallis spp.) with native goldenrods and asters, you’ll be providing habitat for many birds and insects, including the migrating warblers. Imagine if everyone on your street planted goldenrods and asters!

Resource Intensive: You love your hybrid-tea rose (Rosa x hybrida), but it requires a lot of extra inputs in order for it to be at its best - it needs lots of water, regular fertilization, pruning and dead-heading, fungicides and insecticides to combat pests and diseases, and it needs to be wrapped for protection from harsh winter conditions. When many of us are caring for plants in this way, we are contributing to water scarcity, energy consumption, greenhouse gas emissions and plastic pollution.

Does your garden plant require extra inputs to help it survive, or is it well suited for the type of soil and amount of sun in your yard? Native plants that are selected for the ecosystem your home dwells in will require minimal inputs and waste and will thrive when planted in the right place. Often deep-rooted, these plants will also restore water and stabilize soil, while enhancing ecosystem resilience.

Veronicastrum supporting wildlife in a garden, QC.

These are just a few examples of why some of our favourite plants might not be the best to keep in our landscapes anymore.

What should we do?

Let’s add some native plants to the land!

Have a good look at your landscape this spring and ask yourself if each plant is helpful or harmful - does it have an ecological purpose? Check out some local native plant resources, and see how many “statues” you can replace with ecological powerhouses! Consider filling empty spots in your garden with native plants that will invite insects and birds to forage.

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Resources:

How to find which plants are native to your area:

Pollinator Partnership Canada: Enter your postal code for a list of native plants for your region!
Canadian Wildlife Federation: Native plant suppliers list
Ontario Invasive Plant Council: Grow Me Instead