The Importance of Keystone Native Plants

When we talk about native plants, it’s easy to imagine a long list where every species plays a similar role, but in reality, some native plants are far more beneficial than others. These are known as keystone species, and their presence can shape the entire health and stability of an ecosystem. Without them, many other species that rely on them for food, shelter, or nesting may disappear.

What Makes a Plant a Keystone Species?

A keystone plant species supports a disproportionate number of other species. This often means they host large numbers of caterpillars, produce critical seeds or nuts, or offer shelter to countless insects, birds, and mammals. For example, in many regions of North America, native oaks support hundreds of species of moth and butterfly larvae, which is more than any other tree genus. Those larvae then feed baby birds, which in turn feed larger predators. Remove the oaks, and that entire food web weakens.

Keystone plants are native plants critical to the food web and are necessary for many wildlife species to complete their life cycle. Without keystone plants in the landscape, butterflies, native bees, and birds will not thrive. 96% of our terrestrial birds rely on insects supported by keystone plants.

Keystone Native Plant Species of Vancouver Island

• Garry Oak (Quercus garryana)

  • Supports over 400 species of caterpillar, which feed birds and other wildlife.

  • Provides acorns as food for a multitude of mammals and birds.

  • Creates habitat for diverse understory plants.
    

• Bigleaf Maple (Acer macrophyllum)

  • Supports early-season pollinators with abundant spring flowers.

  • Leaves host over 200 species of caterpillars.

  • Decaying leaves enrich soil and support fungi and invertebrates
    

• Willows (Salix spp.)

  • Crucial early-season nectar for pollinators emerging in spring.

  • The exclusive larval host plant for many butterflies and moths.

  • Stabilizes soils and prevents erosion around riparian areas.
    

• Goldenrod (Solidago lepida)

  • Food for pollinators up until the first frosts, helping insects store energy for winter.

  • Nectar source for native bees, butterflies, beetles, wasps and other pollinators.

  • Seed heads feed birds into the fall and winter seasons.
    

• Douglas Aster (Symphyotrichum subspicatum)

  • Late-season nectar source for bees, butterflies, and other pollinators.

  • Supports a wide range of beneficial native pollinators and insects.

  • Ranked among the top perennials for supporting moths and butterflies.

    
    

• Gumweed (Grindelia spp.)

  • Critical nectar and pollen support over 30 species of bees, butterflies, and wasps.

  • Thrives in salty coastal areas and in drought conditions, making it extremely climate resilient.

  • Seeds provide food for small birds in fall and winter.

    
    

Native Goldenrod and Aster blooming in late summer (Source: facebook.com/thepollinatorpathway)

Understanding Your Ecoregion and Finding Keystone Plant Species

Before you can choose a keystone native plant for your garden, it helps to understand your bioregion, also known as an ecoregion, which is the ecological “neighbourhood” you live in. A bioregion isn’t defined by political borders but by natural boundaries like watersheds, climate patterns, soil types, and the plants and animals that have evolved there. Knowing your bioregion gives you a clear picture of which plants have co-evolved with your local wildlife and are truly adapted to your conditions.

How to Identify Keystone Species in Your Ecoregion:

Start by identifying your ecoregion with the National Wildlife Federation's Bioregion Map, which can also be seen below. Then check out their bioregional plant lists that highlight keystone native plant species. Click here for the list for the Marine West Coast Forest ecoregion. You can also use the National Wildlife Federation’s Native Plant Finder which uses your postal or zip code to rank plants by the number of butterfly and moth species they support. Another great resource are the Pollinator Partnership Ecoregional Guides which provide free PDF planting guides tailored to your ecoregion. You can also check out local native plant societies and conservation groups such as the Gary Oak Restoration Team, Native Plant Study Group and Satinflower Nursery who are all specific to Southern Vancouver Island and the Native Plant Society of B.C. which is province-wide. If you are looking for a local native plant society or organization in your area, you can check out the North American Native Plant Society's list of Native Plant Societies.

(Source: nwf.org)

Including keystone native plants in your garden has an outsized beneficial impact on local biodiversity. Even a single oak tree or a few clusters of native asters can provide critical resources for wildlife. Unlike exotic ornamentals, these plants have co-evolved with local species for thousands of years, making them an irreplaceable part of the ecosystem. Keystone native plants are more than just beautiful; they’re the backbone of the ecosystems we all depend on. By planting them, we aren’t just filling space in our gardens. We’re actively repairing the living networks that keep our landscapes thriving.