Figure 1. A monarch butterfly on a grey-headed coneflower (Ratibida pinnata).
In an ecosystem, certain plants play a vital role. Like the pillars that support a building, they help an entire community find shelter, food, and stability.
These species, called keystone plants, support a large part of the local food web. Their importance goes far beyond what their simple presence might suggest.
What Is a Keystone Plant?
A keystone plant is a native species whose influence on the ecosystem is fundamental. The concept is inspired by architecture: just as the central stone of an arch holds the structure together, keystone plants support the stability of ecological networks. Where they are absent, insect diversity and abundance decline, weakening the entire food chain.
Research by entomologist Douglas Tallamy shows that this pattern repeats across all North American landscapes studied so far. In every ecosystem analysed, about 5 % of native plant genera alone support 70 to 75 % of local caterpillar species of butterflies and moths. These caterpillars form an essential part of the diet of many animals, especially insect-eating birds during the nesting season. A small number of plants is therefore enough to sustain a major portion of biodiversity.
For example, native genera such as oaks, goldenrods, and asters can each nourish dozens, sometimes hundreds, of insect species depending on the region.
Why Are They So Important?
Keystone plants provide essential resources: nectar, pollen, foliage for caterpillars, shelter, and breeding sites. They evolved alongside local wildlife, which makes them particularly effective at supporting productive and healthy habitats.
When they disappear, insect diversity and abundance drop drastically. Since insects lie at the heart of food chains, the entire ecosystem becomes more fragile. A native landscape can better support biodiversity when it includes certain keystone plants, because they play essential roles in maintaining ecological networks.
This demonstrates that even a small landscape can play an important role if it includes these essential species.
Protecting Local Biodiversity: A Concrete Action
To create spaces that truly benefit wildlife, it is crucial to integrate keystone plants into landscape designs. Their presence increases the environment’s capacity to support caterpillars, butterflies, specialist bees, and insect-eating birds.
Keystone plants are a key to reversing biodiversity decline. Introducing these plants into a garden means offering insects an irreplaceable source of food. A few well-chosen plants can support dozens of caterpillar species and, as a result, all the birds and pollinators that depend on them.
Protecting biodiversity often begins with small, accessible actions. By choosing keystone plants adapted to your region, you immediately increase your space’s ability to welcome and nourish wildlife. There is no need to transform the entire garden: a few well-placed species can make a real difference for supporting the insects and birds that rely on them.
Which Keystone Plants Should You Choose?
To discover the native keystone species available in our catalogue, explore our keystone plant collection and turn your landscape into a true refuge for biodiversity.
Figure 2. A patch of black-eyed Susan (Rudbeckia hirta).
Sources
Espace pour la vie. (2024, November 27). Les espèces-clés de voûte : des piliers de la nature. Biodôme / Espace pour la vie. https://espacepourlavie.ca/blogue/les-especes-cles-de-voute-des-piliers-de-la-nature
National Wildlife Federation. (n.d.). Keystone Plants by Ecoregion. https://www.nwf.org/Native-Plant-Habitats/Plant-Native/Why-Native/Keystone-Plants-by-Ecoregion
Tallamy, Douglas W. (2020). Nature’s Best Hope: A New Approach to Conservation That Starts in Your Yard. Timber Press.