Native plants and support for pollinators in Canada

Canada is home to several hundred species of native bees — quite distinct from the European honey bee (Apis mellifera) introduced by settlers. These native pollinators maintain evolutionary relationships with specific plants: some plant species can be pollinated effectively only by local insects whose morphology matches the structure of their flowers. Introducing native plants into a residential garden directly helps maintain functional habitats for these insects.

Canada's native pollinators

Solitary native bees

Unlike honey bees that live in colonies, most Canadian native bees are solitary. They nest in soil, hollow stems, or small cavities in dead wood. Among the most common genera:

• Osmia (mason bees) — active early in spring, highly effective pollinators for fruit trees.
• Megachile (leafcutter bees) — use leaves from plants such as rose or alfalfa to build their nests.
• Halictus and Lasioglossum — small striped sweat bees, present in most Canadian gardens.

Native bumblebees

Canada hosts several species of native bumblebees (genus Bombus). Some species, such as Bombus terricola and Bombus pensylvanicus, are listed as of concern in several provinces due to population decline. Native plant gardens provide important substitute habitat in urban and peri-urban settings.

Butterflies

The monarch butterfly (Danaus plexippus), whose annual migration crosses Canada, depends exclusively on milkweeds (Asclepias spp.) as host plants for egg-laying and larval development. The disappearance of these plants from agricultural and residential landscapes is one of the factors identified in monarch population decline.

Structuring native plants for biodiversity

Early-blooming species (April–May)

The availability of floral resources at the start of spring is critical for pollinators emerging from dormancy. Species such as Aquilegia canadensis (Canada columbine), Mertensia virginica (Virginia bluebells), and Claytonia virginica (spring beauty) bloom before most exotic cultivars are in flower.

Summer-blooming species (June–August)

• Monarda fistulosa — particularly attracts bumblebees and certain butterfly species.
• Echinacea purpurea — visited by many native bees; seed heads feed goldfinches in autumn.
• Lobelia cardinalis — pollinated mainly by hummingbirds, present in Eastern Canada in summer.
• Asclepias tuberosa (butterfly weed) — monarch host plant, also attracts many butterfly and bee species.

Autumn-blooming species (September–October)

Late-season bloom is often overlooked in conventional gardens, but it is essential for pollinators building reserves before winter or migration. Symphyotrichum novae-angliae (New England aster) and Solidago canadensis (Canada goldenrod) are among the most important floral resources of this period.

Structuring a garden to maximize biodiversity

Beyond the choice of flowering species, several structural elements contribute to the ecological value of a native plant garden:

• Bare soil patches — many solitary native bees nest in the ground. Leaving a few unmulched areas in sunny, well-drained spots provides nesting sites.
• Stems and dead wood — leaving sections of hollow stems (elderberry, bee balm) and small pieces of dead wood supports cavity-nesting bees.
• Height diversity — combining species of different statures (ground covers, mid-height perennials, shrubs, native trees) multiplies the ecological niches available.
• Reducing impervious surfaces — paved areas limit ground-nesting sites. Minimizing these surfaces benefits soil-dwelling pollinators.

Native shrubs and trees: an often underestimated dimension

Native woody plants — shrubs and trees — constitute an even more important ecological resource than most herbaceous perennials, due to their size and longevity. Species such as Cornus stolonifera (red-osier dogwood), Sambucus canadensis (Canada elderberry), Viburnum lentago (nannyberry), and willows (Salix spp.) support a very large number of insect and bird species.