Nectar and pollen plants attract pollinators for feeding, but host plants are what allow them to reproduce. A pollinator habitat without host plants supports transient visitors but does not build a resident population. Understanding which native plants serve as hosts for bees and butterflies — and which species depend on them — makes a meaningful difference in the long-term value of a backyard habitat.
This article focuses on host plant relationships documented for Ontario and eastern Canada, where species assemblages and plant communities are relatively well-studied compared to other parts of the country.
Host Plants vs. Nectar Plants
The distinction between host plants and nectar or pollen plants is important when designing habitat:
- Nectar and pollen plants provide food for adult pollinators. Most native plants serve this function to some degree.
- Host plants are plants on which insects lay eggs and on which larvae feed. Many bee and butterfly species are specialists — they can only complete their lifecycle on one plant genus or family.
Adding a species' host plant to your yard can be the difference between that species visiting occasionally and actually reproducing there.
Butterfly Host Plants in Eastern Canada
Several butterfly species found in Ontario and the eastern provinces have well-documented host plant requirements. The following are among the most commonly encountered species in residential settings:
| Butterfly | Host Plant(s) | Notes |
|---|---|---|
| Monarch (Danaus plexippus) | Asclepias spp. (milkweeds) | Larvae feed only on milkweed; A. syriaca and A. tuberosa are best options for residential gardens |
| Black Swallowtail (Papilio polyxenes) | Carrot family (Apiaceae): Daucus carota, Zizia aurea (Golden Alexanders) | Will also use parsley and dill in garden settings; Zizia aurea is the preferred native host |
| Canadian Tiger Swallowtail (Papilio canadensis) | Populus spp. (trembling aspen), Betula spp. (birch), Prunus spp. (wild cherry) | Tree hosts; suitable for larger yards or properties with existing native trees |
| Silver-spotted Skipper (Epargyreus clarus) | Legumes: Robinia pseudoacacia, Amphicarpaea bracteata, wild indigo | Readily uses Baptisia australis (Wild Indigo) as host in garden settings |
| Great Spangled Fritillary (Speyeria cybele) | Viola spp. (native violets) | Larvae feed at night on violet leaves; adults nectar on thistles and milkweeds |
| Painted Lady (Vanessa cardui) | Cirsium spp. (thistles), Malva spp., Antennaria spp. | Generalist; native thistles preferred over invasive species |
Native Bee Host Plant Relationships
Unlike honey bees, which forage on a wide range of plants, many native bee species are oligolectic — meaning they collect pollen from only one plant genus or family. These specialist bees are often the most efficient pollinators of their host plants and may be locally absent if the plant is not present in the landscape.
Selected Native Bee Host Plant Specialists in Eastern Canada
- Spring Beauty Mining Bee (Andrena erigeniae) — specialist on Claytonia virginica (Spring Beauty)
- Squash Bee (Peponapis pruinosa) — specialist on Cucurbita spp.; will use ornamental gourds
- Sunflower Mining Bee (Andrena helianthi) — specialist on Helianthus spp. (native sunflowers)
- Bergamot Bee (Anthophora terminalis) — specialist on Monarda spp. (wild bergamot, bee balm)
- Trout Lily Bee (Andrena erythronii) — specialist on Erythronium americanum (trout lily)
Milkweed Species for Monarch Habitat
Milkweed deserves particular attention in any eastern Canadian pollinator garden. The Monarch butterfly's larval survival depends entirely on the presence of Asclepias species. Three native milkweeds are suitable for residential garden use in Ontario and eastern Canada:
- Common Milkweed (Asclepias syriaca) — The most widespread native milkweed; spreads by rhizomes (plant where spreading is acceptable); zones 3–9; blooms June–August.
- Butterfly Weed (Asclepias tuberosa) — Does not spread aggressively; orange flowers are highly attractive to a broad range of pollinators; tolerates dry conditions; zones 3–9.
- Swamp Milkweed (Asclepias incarnata) — Suitable for wet areas or rain gardens; deep pink flowers; zones 3–6; attractive to bumble bees.
Non-native tropical milkweed (Asclepias curassavica) is available in nurseries but is not recommended for outdoor planting in Canada. In regions where it does not die back naturally, it can disrupt Monarch migration patterns. Native milkweed species are preferable in all cases.
Native Trees and Shrubs as Host Plants
Trees and shrubs support far more insect species than herbaceous plants. Research by entomologist Doug Tallamy has documented that native oaks (Quercus spp.) support several hundred caterpillar species alone. While not every yard can accommodate a mature oak, even a young tree provides measurable habitat value within a few years of planting.
| Native Tree/Shrub | Key Pollinators/Species Supported | Notes |
|---|---|---|
| Quercus spp. (Native Oaks) | Hundreds of moth and butterfly species; many native bees forage on oak pollen | White Oak and Bur Oak are most suitable for Ontario conditions |
| Salix spp. (Native Willows) | Critical early pollen source; Willow specialist bees (Andrena spp.) | Pussy Willow blooms earliest of any native tree in zone 5 |
| Prunus virginiana (Chokecherry) | Spring Azure butterfly; numerous bee species forage on pollen | Multi-season value: flowers in spring, fruit in late summer for birds |
| Ceanothus americanus (New Jersey Tea) | Summer Azure butterfly; specialized bumble bee foragers | Native shrub; fixes nitrogen; tolerates dry, rocky soils |
Purchasing Native Plants in Ontario
When sourcing native plants, it is worth verifying that plants are genuinely native to the local region rather than cultivars bred for ornamental traits. Some cultivars with modified flower structures — particularly double-flowered varieties — may have reduced pollen or nectar availability. Species-type plants or straight native species are preferable for pollinator habitat. Ontario native plant nurseries and conservation authority plant sales are reliable sources for region-appropriate stock.