Danaus plexippus (monarch butterfly)
Here’s a detailed breakdown of the ecological role of Danaus plexippus (monarch butterfly) and the best native host plants to support them, especially in the Midwest/Great Lakes region:
Ecological Role of Danaus plexippus
1. Pollinator
Adult monarchs feed on nectar from a wide variety of flowers, transferring pollen as they move between blooms.
While not as efficient as bees, monarchs contribute to the pollination of native prairie and meadow plants, including asters, goldenrods, and milkweeds.
2. Keystone Species in Food Webs
Monarch caterpillars are herbivores that feed exclusively on milkweed (Asclepias spp.), sequestering toxic cardiac glycosides that deter most predators.
Some predators (e.g., certain birds like black-headed grosbeaks, orioles) and parasitoid wasps have evolved to tolerate or exploit monarchs as a food source.
Their presence supports higher trophic levels, providing food for invertebrate and avian predators during both larval and adult stages.
3. Migratory Phenomenon
Monarchs are central to one of North America’s most remarkable migrations, traveling thousands of miles between breeding grounds in the U.S./Canada and overwintering sites in Mexico (Oyamel fir forests) or coastal California.
This migration links ecosystems across an entire continent, making them indicators of large-scale ecological health and connectivity.
4. Indicator Species
Population fluctuations reflect habitat quality, climate change impacts, and pesticide/herbicide use across North America.
Declines in monarch numbers signal loss of native prairies, pollinator meadows, and milkweed populations.
Habitat Needs
Monarchs require two major habitat components:
Larval host plants (milkweeds) for egg-laying and caterpillar food.
Nectar plants for adult energy, especially during migration.
Best Native Host Plants (Milkweeds)
Milkweeds (genus Asclepias) are the only plants monarch caterpillars eat. For the Midwest/Great Lakes (including Illinois, Michigan, Wisconsin), the following are most suitable:
Top Host Species
Common Milkweed (Asclepias syriaca)
Tall, clumping; thrives in open fields, roadsides.
Extremely high egg-laying preference.
Widely adaptable; tolerates dry to moist soils.
Butterfly Milkweed (Asclepias tuberosa)
Bright orange flowers; highly attractive to both monarchs and other pollinators.
Prefers dry, sandy, or well-drained soils.
Great for garden use due to non-aggressive spread.
Swamp Milkweed (Asclepias incarnata)
Pink flowers; thrives in wetter soils, rain gardens, and near ponds.
Excellent nectar source for migrating adults.
Whorled Milkweed (Asclepias verticillata)
Narrow leaves, delicate white flowers.
Good for dry, sandy, or poor soils.
Blooms later in summer, extending food availability.
Poke Milkweed (Asclepias exaltata)
Woodland edge species; tolerates part shade.
Good option for semi-shaded garden edges or woodland restorations.
Supporting Plants Beyond Milkweed
Nectar Sources
To fuel adults (especially migrants), include native flowering plants blooming spring–fall:
Early Season: Wild columbine (Aquilegia canadensis), spiderwort (Tradescantia ohiensis).
Summer: Purple coneflower (Echinacea purpurea), blazing stars (Liatris spp.), bee balm (Monarda fistulosa), black-eyed Susan (Rudbeckia hirta).
Fall (critical for migration): Aromatic aster (Symphyotrichum oblongifolium), New England aster (S. novae-angliae), goldenrods (Solidago spp.).
Ecological Planting Tips
Diversity: Mix at least 2–3 milkweed species with staggered bloom times and habitat tolerances.
Clumps, not singles: Plant milkweeds in groups (3–5 or more) for easier detection by monarchs.
Chemical-free: Avoid pesticides/herbicides; monarchs are sensitive to both direct toxins and reduced milkweed availability.
Continuous nectar: Provide blooms from May through October to support breeding adults and migrants.
Landscape integration: Pair milkweed with other prairie natives (e.g., prairie dropseed, little bluestem) for structural diversity and ecological resilience.
Conservation Significance
Monarch populations have dropped by ~80–90% in the last two decades, largely due to habitat loss and pesticide use.
Planting native milkweed and nectar sources is one of the most direct ways to aid their recovery, especially in urban/suburban areas where native prairies have been lost.
