Wild Monarch Butterfly Larval Host Plant Selection

Monarch butterfly larval success depends on the availability and quality of milkweed host plants, and not all milkweed species equally support larval welfare.

Key Facts

Monarch caterpillars feed exclusively on milkweed (Asclepias species), sequestering toxic cardenolides for predator defense
Over 100 milkweed species are native to North America, with regional adaptation to specific Asclepias species
Tropical milkweed (Asclepias curassavica), commonly sold in nurseries, is non-native and problematic in warm climates
Tropical milkweed does not die back in winter in the south, disrupting monarch migration cues
Protozoan parasite Ophryocystis elektroscirrha (OE) can build up on non-native milkweed that persists year-round
Native milkweed planted in appropriate ecoregions supports larval development and supports migration triggers
Planting regionally appropriate native milkweed is one of the highest-impact monarch conservation actions available

Welfare Considerations

Larvae forced to develop on inappropriate milkweed species show reduced survival and development rates. OE parasite loads acquired on non-native milkweed cause adult monarchs to have reduced flight capacity and lifespan. Plant selection for pollinator gardens directly affects the welfare of the larvae that develop on them - native species matched to your ecoregion are the welfare-optimal choice.

What You Can Do

Plant regionally appropriate native milkweed species from the Xerces Society regional guide
Avoid tropical milkweed (Asclepias curassavica) in southern states where it persists year-round
Cut back any tropical milkweed to ground level in fall if you live in a mild climate
Monitor milkweed for OE spores if you participate in monarch citizen science programs
Support native nurseries that grow regional milkweed species appropriate for your area