Tropical Milkweed

Asked June 10, 2015, 12:41 PM EDT

Can you tell me why it is unsafe for the monarch butterfly if I were to plant tropical milkweed?

Sussex County Delaware

1 Response

Tropical milkweed (Asclepias curassavica) is not native to the U.S. It is adapted to grow year-around, Hardy in Zones 8 – 11. These plants continue to flower and produce new leaves throughout the fall and winter, until a freeze event, while most native milkweeds die back. Potential negative effects on monarchs include 1) continuous breeding on tropical milkweed throughout late fall and winter can lead to higher levels of protozoan infection, and 2) availability of milkweed during a time that it is not naturally available, can interrupt the normal migration and breeding patterns.

To support healthy monarchs, plant native milkweeds whenever possible. If you have tropical milkweed cut it back starting in October if it does not die back on its own and consider replacing with native plants.

To learn more see:

University of Minnesota Monarch Lab -

Monarch Joint Venture – a partnership of federal and state agencies, non-governmental organizations and academic programs, including the University of Minnesota