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Invasive vine spotted in northern Michigan poisons monarch caterpillars

close up of plant with purple flowers
Michigan Department of Natural Resources

Officials in northern Michigan are working to remove an invasive plant that poisons monarch butterflies.

The black swallow-wort is a vine with heart-shaped leaves and small, dark purple flowers.

Monarch butterflies often lay their eggs on it, but the caterpillars are poisoned when they hatch and begin to eat the plant.

It grows on the side of the roads, and in pastures and gardens. 

The Traverse City Record-Eagle reports it's been spotted in Kingsley, a village outside of Traverse City.

The Michigan Department of Natural Resources says its sap is toxic to mammals and insects. The plant also has pathogens that stop other plants from growing around it.

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