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Black Swallow-Wort Intiative

What is Black Swallow-wort? 

Black swallow-wort is an invasive, herbaceous, perennial plant in the milkweed family that is native to Europe.  This species is of special concern to us here in Northern Michigan because of its toxicity and ability to rapidly displace native vegetation. Monarch butterflies may mistake swallow-wort for milkweed and lay their eggs on the plant, which is toxic to the larvae. Many insects avoid feeding on swallow-wort plants because they are either toxic or distasteful; swallow-wort roots are toxic to mammals. 

Black swallow-wort grows rapidly and can cover or displace beneficial vegetation, including the plants in your garden! The seeds are easily spread by the wind, similar to how native milkweed seeds are dispersed. To learn more about black swallow-wort continue reading below. 

The history of a toxic invader 

Black swallow-wort was first cultivated in greenhouses in the mid-1800s in Ipswich and at the Harvard Botanical Garden, both in Essex County, Massachusetts. In 1864, an Essex County collector recorded it was “escaping from the botanic garden where it is a weed and promising to become naturalized.” History proved that the collector was right. Black swallow-wort is now in every county in Massachusetts and has spread into surrounding states as well as many northern Midwestern states, including our home here in Michigan. 

The history of black swallow-wort in northern Michigan is a little less clear. Anecdotally speaking, the spread of swallow-wort in the CAKE region is very limited - thus far primarily being found in or around the City of Petoskey. We don't know when, or exactly how swallow-wort got here, but one theory is that someone planted it as an ornamental plant and it escaped cultivation. 

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Project Partners

CAKE CISMA is teaming up with the Little Traverse Bay Bands of Odawa Indians and the Petoskey Parks department on this project. Treatment and survey funding has been graciously provided by the Little Traverse Bay Bands of Odawa Indians.

Pesticide Use 

We get a lot of questions about how we treat black swallow-wort, and why we use herbicides to do so. We appreciate the concern so many community members have about the environmental impact of herbicide use - it's important to ask these questions and we're more than happy to answer them. 

At CAKE CISMA we follow best management practices for each invasive species we work to control. Generally speaking, that means we want to do what's most effective and least environmentally detrimental when controlling each species. Sometimes that does mean using a chemical treatment. When it comes to swallow-wort, most mechanical controls (mowing, burning, digging, etc.) just aren't very effective at eradicating the plant long-term, and some can actually help spread the plant further. 


Our staff are registered or certified Michigan Department of Agriculture and Rural Development (MDARD) pesticide applicators and we're knowledgeable about treatment information. We always carry pesticide labels with us so landowners can read up on specifics prior to treatment if they wish to do so. With swallow-wort, we typically spot treat each individual plant. It takes longer, but this means we're spraying less herbicide overall and allows us to try to avoid any nearby plants.


Herbicide use on your property is always your decision. If you decide against treatment, we encourage you to remove all seed pods prior to when they open in the fall and dispose of them in a black garbage bag to prevent the spread of swallow-wort to surrounding properties and natural areas. 

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