Black swallow-wort: A nasty invader

Matt Smentana Wednesday, 10 June 2020

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Years ago, a seed propelled by wind landed at Clearpool Model Forest in Carmel, NY. Called black swallow-wort, this plant began to grow, flower, and before long, one plant became a booming metropolis. By most accounts, this is a great example of the success of life. Unfortunately black swallow-wort is a foreign plant invader known to decimate forested areas by forming dense thickets which overtake native plants.

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Some black swallow-wort, looking mean and green, at Clearpool Model Forest.

As private landowners, we have to devote our time and money to a host of issues, most of which are difficult to prioritize. Here at Clearpool, having a biodiverse forest and ensuring public access to our trail system is very important to us. After surveying all areas of the swallow-wort invasion, we determined that our top priority was Blue Meadow, a section of our property with a uniquely open canopy along the trails. The area is also used by many of our education programs and overlooks one of the reservoirs supplying New York City’s drinking water.

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The Blue Meadow trail section at Clearpool.


The Blue Meadow was likely invaded by swallow-wort around five years ago. At the time, we tried mechanically treating the area by installing dark tarp on the ground and letting the sun eliminate plants and the seed bank, a technique called solarization. However, due to the area’s rockiness, the mechanical efforts were unsuccessful. Two summers ago, we explored the possibility of chemical treatment and decided to contract the expertise of regional invasive management group, Trillium.

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Trillium technicians with backpack sprayers treating the black swallow-wort.

On the first day of treatment, I got to see the crew in action and we talked a bit about some of the opportunities and challenges in managing invasives. Swallow-wort can look very similar to other species like poison ivy and oriental bittersweet, making surveying and management even more difficult. The crew did a fantastic job spraying all the affected areas and we quickly saw results from their hard work. Another treatment was applied that summer and then we blanketed the area with native seeds — I cannot wait to see what grows here in the future!

Additional resources:
New York Invasive Species (IS) Information about black swallow-wort
My Woodlot Activity: Control Invasive Plants

About the Author: Matt Smetana is the Model Forest Facilitator at Clearpool Model Forest in Carmel, NY.

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