Invasive SpeciesBlack swallowwort

Cynanchum louiseae
FOUND by gbh
Monhegan Island
ID Confirmed
Quality checked by gbh
Peer reviewed by
Field Notes
I had the good fortune to be out on Monhegan Island for a few days. I was really concerned to note that the plant that I'm pretty sure is black swallowwort is now in several places on this special island. A year ago when I was visiting I only saw it in one place, near the town-end of Trail 6 (I have an observation of that spot to post this year). I saw this plant in several areas around the lighthouse, but I'm documenting it in the place where it was most abundant. It was growing just on the edge of where the lawn is mowed and into the "rough" area downslope from the lawn. It's been a very wet spring (it rained some 8+ inches in the ten days before my visit to Monhegan).
Supporting Evidence
Photo of my evidence.
I think this plant is black swallowwort because the flowers are small, dark purple, and five-petaled, with petals as fat as they are long. I didn't have a ruler so I didn't measure the flowers, but they were about as small as my fingernails (smaller than my thumbnail!). This is what the flowers of black swallowwort look like in images that I've found online (, for example). I don't think this is pale swallowwort because the flowers are darker and petals are shorter than pale swallowwort.
Photo of my evidence.
I think this plant is black swallowwort because the leaves are shiny (young ones, at least), smooth-edged, elongated oval-shaped that are arranged in an opposite growth habit. These characteristics are consistent with descriptions that I've found online of black swallowwort.
Photo of my evidence.
I'm uploading my method picture again to point out the tops of the plant I observed. There was nothing here for the plant to climb, but the tops of the taller plants have long, reaching growth that reminds me of oriental bittersweet and makes me think that this plant would be a good climber. Black swallowwort is a climbing vine. Further evidence that what I saw was black swallowwort.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Cynanchum louiseae
Common name:
Black swallowwort
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 43.764699 °
W -69.316435 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
Monhegan Island, near lighthouse
Trip date: 
Thu, 2012-06-07 14:45
Town or city: 
Monhegan Island
Type of investigation: 
Species Survey
Eastern Coastal
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