Invasive SpeciesBlack swallowwort

Cynanchum louiseae
FOUND by gbh
Monhegan Island
ID Confirmed
Quality checked by gbh
Peer reviewed by
Field Notes
This is one of four observations that I'm sharing of suspected black swallowwort on Monhegan Island. This is one of the places where I observed this plant for the first time in 2012 (I do not remember seeing it in 2011 when I was here). It seems to be establishing itself in a garden protected by a rocky wall. It appears to be happily growing in and amongst the Rosa rugosa plant. This site is right downtown, if there is such a thing on Monhegan, right at the turn off the Maine road to go down to Swim Beach. Truck traffic could have helped to waft the seeds on their parachutes here from the other places where it is established. I'm really concerned about this plant being on Monhegan. I was talking with a friend about black swallowwort, and her comment was "oh, the plant that ate Cape Cod!" I hadn't heard that before...
Supporting Evidence
Photo of my evidence.
This photo shows a distinctive flower that matches the description of black swallowwort. It is dark purple, the five petals are as wide as they are long, the whole flower is small (these were almost half the size of my fingernails). For scale, there is a Rosa rugosa leaf in the upper left hand corner of the picture. You can also see the climbing, twining habit of the plant itself.
Photo of my evidence.
These two pictures show the top and bottom of a typcial-sized leaf. Using a ruler and my hand now to estimate (I didn't have a ruler with me), I'd say that the large leaves were 13 or so cm long (5 inches). The new leaves were purplish and very shiny. The older leaves were duller, but not hairy. On the right hand edge of the picture you can see flowers peeking out from behind another leaf - you can get a sense for their size from this.
Photo of my evidence.
This picture more clearly shows the twining, climbing habit of this plant. It's climbing up itself! This habit is completely consistent with black swallowwort. You can also see that the leaves are opposite, which is another characteristic of 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 43.764074 °
W -69.320197 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
Fish Beach turn, Monhegan Island
Trip date: 
Tue, 2012-06-12 10:50
Town or city: 
Monhegan Island
Type of investigation: 
Species Survey
Eastern Coastal


Thanks for keeping an eye out for this one, gbh! It is a bad actor.

Yes, indeed.

I've been looking out for this one ever since my dear friend Les Mehrhoff pointed it out to me years ago... I think I've seen it in Portland, too.