Invasive SpeciesBlack swallowwort

Cynanchum louiseae
FOUND by gbh
Monhegan Island
ID Confirmed
Quality checked by gbh
Peer reviewed by
Field Notes
I made this observation on my way to the start of the Alder Trail, where I think I saw black swallowwort last year. I was sad to see the suspicious plant on both sides of the road here. There was more on the sunnier side of the road, the side with the truck and boat. There were plenty of old stems and the remains of old seed pods (they looked like grey, dried out, opened pods of a similar shape to milkweed pods, but narrower and more delicate) mixed in with the weeds, so this plant was apparently here last year as well. There is, for Monhegan, a fair amount of truck/ vehicle travel along this road. I wouldn't be surprised to learn that this contributed to the spread of this species along the length of the road.
Supporting Evidence
Photo of my evidence.
This photo shows the dark color, five short and fat petals, and small size of the flowers, which are characteristic of black swallowwort flowers. This image also shows the opposite arrangement of the leaves on this plant, another characteristic of black swallowwort.
Photo of my evidence.
This image shows the old vines from last year being lifted up by this year's growth. You can also see the tall, reaching, curling ends of the plant that makes them look like they'd be great climbers (black swallowwort is a climbing vine). This image shows the oppositely arranged leaves, which is a characteristic of black swallowwort. And finally, you can see that the leaves are fat blades/ elongated, pointy ovals, which is the shape of black swallowwort leaves.
Photo of my evidence.
This image shows last year's vines more clearly, including the remains of last year's seed pods. Black swallowwort seed pod parts persist on the vine into the following year.
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 43.764790 °
W -69.318151 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
Monhegan Island, road to Alder Trail
Trip date: 
Mon, 2012-06-11 11:15
Town or city: 
Monhegan Island
Type of investigation: 
Species Survey
Eastern Coastal


You have great evidence and great field notes, after looking at your pictures I remember seeing that plant on the side of the road on my way to Bangor, ME.

Thanks, smokeythebear, for finding my species observations and liking my evidence and field notes!

I didn't know that black swallowwort was in Bangor - you should do an observation of it! Not many people in Maine have looked for it, at least not many people on Vital Signs. It would be interesting to get a lot of people looking for it all over the state.

Thanks for your comment!


Great job. You did a thorough observation. Your evidence is clear and builds a strong case. The pictures are also amazing.

I like how you are using your knowledge from past years to better understand this year's growth. Understanding the change that you have seen over the past year, how do you think the plant might continue to spread? Is there anything that could be done to stop or slow the plant's growth?

Thanks, Mainer95.

I have two more observations of this plant to upload - thanks for the encouragement!

What could be done to stop the spread of this plant, you ask... well, I've thought about this. A major hand-pulling effort could really dent the population, even now. Or, barring that, removal of seed pods after they mature but before they ripen could help slow it. The challenge of Monhegan is that the people who live out there, generally, are as busy as anyone and don't have hours and hours to volunteer. The people who visit don't necessarily know enough to know what action to take, despite their often very deep love and commitment to the place. I think to be successful any effort would need an on-island champion, maybe in the form of the Monhegan Association Fellow, to educate and coordinate efforts.

Any of that would have been easier last year and will only get harder next... Tough.

Thanks for looking at my observation!


You are most definitely right. Controlling the spread of this plant would be difficult (and that's probably an understatement). I recommend checking out this document ( It discusses some removal methods and a little bit about the plant. I find it interesting because of how the plant's main growth is below ground. It seems like you only see that in grassland plants these days. So, in order to remove the plant, you would have to do some intense digging. You could do it by yourself, but it would definitely take a lot of time. Maybe you could gather a bunch of friends and have a digging party on a Saturday afternoon? :) Bring some food and everybody will come! Getting people together anywhere is hard, and it is especially difficult to motivate a group to give up their free time to go and dig up plants.

I am not sure if this is a feasible idea, or if it would even work, but I know that if a pond has a lot of nuisance vegetation, the pond owner should just cover it with a black tarp for a long time (like the entire growing season) to kill off the plants. This might work with your plant, but because its main growth is below ground, it might be unsuccessful. And, a bunch of black tarps would not be the prettiest thing on the otherwise beautiful island!

You are right that it will only get harder. I would work on trying to get a group together to go and dig it all up. This seems like the best way to approach the problem, but you still run the risk of missing one or two seeds that will then grow up into new plants in the following year. As you know, prevention is always a lot easier than removal, so I would focus on preventing the spread of the plant.

Thanks for watching out for the invasives on the island. Keep up the great work!!