Invasive SpeciesBlack swallowwort

Cynanchum louiseae
FOUND by gbh
ID Confirmed
Quality checked by gbh
Peer reviewed by
Field Notes
Last year I noticed a climbing vine with small, milkweed-like seed pods at this location. When I described this to botanically inclined friends, they suggested that maybe it was a swallow wort. I went back this year to document this suspicious vine. The shoots are still rather short (about 18 inches high) with no evidence yet of flowering, so it's quite difficult to identify (at least for me!), but I'm saying that I think I saw black swallowwort because I'm concerned that it might be and I want someone to check up on it! I found the plant just about 20-30 feet from the western trailhead for the #6 trail. It's on both sides of the trail there, with lots of new shoots. I spotted additional shoots, in lesser density, for the next 100+ feet as I walked east on this trail from this location. I did not draw a sketch, but I have uploaded an extra picture here. This image shows the previous year's growth, with the seed pod shells clearly visible. Note that i'm not sure about the exact latitude and longitude of my study site. I used an online tool to get the coordinates, but the map wasn't very good so I couldn't pick out my spot as precisely as I would wish. I am sure about the trail number and the distance from the road.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
I am suspicious that this is black swallowwort because the leaves are dark green, ovate/oblong, and pointed. The shoots are also growing up between the remains of last year's viny growth. In last year's growth there are remains of milkweed-like seed pods. You can't see it here (I had too many pictures to upload!), but I did break a stem. The sap was not milky. says that the sap of black swallowwort is not milky.
Photo of my evidence.
This photo shows a closer view of the shoots. You can clearly see the opposite arrangement of the leaves, and their pointed oval shape. The leaves were smooth and shiny. The very edges of the leaves look like they have tiny hairs on them. It was a foggy morning - the tiny hairs may look more prominent because they had some moisture attached. says that black swallowwort shoots grow in clumps. This picture clearly shows a clump. This was pretty typical of what I saw.
Photo of my evidence.
This picture shows the underside of the leaf. I heard from a scientist last weekend that the underside of leaves is being used more and more for identification. I found one description of black swallowwort ( that said that the undersides of the leaves have prominent veins. That is certainly true of the specimen in my photograph. You can just see the tip of my thumb for reference. This leaf was approximately 6 cm long and 4 cm wide.
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 43.763700 °
W -69.316350 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
Monhegan Island, trail #6
Trip date: 
Sun, 2011-05-29 10:00
Town or city: 
Type of investigation: 
Species Survey
Western Coastal


Great pictures that go nicely with the evidence. Nice work!