I had a garden open house yesterday for a local gardening group. It was a beautiful day and I was enjoying the visitors, or at least I was until one of them mentioned that I had the dreaded ‘dog strangling vine’. News to me! I have never had it before. I asked to see it and a few guests followed us to one of my clematis arbors. They pointed to evil villain.
I smiled and told them that this was a precious seedling I had grown a few years ago. I thought I had lost it during the winter, but luckily it survived. It even flowered with very small dark red/brown flowers. I mean very small! It was now making seed pods – nice long slender pods. I was very proud of my plant.
The name of the plant was Periploca sepium, or at least that was the name of the seed package when I got it from a seed exchange.
By now there were 6 or 7 people standing around and except for me they were all convinced it was the dog strangling vine (DSV). Then one lady stepped forward, feeling the leaves, she said, “it might not be the DSV, the leaves are too thick.” They all agreed that if it was the real DSV it would have spread much more in the couple of years that it was in the ground. It gave me at least some hope.
Everyone went home and I started doing some research. I find that following a problem like this always teaches me something. This occasion was no exception.
I first looked up Periploca sepium. Turns out this plant is a vine, it has a 5 part flower, and it has leaves and seed pods just like my plant. Guess I was right and the others were wrong!
I also looked up DSV – I knew about the plant but had never actually seen it. It is an invasive plant that is taking over in Ontario and much of North America. What I did not know is that DSV is actually two different species; Cynanchum rossicum and Cynanchum louiseae. The two species are similar in their growth habit and a description of the plants is very similar to P. sepium, namely a vine with small 5 part flowers, shiny opposite leaves and long slender seed pods. Maybe the others were right?
The most common DSV around here is C. rossicum. It has pale colored flowers so that is not a match. That’s good news – at least if I am growing an invasive weed at least I am growing the ‘less common’ one.
The flowers of P. sepium are about 2 cm wide, and mine are much smaller, so it looks like the name is not correct. I did find another Periploca; P. graeca and the flowers look a lot more like mine. I also found both plants for sale on the net so they must be garden worthy!!! However, both Periploca have seed pods that join at the tip. The seed pods form in a pair and the end farthest from the stem stays joined while they are forming. Given that fact, I don’t have a Periploca. It was not looking good.
On closer inspection Cynanchum louiseae seems to be a good match for my plant. I am the proud parent of an invasive species. I guess I won’t collect seed from it for this year’s seed exchange.
This experience illustrates a number of issues in the gardening world. Plants are easily mislabeled. I am sure the donor of the seed believes they were donating seed from a rare plant. Without my visitors I would have collected seed and passed it along.
As gardeners we know a very few plants and we should be careful with identifications. For example the genus Cynanchum has 300 species. I have only checked 2 of them, so I could in fact have something quite rare – one of the other less known species.
Most important of all – don’t be afraid to tell your garden host about a problem in the garden. I am very thankful someone said something yesterday. I learned something, and I may be able to avoid another plant invasion on my property.
Dreams of riches selling my special plant are dashed!! So sad.
PS. DSV does not strangle dogs; maybe a squirrel or two, but not dogs.
1) Photo Source: Robert Pavlis