Dog-strangling vine, or, Cynanchum rossicum (Kleopow) Borhidi

In my post on October 26, about the third walk I took at KSR on August 23, I included this photo of a vine I didn’t recognize, and couldn’t remember seeing before:

and asked if anyone knew what it was. My thanks to Janet Inksetter and Helen Mills both, who told me it is dog-strangling vine, a perennial, non-indigenous plant of the milkweed family, first described (botanically) in the Kiev area of Russia, and thought to be endemic to the Caucasus and Black Sea region. It is now not only found but deemed invasive throughout southern Ontario, as well as in Connecticut, Massachusetts, New Hampshire, New York, and Wisconsin.

The vine is also known as European swallow-wort and pale swallow-wort, but dog-strangling vine is more vivid and memorable a name. It connects to the binomial term “cynanchum,” which is derived from Greek words meaning “dog” and “strangle” or “poison”. From what I’ve been able to discover there’s no record of the vine snaking out and snaring a dog, or any other animal, but it is possible it was used as an animal poison in the past, since it has toxic qualities.

In spite of the possible poison connection I think the name has a misplaced hyphen. The plant is a twining vine (twining left to right!) that winds itself around whatever it climbs, and eventually grows so densely that it strangles other plants, producing a monoculture. So “strangling-vine” is more accurate to its behavior. Where “dog” fits, in my scenario, is in the plant’s following at the heel of settler/immigrant culture: its origin in Ontario is likely as an escape from gardens. 

As the photograph above shows, the leaf is attractive, and since the vine grows thickly it would be attractive to gardeners. I read one account that suggested it was brought in for the fluffy seeds that were used for filler in life jackets during the war, but I haven’t been able to verify that. Although it grows less quickly in shaded areas—its native turf appears to be grasslands—it can grow almost everywhere and is commonly discovered in backyards, pastures, woodlands, and alongside streams.

Within the Toronto region dog-strangling vine grows throughout the Don and Rouge watersheds, along the Humber, and in most natural areas of the Oak Ridges Moraine, including KSR. There’s a good write-up tracing the species presence in southern Ontario and what was known (by 2007) of its spread and behaviour at

 http://www.rougepark.com/unique/reports/RP_DSV_Report_Dec07.pdf 

I went looking for that patch of the vine again a couple of weeks ago and found it. Here’s what it looks like now—

and in this form I do remember seeing it in both Sunnybrook Park and along the Rouge.

Like most non-native invasive plants, dog-strangling vine has no known natural controls. It spreads largely, and very successfully, by seed (germination plus or minus 50% in optimal conditions), but it also can move via rhizomes, and, as the Rouge Park report makes clear, its behaviour may have changed over time. 

If you do an internet search for Cynanchum rossicum you’ll find many pages warning of its ability to take hold and take over with what are expected to be dire consequences for species diversity. It does in fact constitute a threat to insects—Monarch butterflies being a particular concern because they lay their eggs on the plant, but the caterpillars can’t survive on it—as well as other plants.

An excellent species account is available at: http://www-personal.umich.edu/~rburnham/SpeciesAccountspdfs/CynarossAPOCFINAL.pdf

I asked Art Weis, the Director at KSR, about the vine and about the general practice here regarding invasive plants. Here’s what he said:

We are starting a co-operative project with Seneca College on dog strangling vine. It is getting to the point where some control measures will be needed to keep it out of the old growth forest. The first step with Seneca is to map its occurrence on the west side of Dufferin Street. However, we do not try and eradicate invasives because they offer potential research projects.

The mapping project will begin next June, in the area where I took these photographs. 

Quiet Pleasures

December 5, 2012. It was still dark when I woke this morning—what one expects in December. But a window sill in the bedroom seemed to be illuminated. I peered out and saw the moon high overhead, half-full, framed by the conifers that grow alongside the house. It had a faded rainbow ring around it, so I went outside to try and photograph it. I didn’t capture the ring, but did get a trace of the framing branches. Look closely and you'll see them.

Now (9:30 a.m.) snow is falling softly though the temperature is still above freezing. It began to fall, just an occasional flake, a few minutes ago while I was outside, photographing the old trees in back of this house, the ones that keep me company. Even as I’m typing it’s falling more thickly, lingering on the car but melting as it hits the ground. One of the pleasures of falling snow, more noticeable perhaps in the city, is the silence it creates.

Remembering that silence leads me to the quiet pleasures I’m finding in this house, domestic pleasures for the most part. Learning its sounds—I wondered before coming here what the house would sound like. Would its noises make me feel comfortable or nervous? It’s quiet, with few creaks and groans except the usual clicks as heat comes and goes. The furnace, when it comes on, makes a sturdy pair of hums, sounds that are warming in themselves. My city fridge is noisy, uttering a variety of whirrs and mutters and sometimes clunks. The fridge here whispers to itself.

The satisfactions of sweeping floors and putting things away so the kitchen counter is spacious when I come down in the morning is a pleasure. The dining room with its pine table and unrugged hardwood floor is another. I like to sit at that table facing the woods to write, as well as to eat. It’s solid and smooth.

My gleaming red kettle is, if not exactly quiet itself, a source of quiet pleasure—the ritual of making tea or coffee, hot cup then warming my hands as I savour the taste and the pause. I sometimes take my first cup of the day out onto the back porch so I can look at those old trees for awhile—another pleasure—without the window glass between us.

I’m not very knowledgeable about trees—a mix of pines and spruce, perhaps, is what gathers around the house, with three cedars across the front. I’ll have to get a tree book—or better yet find someone here who can tell me what I’m looking at. The trees immediately in back are old and not clumped close together; the space between them has allowed their boughs to stretch to amazing lengths. Most of their lower branches are bare and their tops are thin.

But one long pine bough I can see is covered with green and I like to watch it move and shift with the wind. The way conifers move makes me think of ruffled skirts shifting and twirling in a dance. A square dance perhaps, each waiting its turn.

The quiet pleasure of reading … the somewhat less quiet pleasure of writing … and best of all: staring out one window or another at the trees and weather, thinking vague thoughts from time to time—I spend hours doing that.