Tangled In Dog Strangling Vine

TANGLED IN DOG STRANGLING VINE

Wednesday, May 09, 2007 (Napanee Beaver)

Friday, May 11, 2007 (Picton Gazette)

It’s an annual ritual that my wife and I undertake every spring, in late April. We load up the lawn mowers and pruners and head for Prince Edward Point where we groom the trails through the Point Traverse Woods. This is a necessary exercise each year as encroaching prickly ash, fragrant sumac and other plants soon pop up in the trails that birders have traditionally followed every year in their search for migrating birds. If done every year, it is only a four hour job. This year, however, it took a bit longer due to the lawn mower becoming ensnared repeatedly by another plant which lay dead, its grey intertwining stems carpeting the paths in isolated areas, and still clasping onto trail side bushes. This was last year’s growth of dog strangling vine, and already, this year’s dark green growth was starting to peek through the vegetated trash of last summer.

Most of us recognize milkweed when we see it, and as kids, we learned of its value to Monarch butterflies. But there are other milkweeds out there too, some of them less familiar to us, including swamp milkweed and the gorgeous flowers of the butterfly-weed. It takes a bit of searching to find the latter species, but I have found it blooming at the Menzel Nature Reserve, 18 km north of Deseronto. And some milkweeds are highly scented when in bloom. The fragrance of common milkweeds in flower is not unlike a hedgerow of lilacs in full bloom. In the eyes of naturalists, all good plants that can do no wrong.

However, dog strangling vine is the black sheep among the several species that regularly occur in the area. As a non-native species, it is becoming a serious threat to native plants in the area. More properly known as black swallowwort, the plant is turning up everywhere. In the Point Traverse Woods, it is almost as invasive as the garlic mustard that grows here. Even Main Duck Island, located some 12 miles out in Lake Ontario, has offered no escape from this plant. It grows there too. The only resemblance to the milkweed family to which it belongs is the slender floss-filled pods which droop from the spindly vines. In the spring its dark green leaves appear quite innocent as they dot the open meadows, but by late this month the plant will have emerged into three-foot long vines that search for objects to wrap around. When these are not available, they wrap around each other, often in such a tangled mass that walking becomes difficult; hence, the well chosen name, dog strangling vine. Where it grows, nothing else stands a chance.

Black swallowwort is native to southern Europe, and was brought into Canada during the Second World War to be evaluated as a possible filling for life jackets. Its seed is very buoyant which likely accounts for it being found on remote islands. Its botanical name, Cynanchum, is from the Greek, kyon means dog and ancho to strangle, hence its common name, dog strangling vine, but there are no reports of it strangling a dog; plants, however, are another story. The plant escaped from research plots and is now established at several locations in Ontario and Quebec. Few native plants can compete with it for space and even woody plants succumb.

Its current habitat is gullies, roadsides, fencelines and waste areas, but once established it’s difficult to eradicate, even with the use of weedkillers. Seeds are spread by the wind, like those of milkweed, so it can spring up almost anywhere. A few years ago, the plant had minimal distribution, but it’s now more widespread.

We know that changes are a natural part of our landscape. We have seen these changes evolve at Prince Edward Point and Point Traverse at the southeastern most tip of Prince Edward County. Spreading prickly ash and wild lilacs have encroached some open areas of this now famous birding location, providing even more attraction to the swarms of songbirds that descend on this point of land each spring. In some areas, the makeup of species has changed too. The once open savannas where bobolinks once frolicked are now homes to other species including clay-colored sparrows. Although the thin soil has resulted in little change to the trees that grow here, invasive plants such as garlic mustard and black swallowwort have all but replaced the carpets of blue phlox and communities of columbines that once dominated the woods when I started actively birding this southeastern most tip of Prince Edward County in the early 1960s.

It has been interesting over the years to see the gradual changes that have taken place at this Point Pelee of eastern Ontario, and the species that have evolved with it. Although regarded as invasive species, both the garlic mustard and the black swallowwort will continue to crowd out the plants we knew so well here 40 years ago. However, the warblers, vireos, flycatchers, thrushes and tanagers that call this area home for a few days each spring as they move northward, seem to care little by the ground cover, for it is the insects which these trees and plants collectively attract that interest the spring migrants. Perhaps in another 40 years, the invading plants will have run their course, and a new cycle of plants will begin – perhaps even the return of the blue phlox and columbine.