Swallowwort

 

(This 743rd Buffalo Sunday News column was first published on June 26, 2005.)

 

Get ready for another alien plant invasion.

 

If you think that weeds like purple loosestrife, Japanese knotweed, garlic mustard, celandine and common reed are bad, get ready for a newcomer that will prove far worse.

 

Consider what people report as swallowwort rapidly marches westward toward us.

 

Julie West lives in Henderson, New York, a community east of Lake Ontario near Watertown. "To me," she says, "it's like my land has cancer and I feel an overwhelming sense of helplessness as I watch swallowwort spread. When it first appears, it's very deceiving. It's just a plant here, a plant there, no big deal." But then, she says, over very few years it multiplies "until it is so thick it completely smothers everything. It twines together so you can hardly walk through it. Nothing else grows, not even grass. When it takes over an open field, there are no more wildflowers. No daisies, no dandelions, no milkweed, no Queen Anne's lace, not even chicory or thistles. It can climb eight to ten feet high. It will smother and kill juniper, honeysuckle and small trees."

 

Andrew Fowler, who manages a Christmas tree farm and nursery southeast of Rochester first came across swallowwort about seven years ago. He tells us: "It was when I was mowing a wooded slope one fall that I realized that this was no ordinary weed. The entire trail and surrounding woods was a mass of swallowwort six or seven feet tall, clambering over the undergrowth and up the trees, forming a tangled monoculture that quickly clogged the mower and sent clouds of seeds floating off into the surrounding woods." Soon it began to take over his Christmas tree plantation, growing, he says, "in the grassy aisles between the trees, crowding out everything else. I began efforts at controlling it by spraying herbicides, but nothing seemed to kill it. In fact, I believe that the application of herbicides actually gave it a competitive edge by killing off its competition. I don't know when the plant first arrived, but it has spread to every corner of our farm, in spite of my control efforts."

 

Rochesterian Michael Parker's malamute couldn't penetrate a field of swallowwort. No wonder one of its alternate names is dog-strangling vine.

 

This nasty alien is already here on the Niagara Frontier. For example, Charles deLaunders owns a lovely home on Main Road in Clarence. His gardens are being attacked by swallowwort. There are large patches on the escarpment behind his house and it has now spread to his front yard where it is climbing into his conifers. So far his attempts at control have met with little success.

 

Swallowwort belongs to the milkweed family. Like poison ivy it grows as an erect plant or a vine. Its oval three to four-inch leaves are opposite with pointed tips. To me the leaves of the upright plants give them an appearance much like swamp milkweed. The flowers are different, however. They are tiny five-pointed brownish-purple stars, only 3/8-inch across. They occur in clusters. These mature into parachute-equipped seeds in two to three inch slim pods. As with other milkweeds the pods open and the seeds disburse wind-bourn. Plants die back each winter, regrow in spring and flower in June and July followed by pod production from midsummer to fall. About 2000 seeds are produced by each square meter of plants.

(These tiny swallowwort flowers are only 3/8 inch across.)

 

The native range of swallowwort is Europe. It was first recorded in eastern Massachusetts in 1854, where it evidently escaped from gardens in the Cambridge area. It is now found in twenty states and several Canadian provinces.

 

Control of this weed is extremely difficult. Mowing, even several times each year, does not eliminate swallowwort, but when timed in July when pods have not yet matured can prevent further spread. If mowed earlier, the plants reflower. Powerful chemicals like triclopyrester and glyphosate should usually be applied by professionals. To eliminate small infestations dig out and remove the entire root crowns.

 

I hope that botanists and gardeners will organize to seek solutions before we are overrun. This emergency clearly indicates how shortsighted has been the dismantling of our cooperative extension services.-- Gerry Rising