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Hunting a colorful enemy in the yard

Invasive Asian bittersweet vine will wrap itself around healthy trees until it chokes them. Fall is a good time to kill it. Invasive Asian bittersweet vine will wrap itself around healthy trees until it chokes them. Fall is a good time to kill it. (John Lynch/New England Wild Flower Society)

I'm not usually in favor of plastic plants. But I was relieved to see a neighbor's harvest table decorated with imitation orange and red bittersweet berries, since the state of Massachusetts, just this summer, made the sale of real bittersweet, even in holiday decor, illegal.

These berries aren't poisonous to people, but they do kill forests. They've been in this country almost a century but have suddenly reached a tipping point. Everywhere you look, this Asian vine is clambering up trees and strangling them. Last week, I was walking a young couple around a wooded lot they'd bought in Milton, and I saw their expressions switch from excitement to alarm as I explained that the yellow fall foliage they were admiring was not leaves on the trees, but leaves on the bittersweet vines that had overwhelmed their forest canopy. Invasive plants are like that, hiding in plain sight - until you learn to recognize them.

Fall is the time to go on a hunting expedition to keep bittersweet from getting a foothold in your yard. Since the berries are spread by birds, it can sprout anywhere, even if no other vines are nearby. Bittersweet is also easier to recognize now because the rounded leaves, which end in points, yellow and stay on the vine into November after other leaves have dropped. And the red-orange berries are real standouts. They dangle in clusters surrounded by yellow round casings, sometimes 60 feet overhead. So look up.

Then, take pruning shears and cut every ropey stem that is growing up into that tree (except the trunk of the tree itself). Paint the fresh cuts with Brush-B-Gon to keep them from sprouting again. Don't try pulling the severed bittersweet vines out of trees. This can just break off entangled tree limbs and spread those dangerous berries around. Once cut off from its roots, the bittersweet top growth will die and disintegrate in place, freeing the tree it had entombed.

Small vines can be hand-pulled from the soil. The roots are tell-tale orange. But any bits of root that break off underground can start new plants, so larger vines with extensive roots must be poisoned.

"Now is a good time to apply herbicides, preferably triclopyr (Brush-B-Gon) on the cut stem with a drip bottle or sponge applicator," says Ted Elliman of the New England Wild Flower Society. "Triclopyr is more effective than glyphosate (Roundup) for treating oriental bittersweet." Though Brush-B-Gon can also be sprayed on leaves any time during the growing season, he says, bittersweet is easiest to kill in the fall when the sap is returning to the roots.

For the same reason, this is also a good time to dispatch invasive shrubs such as barberry, burning bush, glossy buckthorn, and multiflora rose. Elliman advises hatcheting a cut to their trunks and painting the cuts with a 25 percent solution of Rodeo herbicide. "The poison is sucked straight down to the root," he says. And The Weed Wrench Co. of Oregon (877-484-4177) sells excellent levers that mechanically pop invasive shrubs out of the ground without use of poisons.

A $15 "Field Manuel of Invasive Plants for the New England Region" or a $3 "Invaders Magazine" with color photos of invasive species can be ordered from the New England Wild Flower Society by calling 508-877-7630, ext. 3405, or you can learn more by visiting sive.htm. Click on the magazine cover icon near the top of the page to download "Invaders" as a PDF.

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