Pretty Perilous Plant

It's one of the only flashes of color left on the barren November landscape; the fiery orange berries of oriental bittersweet beckon passers by to just go ahead and snip a few vines for the barn door or the Thanksgiving table.  There are several spots in Concord where the vines grow within reach of one's garden shears - alongside roads and at the edges of fields.

Trouble is this is a prolific invasive species, and each one of those harmless-looking little berries, dressed in their pretty yellow jackets, is an ecological time bomb loaded with seeds that can germinate and spawn new plants. 

"My biggest fear is people moving this around," says Dr. Les Mehrhoff, Director of the Invasive Plant Atlas of New England.  "We move these things much, much farther than the natural dispersers – the birds, the wind, the water."

Oriental or Asiatic bittersweet (Celastrus orbiculatus) was brought to the U.S. from its native Asia in the late 1800s as an ornamental plant.  It has bright orange roots and thick clusters of berries that grow along its dark-brown, unruly vines.

Its indigenous counterpart, American Bittersweet (Celastrus scandens), has berries that grow at the tips of its stems, but it's so rare these days that it's become a protected species in some parts of the country.

Oriental bittersweet is a hardy species with vines that grow fast to as high as 60 feet and four inches thick, spiraling up the trunks of native trees to choke the forest canopy and outcompete shorter plants for sunlight.  It now grows so thick alongside some major highways in New England that it poses a safety risk to humans because big trees laden with heavy bittersweet vines can fall on passing traffic during ice storms or heavy winds.

To complicate matters oriental bittersweet is one of countless invasive species whose spread Massachusetts officials are fighting to control.  "New exotic species are coming into the state almost daily," says Scott Soares, the state's Agricultural Commissioner.  "With the limited resources the Commonwealth has our best opportunity is to get the word out about what they are, and hope that we can work in partnership with the public and remove those infestations."

But oriental bittersweet is extremely difficult, if not impossible to remove without herbicide treatments, and despite the state's outreach efforts there's still a troubling lack of public awareness about the plant's invasive properties. 

State law bars the importation, sale, trade, purchase or distribution or oriental bittersweet, but that hasn't stopped people from clipping the vines to make holiday wreaths and other decorations.

Plant biologists warn any unwitting culprits out there who might already have assembled this year's centerpiece that bittersweet should never be chucked in compost piles or disposed of with general yard waste.  Instead bittersweet decorations should be burned before they dry out and the berries start falling off.

Artificial alternatives might not be as pretty but at least they're lower maintenance and easier on the conscience.

More information: MassWildlife publishes a $5 "Guide To Invasive Plants in Massachusetts" containing invasive plant descriptions, photos, key identification characteristics and likely habitats.