FRAMINGHAM -- No one said invading hordes had to be ugly. Many people like to use the perky orange and yellow berries of Oriental bittersweet in holiday decorations. Burning bush foliage blazes red in the fall. And a sea of brilliant purple loosestrife can sure look pretty.
But invaders they are nevertheless. By the millions, Oriental bittersweet bines are clambering 60 feet up trees, swallowing entire forest stands. The seeds of burning bush start out in gardens but are soon spread by birds through woods and fields, where they choke out native vegetation. And purple loosestrife is strangling waterways while crowding out wildlife and native plants.
Last weekend, several hundred scientists, land managers, environmentalists, and volunteers convened for the second New England Invasive Plants Summit to share research on the plants, which a state-based advisory group defines as ''non-native species that have spread into native or minimally managed plant systems" causing ''economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems."
Most invasive plants are weeds, but some of the worst offenders are ornamentals sold at local garden centers, though that's changing in New England. The state Department of Agriculture has proposed a ban on importation of invasive trees, shrubs, and plants into the state as of Jan. 1. Some species would still be sold up to three years after the deadline to allow nurseries holding stock to avoid economic loss. Existing plantings would not be affected, so you wouldn't have to dig out your burning bush -- though it would be a good thing to do if you live near a natural area.
Common ornamentals on the Massachusetts list include all cultivars of Norway maple, bishop's gout weed, Japanese barberry, burning bush, yellow flag iris (Iris pseudacorus), purple loosestrife (lythrum), sycamore maple, garlic mustard, Japanese barberry, Oriental bittersweet, autumn olive, European buckthorn, dame's rocket, creeping jenny, variable water-milfoil, reed canary grass, Japanese honeysuckle, and the shrublike honeysuckles Lornicera morrowii, L. x bella, L. Maackii, L. japonica and L. tartarica. A complete list of the proposed banned plants is at mass.gov/agr.
New Hampshire is even further down the path of outlawing the invaders. Its Department of Agriculture began its ban June 1, 2004, with sale of Norway maple, burning bush, and Japanese barberry to be barred by 2007. Increasing evidence supports New Hampshire's ban on all cultivars of an invasive species. Supposedly sterile garden cultivars of purple loosestrife has been proven to produce invasive seeds and Jonathan Lehrer of the University of Connecticut, one of the conference sponsors, presented a study that found Japanese barberry cultivars such as the popular Crimson Pygmy can similarly produce seedlings that revert to the more invasive green form.
The New Hampshire ban is working ''great," said Douglas Cygan, invasive species coordinator for the state's Department of Agriculture. When he recently found
Among other New England states, Vermont has a quarantine list; so does Connecticut. Maine has a list of banned aquatic plants. And Rhode Island has a list of invasives, although without regulatory status.
All this activity would seem to be justified. A recent study of 81 rare plants in New England found that invasive species threaten 37 percent of their populations. Almost half (42 percent) of species on the federal endangered species list are in trouble due partly or totally to invasive species. Federal agencies spent $1.2 billion on invasive species (including new insect pests and plant diseases) last year and 13 bills before Congress address the issue, said Chris Dionigi of the National Invasive Species Council in Washington, D.C.
However, some horticulturists think that the presence of alien invasive plants in the ecosystem is inevitable. ''What's driving all of this is disturbance in the environment," said Peter Del Tredici of the Arnold Arboretum of Harvard University. ''Acid rain, global warming, exotic pests, and diseases are causing cracks in the ecosystem where invasives can outcompete the native vegetation, which may have been better adapted to the environment of 400 years ago, but maybe not today. I wouldn't bet against natural selection."
And the same non-native plants that can threaten natural areas are sometimes the only ones tough enough to survive pollution and road salt in urban environments. Even a wretched invasive such as phragmites, which grows 14 feet in solid stands, altering coastal wildlife habitats, can serve a purpose when it helps mitigate pollution in wetlands that are too toxic for many native plants.
But a real area of concern is when invasive species are planted by homeowners living near wild spaces. ''We're really worried about infesting minimally managed natural areas," said Bill Brumback of the New England Wild Flower Society.
''We want to promote native alternatives" to invasive ornamentals, said Gwen Stauffer, the new executive director of the society, which suggests substitutes on its website, newfs.org. ''We see the uses of non-native plants that are not invasive" for street and garden use.
The summit was presented by the New England Invasive Plant Group and the Invasive Plant Atlas of New England. The society, a cosponsor, has trained more than 500 volunteers to aid the atlas at the University of Connecticut with its project to collect data on up to 100 invasive plants. ''We have a very effective volunteer program throughout New England. We're doing all the states. It's incredible grunt work clearing wetlands of phragmites and lythrum. We have volunteers in canoes pulling out water chestnuts. One volunteer rappelled down a cliff to pull Japanese honeysuckle that was threatening a rare fern.
''We've been asked to do a presentation at the Botanical Gardens Congress International in China in 2007 so our program could be a model for other nations because we can mobilize so many grass-roots volunteers to do the work," said Stauffer.
''We're just learning a lot. The science is really new," said Ann Gibbs, state horticulturist with the Maine Department of Agriculture, of the conference reports. ''It looks like some of these plants can even change the soil chemistry so native plants can't compete as well."
To review a summary list of the invasive plants of the New England region, or to review the Massachusetts list and those of other New England States, visit ipane.org. To volunteer for the wild flower society's training and conservation work for critical natural areas throughout New England, contact Chris Mattrick at firstname.lastname@example.org.