If you think the topic of invasive plants is a constant source of contention between environmentalists and members of the nursery/landscape professions, think again. Cooperation among conservation organizations and the nursery industry on the invasive-plant issue is natural and logical.

“It’s a win-win situation. Halting the sale of invasive species is good for the nursery’s bottom line as well as for the environment,” said Bill Brumback, New England Wild Flower Society conservation director. “Nurseries don’t want their plants to affect natural areas. No professional wants to sell a product with harmful side effects. On the other hand, they are right to say, ‘show me’ in asking for concrete evidence.”

Defining ‘invasive’ is a start

Brumback has firsthand experience with the positive effects of cooperative engagement on this issue. As a member of the Massachusetts Invasive Plant Advisory Group (MIPAG), a collaborative effort involving scientists, regulators, and professionals in the nursery/landscaping industry, he and his colleagues spent six years researching the evidence of plant invasions.

MIPAG’s first goal was to achieve a working definition of invasive plants:

“Non-native species that have spread into native or minimally managed plant systems in Massachusetts. These plants cause economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems. As defined here, ‘species’ includes all synonyms, subspecies, varieties, forms and cultivars of that species unless proven otherwise by a process of scientific evaluation.”

MIPAG substantiated invasiveness through scientific investigation, including peer-reviewed papers, herbarium specimens and published data. A plant’s reputation as a garden thug or an opportunist in highly disturbed areas like roadsides was not enough to warrant the invasive label.

Three categories were established: Invasive, Likely Invasive and Potentially Invasive. Each species studied had to meet criteria to be placed in one of them.

The biology of invasiveness

MIPAG’s definition of invasiveness focused on an exotic plant’s domination of minimally managed areas. These sites, sometimes referred to as “natural areas,” are often maintained infrequently at best, with a minimum expenditure of labor and resources.

Yet they are preserved because of their biodiversity, critical habitats or important plant communities. Because of their minimal maintenance, an invasive plant’s progress of infestation is readily apparent, and due to their environmental value, it is especially problematic.

Non-native invasive species are the ultimate survivors of the plant world. They establish readily in a variety of habitats, grow quickly, are largely free of pests and diseases and reproduce efficiently through vegetative means and/or copious production of well-distributed seed.

They do all of this so well they dominate the areas they colonize. Even those who have little interest in plants and gardening can recall a wetlands’ late-summer sea of purple loosestrife, the autumn mantles of Oriental bittersweet suffocating trees, or the impenetrable mats of kudzu -- often called “the plant that ate the South.”

The characteristics that make a plant an Olympic-caliber competitor are sometimes the same ones that make it highly desirable as a cultivated plant. Beautiful, hardy and resilient, these sure-bet species can be much in demand by gardeners, landscapers and state agencies set on enhancing outdoor spaces.

MIPAG’s conclusions

Of the many plant species growing in New England, one-third are not native. Of these, fewer than 100 have an effect on natural areas. In Massachusetts, invasives sold in the nursery trade number no more than two dozen. However, some of these are sold in great numbers, making them especially problematic.

After a 6-year study, MIPAG concluded that sufficient data existed to list 33 species as Invasive, 29 as Likely Invasive and four as Potentially Invasive.

Nineteen plants did not meet the criteria for listing in any of the categories, although many are species of concern that warrant further investigation. Of the 66 plants that met criteria of invasiveness, 14 were being sold in the nursery trade, including such popular species as Norway maple (Acer platanoides), Japanese barberry (Berberis thunbergii) and burning bush (Euonymus alata).

MIPAG’s final report in February 2005 included principles for managing invasive species as well as priorities for education and research.

Massachusetts list

The Massachusetts Department of Agricultural Resources took MIPAG’s system of collaborative environmental responsibility to the next level. It created the Massachusetts Prohibited Plant List, which went into effect Jan. 1, 2006.

Importation of any of the 66 MIPAG-listed plants was banned after a specified date. For the 14 plants in the nursery trade, the department established one- and three-year propagation ban phase-out dates. These phase-outs were allowed only on plants that entered the state before the importation ban date.

After that date, the sale, trade, purchase, distribution and related activities for that plant are prohibited.

The ruling was done in cooperation with the nursery industry. It represented an excellent compromise between enforcing an immediate ban (to the detriment of the trade) and continuing to allow these plants to be sold (to the detriment of the environment).

Massachusetts nurseries had a reasonable length of time to sell stocks of banned species and to plan a transition away from these popular plants.

While regulation seems much more severe than a voluntary system, it levels the playing field. No Massachusetts nursery can be disadvantaged by being an environmentally responsible purveyor who does not offer invasive plants to consumers.

The win-win

Instead of focusing on the loss of certain popular plants, think about the benefits of this paradigm shift in gardening.

“Educating the consumer about invasives and promoting alternatives is a tremendous marketing opportunity for the industry,” said Greg Lowenberg, New England Wild Flower Society education director. “It allows nursery professionals to be seen as environmentally responsible, progressive and green. Giving accurate information about a product creates an informed buyer. And an informed buyer is a faithful buyer.”

Steering consumers away from the old tried-and-true species opens up a new palette of plants to promote. The industry has the skills and the knowledge score a win-win on this issue. And the professionals who are good educators and marketers are the ones who will reap the biggest benefits of a post-invasive era in the trade.

-Gail Kahn

 

Gail Kahn is a guide, New England Wild Flower Society, (508) 877-7630; www.newenglandwild.org. 

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