Invasive plants impact the environment, economy and human health of citizens of the United States. While many introductions are accidental, historically a significant number of plant species were introduced as ornamentals. This pathway has led to the establishment and spread of some highly invasive species including common and glossy buckthorns (Rhamnus cathartica and Frangula alnus), Callery pear (Pyrus calleryana), Japanese barberry (Berberis thunbergii), dame’s rocket (Hesperis matronalis), and water hyacinth (Eichhornia crassipes).
While the horticultural industry has recently become aware of this issue, many obstacles must be overcome to eliminate this pathway. To address this issue the Invasive Plants in Trade Working Group was formed with funding from the North Central Integrated Pest Management (IPM) Center. The overall goal of this working group is to develop strategies for reducing the sale of invasive ornamental plants in the North Central United States.
Past efforts of the working group have focused on raising awareness among the industry and helping participants to understand various state regulations aimed at controlling the “worst of the worst” invaders. Recently the working group explored a new question of whether sterile cultivars of invasive species, which retain their ornamental appeal but are not capable of producing viable offspring, might be a viable solution to the ornamental invasive problem. A survey conducted by the working group found that over 80% of industry representatives responding would promote sterile cultivars over their seedy counterparts meaning that this could be a viable alternative for both industry and be safe for the natural environment. The working group further explored how ecologically sound this approach truly is and whether or how sales of such cultivars should be regulated.
Invasive Plants in Trade Working Group’s discussion of sterile cultivars drew upon the perspectives and experience of a diverse group of stakeholders including plant breeders, propagators, researchers, regulators, and land managers. As a result of their discussion, stakeholders broadly agreed that this concept holds promise, but recommended that an agreed-upon terminology needs to be used when discussing sterile cultivars, and a regional testing program should be developed to provide unbiased data on the level of sterility exhibited by cultivars growing in different environmental settings. If these recommendations are implemented, this could potentially facilitate state regulation of sterile cultivars plants that would be both protective of natural resources and encouraging of innovative plant breeding and testing.
As an evolution of the Invasive Plants in Trade Working Group and building on its work to date, a new regional effort is being planned to further address woody ornamental invasive species (trees, shrubs, and woody vines) in the Great Lakes region. This work, funded by the U.S. Environmental Protection Agency (EPA) through the Great Lakes Restoration Initiative, will engage many of the same working group stakeholders to develop specific resources that can benefit all participants including a clearinghouse website for information specific to woody ornamental invasives of the region, improved decision-making tools for when to remove invasive ornamentals and how to replace them, improved outreach and education materials, and continued synthesis of technical information.