Population Control: Developing Non-Invasive Nursery Crops©

INTRODUCTION There has been considerable debate over the impact of invasive exotic plants and the best approach to address this problem. The problem, briefl y, is that some nonnative plants are weedy to the point of being invasive, i.e., they naturalize over large areas, displace native plants, and disrupt natural ecosystems (Westbrook, 1998). There are many examples of exotic plants that fi t this category. Ligustrum sinense (Chinese privet) has displaced the native shrub layer in 1 million ha (2.4 million acres) in the Southern United States. Cytisus scoparius (Scotch broom) has invaded 404,700 ha (1 million acres) in Oregon alone. The nursery industry has been a signifi cant contributor of invasive plants. Of 235 invasive woody plants in North America, it has been estimated that 85% were introduced for ornamental and landscape purposes (Reichard and Hamilton, 1997). Some of these species are still being produced and sold. Concern and awareness over the threat of invasive plants has been growing. In 1999, President Clinton issued Executive Order 13112 () calling upon federal cabinet agencies to coordinate their efforts to combat invasive alien species and established the National Invasive Species Council (), which, in turn, developed the National Invasive Species Management Plan () in 2001. Most states have since formed exotic plant pest councils () and many agencies, organizations, and individuals have developed and distributed “black lists” of plants that they feel should not be grown. Many of these lists include plants that are actively being grown by the nursery industry. The Connecticut legislature recently passed Public Act 04-203 () prohibiting the importing, moving, selling, purchasing, transplanting, cultivating, or distributing of 81 different plants with penalties of up to $100 per individual plant. The Commissioner of Agriculture in New Hampshire recently adopted an Invasive Species Rule (3800) prohibiting the collection, transportation, selling, distribution, propagation, and transplanting of 21 plants () with a number of economically important nursery crops [e.g., Acer platanoides (Norway maple), Berberis thunbergii (Japanese barberry), and Euonymus alatus (winged euonymus)] being included. Most likely, other states will follow suit.