An economic analysis of the invasive plant problem associated with the horticulture industry in North America

The growth in demand for nursery products by consumers has led to the expansion of the global horticultural industry. However, this expansion has also increased the risk of accidental introduction of harmful nonnative species in host ecosystems. Commercial horticultural activities, especially increased imports of exotic plant material and expansion of nursery operations, have become a significant pathway for invasive species to invade natural environments in many regions of the world (Maki and Galatowitsch 2004). Reichard and White (2001) cite research suggesting between 57% and 65% of the naturalized flora in Australia were intentionally introduced via horticulture and argue that the percentage is even higher for woody species introduced to North America. There is a correlation between the number of plants introduced and the probability of invasion, a phenomenon called “propagule pressure.” For instance, an analysis of catalogs from several nurseries in Britain found that the frequency of sale in the nineteenth century predicted naturalization today (Dehnen-Schmutz et al. 2007a). Another study found that the species whose seeds were sold then at lower prices were more likely to be invasive now, suggesting that they may have been purchased more often because they were less