Invasive plants are one of the leading drivers of native biodiversity loss with negative impacts at the species, community, and ecosystem level. The majority of invasive plant species in the United States were originally introduced as ornamentals. Once discovered to be invasive, many of these species became regulated by Federal and state governments to prevent further sales. However, it is unclear whether or not listing a species as invasive curtails its sale as an ornamental. We investigated the distribution of invasive plants for sale in the United States to identify 1) the proportion of currently known invasive plants that remain active in ornamental trade and 2) where these sales occur, particularly in violation of Federal and state regulations. We used standardized internet searches in Google and a database of nursery catalogs (Plant Information Online through University of Minnesota) to search for sales of 1285 plant species listed as problematic by the federal government, state government invasive plant, noxious weed, and noxious seed laws, and the Invasive Plant Atlas (https://www.invasiveplantatlas.org/).
Results/Conclusions
We compiled a database of more than 15,000 records of invasive plant sales across all lower 48 United States. Of the 1285 invasive species we searched, we found 61% for sale by either commercial nurseries (n = 1081) or online plant traders (n = 281), with eBay as the single greatest carrier of invasive plants. Of the species we found for sale, 343 were on state or Federal regulatory lists (50% of the 688 regulated species). We documented 5500 cases of regulated plant sales, including 382 cases in which species were sold in the same state where they were listed for regulation. We also found 20 of the 98 Federal noxious weeds for sale across 30 states. Clearly, the sale of invasive plants in the U.S. is ongoing despite their known negative impacts and regulations prohibiting their sale. States likely need greater support to enforce regulations, although the growth of online marketplaces and differing regulations among neighboring states challenges effective policy enforcement and prevention of invasions by the ornamental pathway. Better communication and outreach to growers and consumers across state borders is needed to reduce the sale of invasive plants.