COS 133-5 - How we got here: Uncovering a consistent history of non-native plant sales across the U.S.

Background/Question/Methods

The ornamental plant trade introduces non-native plants to the lower 48 United States, of which some establish and become invasive. Invasive plant species have negative impacts on native ecosystems, economies, and human health. Studies of modern nurseries have revealed a strong reliance on non-native plants, but it is unclear if non-native plants have always been favored. By analyzing historical patterns of ornamental plant sales, we can assess historical proportions of non-native plants as well as turnover in nursery plant offerings over space and time. Understanding the historical ornamental plant trade can help to encourage practices that reduce invasions, including identifying a wide array of viable native plants. Here, we compiled and standardized a dataset of 38,985 unique catalogs in the Biodiversity Heritage Library’s (BHL) Seed and Nursery Catalog Collection to examine this history both spatially and temporally. Each record represents an individual species offered, at a specific time, sold at a specific nursery. We used these data to ask how the proportion of native versus non-native ornamental plant sales has changed over space and time historically. Additionally, we compiled a list of historically offered native plants for sale to inform the development of native plant stock today.

Results/Conclusions

We combined the BHL dataset with USDA Plants data to add unique species accepted names, codes, growth habit, and introduction status. Based on city names, we geolocated 98% of BHL records . The resulting dataset spanned 1725-2010, although most were concentrated between 1880-1940. Within this span there were over 1.4 million individual species offerings representing 9,293 unique taxa. 59.7% of the offerings were non-native species, 32.6% were native species, and 7.7% lacked a taxonomic resolution. Broken down by decade, the proportion of non-native offerings was relatively consistent (between 55.5% and 62.3%). Individual states varied in their proportions of non-native offerings (between 21% and 82% for states with >1000 offerings). Interestingly, 5,030 (54.1%) of the unique taxa were native versus 2,757 (29.7%) non-native (16.2% undefined). Thus, despite a higher number of native species available, non-native offerings were much more common.


Combined, these trends suggest little change in the ornamental plant trade’s attachment to non-native plants. However, as ‘growing native’ becomes increasingly popular, this work highlights thousands of native plant alternatives that were once sold across the U.S. By supporting efforts to break from historical patterns of ornamental plant sales, this work can ultimately reduce the introduction and propagation of invasive plants.