Preventing plant invasions by using public gardens as sentinels

Background/Question/Methods - Invasive plants are a continuing problem in the United States and elsewhere, negatively impacting natural areas and landscapes. Many woody invasive species in the United States have a historical or present horticultural use. In order to effectively reduce the impacts of these species, they need to be identified as early as possible – preferably before any widespread commercial release occurs. One approach to prevent future invasions is to harness the expertise of public gardens. As institutions that plant and monitor non-native species of ornamental value, these institutions collect valuable data on plant growth, survival and reproduction over time. In addition, public gardens often maintain collections of different cultivars of given species, typically planted in close proximity to one another. Furthermore, many public gardens also maintain natural areas on their properties and have active management plans to eradicate invasive plant species. Thus, public gardens are well-situated to act as sentinels, by monitoring the behavior of non-native species in their collections. Since 2016, a working group of several North American Public Gardens and affiliated nonprofits have been working to create a communication network to share information about non-native plants that may be escaping from cultivation on their sites. As a proof-of-concept project, data on non-native plants classified as problematic by six different gardens were analyzed to determine how commonly the same species were found to be problematic across the gardens.

Results/Conclusions - In this presentation, we present the results of our analysis. Many of these species have already been removed from gardens’ collections because of invasive tendencies, while others are being carefully monitored for further spread. A total of 844 plant species and cultivars were identified as being problematic across all gardens, several of which have past or current ornamental use. For example, 10 species/cultivars were identified across 5 gardens, 17 species/cultivars across 4 gardens, 34 species/cultivars across 3 gardens, and 129 species/cultivars were identified across 2 gardens. This project indicates that public gardens have great potential to help prevent the introduction of invasive species in North America – especially as early sentinels to identify species that may later prove to be problematic - and therefore should be included in efforts to address plant invasions.