Public Gardens as Sentinels Against Invasive Plants

Due to their unique status as living museums of plants from around the world, public gardens and arboreta can play a unique and pro-active role in assessing which non-native plants exhibit invasive tendencies. These institutions have the access and staff expertise to observe the reproduction and spread (or lack there-of) of plants that are not well known and may not be available in the horticultural trade, and can make recommendations about these plants' capacity to become invasive based on those observations.

Over the last few years, MIPN staff and select Board members have been working to bring representatives of public gardens to come together and discuss how they can collaborative to address the issue of plants escaping from cultivation. We are continuing that work through a Public Gardens as Sentinels of Invasive Plants (PGSIP) working group, generously supported with funding from USDA-NIFA via the North Central Integrated Pest Management Center and the Richard King Mellon Foundation. Previous support has also been granted by the Stanley Smith Horticultural Trust. Institutions that participated in the launch of the PGSIP working group included: Holden Arboretum, Lady Bird Johnson Wildflower Center, Missouri Botanical Garden, Morton Arboretum, New York Botanical Garden, and Royal Botanical Gardens. They were later joined by the Chicago Botanic Garden.

An article about the project was published in 2019 in Public Garden, the Journal of the American Public Gardens Association (view pdf file here). In 2020, the PGSIP working group released a set of guidelines intended to help public garden staff easily list and rank plants escaping from cultivation in a standardized way based on their observations. This was followed by an online database to allow public gardens to upload and share their ranked lists. A 2022 "proof of concept" paper was published in Biodiversity and Conservation using plant lists from 7 public gardens that were generated prior to developing the new PGSIP guidelines. This study demonstrates how gardens have been paying attention to invasive species within their properties, but it also emphasizes the need for gardens to now work together and share their information.

Public garden and arboreta representatives can request log-in credentials to view existing data and contribute records to the PGSIP database. For more information, visit the PGSIP website


Plants on the Move attendees view an Amur Corktree (Phelloodendron amurense), a tree that escapes cultivation and is listed as invasive by certain Midwestern states.

In November of 2016, MIPN worked with The Morton Arboretum and the Ohio Invasive Plants Council to host an event called the Plants on the Move Summit. Representatives from 26 U.S. and Canadian public gardens attended to discuss how various institutions are currently addressing plants escaping and how the public garden community can better share and communicate observations of plants escaping cultivation with each other, with their visitors, and with the general public. A report summarizing the summit proceedings, discussions, and findings of this meeting is available (pdf). One of the primary findings of the summit was that the public garden community would benefit from some sort of shared data portal where gardens' staff could enter and share observations between institutions of plants escaping cultivation. This idea has formed the basis of the PGSIP working group's efforts over the last few years. 

It should be noted that PGSIP builds on a strong foundation previously built by others. In 2001, ecologists and horticulturalists representing multiple sectors gathered in St. Louis and developed a set of voluntary guidelines aimed at reducing the risk of invasive plant introduction and spread for several sectors, including public gardens. These guidelines are collectively known as the St. Louis Declaration. Many public gardens and arboreta have integrated the Declaration commitments into their strategic plans and operating procedures.