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 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.

The Public Gardens as Sentinels against Invasive Plants (PGSIP) initiative brings together public garden representatives to collaboratively identify and address plants escaping from cultivation. PGSIP is guided by a working group led by The Morton Arboretum along with MIPN, Missouri Botanical Garden, Royal Botanical Gardens, Chicago Botanic Garden and other key partners.


PGSIP Data & Resources

As of October 2023, 29 public gardens and arboreta across North America have shared observations of plants escaping cultivation, contributing to a database with over 850 plants records. These contributions have enabled PGSIP to begin issuing Plant Alerts designed to raise awareness of ornamental plants that have been reported by participating gardens and to provide recommended actions to prevent their introduction and spread into the wider landscape. While database access is restricted to participating gardens, we have a new publicly available data dashboard that showcases plants most commonly reported by public gardens. There is an option to filter the data by state or region. 

Sign up here to receive Plant Alerts

Access the PGSIP Data Dashboard


The History of PGSIP

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 garden staff being able to share observations between institutions of plants escaping cultivation.

A PGSIP working group was formed in 2018 to develop a framework whereby gardens could share these types of observations. 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. Rankings including Watchlist, Potentially Invasive, Invasive and Assessed as Invasive. Development of the Guidelines was followed by creation of an online database that allows 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 emphasized the need for gardens to work together and share their information.



All North American public gardens and arboreta and invited and encouraged to participate in PGSIP. Garden representatives can request log-in credentials to view existing data and contribute records to the PGSIP database. For more information, visit the PGSIP website

PGSIP is 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.


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.


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.