Invasive Plant Species at RBG and the Fight to Protect Biodiversity

By Tys Theijsmeijer, Senior Director of Ecosystem Stewardship Programs and Policy

Invasive species are simply defined as any living organism—a worm (such as the Hammerhead Worm), plant, insect, fish, fungus, bacterium, or even an organism’s seeds or eggs—that is not native to an ecosystem and causes harm. They represent one of the most significant and growing threats to ecological systems worldwide, particularly in our local natural areas.

Royal Botanical Gardens’ (RBG) natural areas sit at the western end of Lake Ontario, adjacent to a shipping port, a rail corridor, and a major highway. In the 1800s, the original shipping port was located within the Cootes Paradise property. These transportation and trade hubs are among the primary pathways for the accidental introduction of invasive species, as they facilitate the movement of goods and people across regions and continents. Currently, more than 300 species of Eurasian plants have successfully colonized RBG’s natural areas, along with a growing number of other invasive species, the most recent being the Hemlock Woolly Adelgid.

Additionally, botanical gardens have traditionally played a role in the global trade of plants and, as a result, have been a source of invasive plants and insects. However, modern botanical gardens have updated their practices and now work together to prevent the introduction of invasive species while also raising awareness of local threats. In our region, some of the most problematic invasive plants that have spread into natural areas from RBG’s historical plant collections include Tartarian Honeysuckle, Amur Honeysuckle, Amur Cork Tree, and an RBG-specific hybrid Magnolia. Over decades, these species have accumulated to more than one million individual plants across RBG’s 400 hectares of forested areas, with honeysuckle being the most dominant. Many other invasive species are present and abundant, including Common Privet, Common Buckthorn, and Multiflora Rose.

For more than a decade, RBG has been working to mitigate the spread of invasive species both within its gardens and across its natural areas. On-site efforts have successfully eliminated hundreds of patches of Common Reed (Phragmites australis) from the marsh. Recently, RBG crossed the milestone of removing over 500,000 woody invasive plants—such as honeysuckle—from the forest, often with aid from RBG’s volunteers. However, with another 500,000 still to go, plus the next generation of seedlings, the work is far from over— and that’s just within RBG’s site.

Learn more about RBG’s plant communities in our environmental status reports, available on our Forest Conservation webpage under “Resources”. Additional resources, including a one-page action plan for gardeners, can be found through the Ontario Invasive Species Centre. Beyond these sources, the internet offers a wealth of growing information on invasive species, helping us all gain a clearer understanding of the threats they pose to our natural environment.