Management of Black Locust at Tommy Thompson Park Cell 2 Wetland
As part of the Invasive Species Strategy, Toronto and Region Conservation Authority (TRCA) has inventoried and is starting to manage Black Locust, Russian and Autumn Olive trees at Tommy Thompson Park.
The invasion of these species, particularly Black Locust, is rapidly expanding and outcompeting native trees and shrubs throughout the park.
During spring 2022, management is focused on the Cell 2 wetland, which was constructed in 2016. There were a few clumps of Black Locust around the periphery of the construction zone, and they have since spread in alarming numbers, with more than 800 stems that are classified as “small” and 54 larger trees.
Black Locust is a tree in the pea family native to the Appalachian Mountains in the United States and was introduced to Ontario. It is fast growing, can survive in nutrient-poor soils, and can withstand many weather extremes. It spreads through seeds, and suckering (where many stems come from one root).
Its presence at Tommy Thompson Park is a problem because it forms dense colonies that shade out native plant species, including trees, shrubs, wildflowers, and grasses. This reduces biodiversity and impacts the investments in habitat restoration. Black Locust also has showy flowers that attract pollinators and can reduce pollination rates of native species.
As an Environmentally Significant Area, Tommy Thompson Park needs to be protected from invasive species.
Management includes cutting the trees and treating the stumps with Garlon RTU to prevent suckering and regrowth. Large logs are being relocated to the Peninsula B Double-crested Cormorant ground nesting colony. Here they will provide structure to promote ground nesting in areas where the 2017 and 2019 flooding washed away existing structure and have not since been occupied by ground nesting cormorants.
Small logs will be left on-site to decompose and add organic matter to the soil; however, some will be chipped, as there are too many to leave them all.
Management success will be monitored through 2022 and managed areas will be planted with native trees and shrubs in spring 2023 to restore biodiversity and habitat for wildlife. This will be a multi-year project, with management and restoration prioritized in areas where rapid invasive species expansion is observed.