What’s Growing at the Harriet Irving Botanical Gardens: Invasive Plants

Samuel Jean, Conservation and Education Assistant

I am writing these lines on the International Day for Biological Diversity and I hope that it will inspire landowners, and gardeners especially, to act on a threat to biodiversity: invasive plants.

Invasive plant pulling is part of the daily work at the Harriet Irving Botanical Gardens. Despite continuous monitoring, several plant species that are not native to the province and that are known to shade, crowd, and overwhelm native plants find their way into the Gardens. Unlike native plants, invasive plants did not evolve for thousands of years along with the wildlife that is present in our region. As a result, wildlife is not able to use these plants to their full potential. Native bees need native plants. The insects that most terrestrial birds depend on to feed their nestlings need native plants as well. On top of not sustaining wildlife, invasive plants are hard to manage due to their aggressive growth and can have negative impacts on economic sectors such as agriculture, forestry, fisheries, and tourism.

Invasive plants came here, and are still getting here, by various paths. Horticulture is one of them. Nowadays recognized as one of the worst invasive plants in the world, Japanese knotweed (Fallopia japonica) was once used as an ornamental plant. Once planted in your garden, an invasive plant is free to produce seeds that can be dispersed by the wind or by birds into natural areas, out of your sight, where they can germinate, grow, reproduce, and disturb the ecosystem. Cuttings and seeds from these plants can also disperse the species by floating down a stream or by hitchhiking to a new garden when you share plant divisions with other gardeners or forget to clean your shoes after hiking in an infested area.

At the Harriet Irving Botanical Gardens, we are currently using the 2019 Maine Advisory List of Invasive Plants (maine.gov/dacf/mnap/features/invasive_plants/invasives.htm) as a guide to determine which species we need to deal with. We encourage you to do some research about the plants that you currently have in your gardens and about the ones that you want to add to it. Remove or avoid the ones that are listed as invasive in nearby jurisdictions. The plants we choose to include in our gardens can have an impact, positive or negative, on the ecosystems that surround them, and we do have complete control over what grows in them. Let’s make our gardens as inviting as possible for wildlife by growing as many native plants as possible.

Keep an eye on our Facebook page over the next few weeks as we will be presenting the invasive plants that we are currently dealing with in the Gardens and other ones that are present in Nova Scotia. If you encounter these plants, feel free to submit your observations through the invasive and potentially invasive plants of Nova Scotia iNaturalist project. For more information about invasive species in Nova Scotia, visit the Nova Scotia Invasive Species Council website: nsinvasives.ca/

Photo (courtesy of Samuel Jean): Garlic mustard (Alliaria petiolata), an invasive plant that is present along the Acadia University Woodland Trails.