Have you ever wondered about which invasive plant species dwell within the Hamilton landscape? Check out our blog below to learn more about invasives and their common characteristics. Free reference guide included!
Introduction to Invasive Plants
Introduction to Invasive Plants
Morrow Honeysuckle, as pictured, is one of four invasive honeysuckles out of sixteen that are native to Ontario. These shrubs tend to spread as dense thickets.
An invasive species is a species that has been introduced to a new region, characterized by new flora and fauna communities, yet it can survive in these new conditions due to being in a similar climate. These plants have not been in the region for long enough to have natural competition to control their population, and have adaptations that allow it to spread, reproduce and dominate an area quickly, especially if the geological and biological conditions are favourable for their establishment. Consequently, this displaces native species of wildlife, which in turn harms the food web, and as a result, reduces biodiversity as a whole. For example, according to research at Utah State University, berries native to North America are better for birds than berries produced by invasive species, due to being higher in fats and nutritional content.
An invasive Himalayan Balsam stem. If its pink, tubular flowers are not available to aid in this plant’s identification, distinguish it from native Jewelweed by the sharper, more serrated margins on its leaves.
A weed is an undesired plant in a specific area, often including invasive species, which colonize a landscape and establish itself faster than other plants. It outcompetes other species so that they are the only plant that can grow in the area. A good example of a weed would be dandelions, this naturalized plant is often unwanted in gardens due to its aggressive spreading nature, however, it is a good source of food for pollinators.
Winged euonymus, also known as burning bush for its vibrant autumn display, is stunning but invasive. Although it isn’t as aggressive as other woody species, its deep roots network allows it to survive droughts and establish quickly.
Characteristics of an invasive plant include long, strong roots. When they go deep into the ground, it is called a taproot. Various invasive species also have rhizomes; stems that creep along or just below the ground surface to send out new roots and shoots. These characteristics make them highly resilient, so pruning back rhizomes or not removing the entire root network will only delay their growth, it won’t kill them. Some species can even survive in yard waste bags if left intact!
Furthermore, other tricks of theirs include reducing another species’ ability to establish itself within the same tract of soil, utilizing techniques such as shading over the ground, changing the pH of the soil, depriving it of nutrients or altering the chemical composition of the soil. By releasing compounds such as alkaloids and phenolic acids, they can effect another plant’s ability to uptake nutrients. This relationship between the invasive plants and how they negatively affect the soil and other plants is called allelopathy.
Invasive Japanese Knotweed shoots can be cooked and eaten when they are harvested young. The mature stalks are strong and hollow, form dense colonies, and can reach up to 5 meters in height.
By now you are most likely motivated to take down the invaders of our urban and naturalized spaces - but which species are these? On behalf of Green Venture, we have created an identification booklet of the common invasive weeds in Hamilton for you to use at your leisure, take a look at the PDF attached below!
Common Invasive Plants in Hamilton
Now, all you have to do is get out there, pull those invasives out from the ground, and help save our outdoor spaces, one invasive plant removed at a time.
By removing invasive plants and weeds, we can restore native tall-grass prairie, which features forbs and graminoids with shoots up to 2.5 meters tall, and roots that grow down to 4.5 meters below the surface.
References:
Invasive Species Centre. (2025). Invasive Plants. Retrieved from Invasive Species Centre: https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-plants/
Ontario Invasive Plant Council. (2025). Species. Retrieved from Ontario Invasive Plant Council: https://www.ontarioinvasiveplants.ca/invasive-plants/species/
Runwal, P. (2020, June 12). Migratory Birds Like Native Berries Best. Retrieved from Audubon: https://www.audubon.org/news/migratory-birds-native-berries-best
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