September 15, 2010
Group sees invasive plants compete with natives
Those taking part in the tour of parks and conservation areas see first-hand the damage caused by invasive plants.
In the spring of 2009, members of the horticulture industry and the conservation community came together to discuss shared concerns and take co-operative action to manage invasive plants and protect native vegetation.

This group of people with diverse, yet overlapping, experiences, interests and concerns came to be known as the Horticulture Outreach Collaborative. Earlier this year, the group officially became a committee of the Ontario Invasive Plant Council.

The collaborative hosted a free tour in late July, entitled, Garden Plants in Natural Areas, Parks and Ravines. Visiting native plant areas, members saw first-hand the damage caused by invasive plants. They also heard about methods to manage the effect of the plants, and to connect and network with others in the horticulture community.

The tour visited Rattray Marsh in Mississauga, where Vinca minor (periwinkle) had crept over 300 feet from a neighbouring backyard into the conservation area. The marsh is also experiencing invasions of Tartarian honeysuckle, Norway maple, black alder, rough manna grass, English ivy and privet.

At High Park, almost the same plants had spread into the natural areas: Tartarian honeysuckle, Norway maple, multiflora rosa, Asiatic bittersweet, euonymous, goutweed and periwinkle. It was felt that those infestations were likely caused from seeds dropped by birds, or carried by wind and water, from nearby gardens. A theory among some in attendance was that suppliers may substitute one cultivar for another of the same species, thinking it renders the same growing results, when it may not.

These sites demonstrated how certain garden plants move into natural areas, and compete with regionally-significant native plant communities. Discussions were lively, and much was learned by all. At the conclusion of the tour, it seemed a consensus was reached that some non-native plants might be useful in location-specific ways. It was also felt that a proper education program on the use of native and non-native plants would be helpful to reduce this kind of problem in the future.

Groups participating included Toronto Parks, Forestry and Recreation, Credit River Conservation Authority, Ontario Invasive Plant Council, commercial plant propagators/growers, and OMAFRA staff.

The collaborative consists of representatives from conservation authorities, government bodies, not-for-profit organizations, trade associations, businesses and academia. Founding and supporting members include Credit Valley Conservation (CVC), Landscape Ontario, Ontario Ministry of Natural Resources, Ontario Federation of Anglers and Hunters, Ontario Invasive Plant Council (OIPC), Ontario Streams, Sheridan Nurseries, and Toronto and Region Conservation Authority (TRCA). To see the website, go to