The City of Toronto maintains planted and naturalized areas through best management practices such as forest thinning, prescribed burns and controlling invasive plant species. Those practices create healthy forests that provide many environmental benefits. Learn how you can help and what to expect when forest management operations are happening in your area.
Pollution, construction, erosion and other factors deteriorate our natural habitats, and invasive species take advantage of the disturbance to thrive. Invasive species compete with native plants for growing space and nutrients. Please keep in mind that Invasive species management on public land is done by UF qualified staff only.
You may need a permit to Injure or Remove a Tree.
| Plant Type | Method: Manual Control | Method: Chemical Control |
|---|---|---|
| Herbaceous Annual or Biennial
(Garlic mustard, Himalayan balsam, tall sweet white clover, burdock) |
hand pull or cut close to the base when flowering | only in extreme circumstances |
| Herbaceous Perennial
(Dog-strangling vine periwinkles, Japanese knotweed, goutweed) |
|
apply herbicide using spray bottle or sponge:
|
| Woody
(Norway maple, Manitoba maple, white mulbery, Siberian elm, white poplar, common buckthorn, tartarian honeysuckle, burning bush, Asiatic bitterwseet, riverbank grape) |
|
cut stems and apply herbicide to stem |
Cosmetic use of pesticides is prohibited unless authorized by a permit from Ministry of Environment, Conservation and Parks.
A prescribed burn is a deliberately set and carefully controlled fire. It burns low to the ground and consumes dried leaves, small twigs and grass stems but does not harm larger trees. It encourages the growth of native savannah vegetation and sets back the growth of undesirable invasive species.
Prescribed burns are:
During prescribed burns:
Toronto is home to the rare black oak savannah ecosystem. Only 1% of this ecosystem remains after human settlement. This ecosystem can be found in High Park, Lambton Park and South Humber Park.
High Park contains about 23 hectares of fragmented black oak savannah and is the most significant area of the savannah ecosystem in Toronto.
Prior to European settlement, the landscape was defined by Indigenous Peoples’ use of controlled burns to manage the landscape, coupled with naturally-occurring wildfires. Indigenous people would use fire to clear the land for agriculture, to rejuvenate the quality and quantity of forage and medicinal plants, and to attract wildlife. This use of fire also helped to regenerate and maintain savannah habitats. Prescribed Burns are designed to echo these historic controlled and natural fires and benefit native plants and animals by reducing invasive/exotic plants and grass, stimulating native plant regeneration, restoring wildlife habitat and returning nutrients to the soil.
Tree thinning is a selective removal of trees and shrubs from a densely planted area so that the remaining trees will have better access to growing space, light, water and other nutrients.
During a tree thinning:
Sites may look different after tree thinning.
Succession is the natural process of replacement of one group of plants by another group of plants in an area over time. Species that are more tolerant to shade will naturally replace the species that are fast-growing and less shade tolerant.
Tree thinning mimics succession. In the City of Toronto, thinning will be implemented in the areas that were densely planted with a mix of sun and shade-loving trees. Short-lived, sun-loving trees such as poplars provided habitat for the growth of long living, shade-loving trees such as oaks and maples.
Once the long living species become well established, the short-living species are removed to reduce the competition for growing space and promote the growth of the shade-loving species.
The Ontario Ministry of Environment, Conservation and Parks Cosmetic Pesticide Ban limits the use of pesticides by homeowners for cosmetic uses. There are exceptions for forestry management, arboriculture, health and safety, and natural resource management. Application of pesticides under these exceptions will require the services of a licensed exterminator.
The City of Toronto uses herbicides under the natural resources management exception to manage larger areas infested by aggressive invasive species that can’t be managed manually.
The City of Toronto uses two Class 9 pesticides regulated by the Pesticides Act.
Roundup Weathermax is the primary herbicide used by the City. It is considered non-toxic.
Garlon RTU is used for species that don’t respond to Roundup Weathermax. It is particularly good for roots. This herbicide can also be used in colder weather. It has a low-toxicity.
Coloured dye is mixed with the herbicides to indicate where it has been used. City staff will post signs indicating the area that has been treated. Please follow the instructions on the signs until they have been removed.
Pesticide use is regulated. Any use of pesticides (including herbicides) is prohibited in the city of Toronto and homeowners shall focus on manual methods of invasive species management.