Urban Forestry Projects

Ash Management

Ash Management

A row of Ash trees in various stages of decline in a City of Toronto park.

Dead and dying ash trees are being removed from natural areas due to Emerald Ash Borer (EAB) infestation. Dead ash trees along trails or close to other park infrastructure and adjacent to private property boundaries are a priority for removal due to public safety risk.

Survey work began in 2012 to identify priority sites for management.  Learn more about 2015 ash management plans and work completed in 2014.

All management sites will be reviewed to develop replanting plans and invasive plant control strategies as required to ensure successful tree replacement.

Frequently Asked Questions

Ash Tree Removal

Why were ash trees being removed from natural areas?

Dead and dying ash trees were removed from natural areas due to Emerald Ash Borer (EAB) infestation. Dead ash trees along trails or close to other park infrastructure and adjacent to private property boundaries were prioritized for removal due to hazardous condition. Ash trees within forests, away from public use areas, will be left to decline naturally to create habitat and to provide other benefits for wildlife. Dead trees will only be removed in these areas if the volume of debris impedes natural regeneration.

How are the tree removal operations being timed to reduce site impacts?

To reduce the impact on forest soils and vegetation,tree removal is taking place during the cold winter months when the ground is frozen and snow covered. Harvesting should not take place during wet spring weather, or during wildlife breeding/nesting season because the damage to the soil, plants and wildlife can be extensive.

What measures are being taken to protect wildlife habitat during tree removal operations?

In addition to the need to conduct tree removal operations during frozen ground conditions, operations are also being timed to avoid disturbance during the core nesting/breeding period from May 1 to July 31, supported by research from Environment Canada.

Protection of wildlife habitat, including wildlife tree retention, is a key consideration during site assessment to determine required tree removals. Especially considering the ecological status of some sites such as Guild Park and Gardens as an Environmentally Significant Area and South Marine Park, which is part of the provincially significant Scarborough Bluffs Sequence Area of Natural and Scientific Interest.

Can the public use sites while ash removals are on-going?

No. Temporary trail closures are required while tree removal operations are being performed and during the final stages of site clean-up for the safety of the public. Signs are being updated to identify dates of closure. The public should adhere to signage posted on site for their own safety and the safety of the forestry workers.

What is going to happen with the ash wood removed from the sites?

The wood removed will be disposed of at Urban Forestry’s wood disposal locations and processed into chips for eventual utilization as mulch. Some wood will be left on-site for use as wildlife habitat structures in naturalization areas.  Additionally, some wood may be re-purposed elsewhere for alternative uses.

Invasive Species Management

Why is pesticide being used in City parks?

The City of Toronto's natural area management program involves active removal of invasive plant species in Toronto parks to protect and restore existing native plant communities. Manual methods are used wherever possible or in combination with pesticide, to control invasive plants. The use of pesticide is required for the more aggressive plant species that have been proven not to respond to manual control efforts, or if manual efforts would result in unacceptable environmental damage. Invasive plants that are of particular concern in ash dominant sites include non-native shrubs like common buckthorn and perennials like dog-strangling vine.

What pesticides are being used? Are they harmful to people or pets?

The herbicide product Roundup Weathermax (active ingredient glyphosate), is used by Urban Forestry staff as the primary herbicide to control aggressive invasive species including dog-strangling vine, Norway maple, Manitoba maple, non-native Euonymous, and non-native honeysuckle species. Extensive scientific testing, by both the manufacturer and independent laboratories, indicate that glyphosate has a very low toxicity to wildlife and fish, and does not cause cancer, birth defects or nerve damage. It is therefore considered to be non-toxic. Glyphosate has a low vapour pressure; therefore it is extremely unlikely that applicators or bystanders will breathe in any vapours.

The herbicide product Garlon RTU (active ingredient triclopyr) is used for species that have proven not to respond to the application of Roundup Weathermax, mainly due to extensive root systems, such as buckthorn species, Siberian elm, tree of heaven and locust species. This herbicide can also be used in colder weather and during the plant dormancy season when Roundup is not as effective. Animal metabolism studies have shown that the active incredient triclopyr does not bio-accumulate in body tissues. If ingested, triclopyr is rapidly excreted unchanged, primarily in the urine. Oral toxicity is low, and long-term testing has produced no evidence that triclpoyr causes carcinogenic, mutagenic or teratogenic effects in mammals. Prolonged exposure to skin may result in minor skin irritation and redness. City staff wear protective clothing to reduce their exposure to these products.

How are pesticides being applied?

Licensed City staff or contractors are applying herbicide to the bark or cut stump of the invasive tree or shrub. Coloured dye is added to the herbicide to indicate where herbicide has been used. The pesticide will absorb into the plant's root system and slowly kill the species over time. Where there are very large colonies or conversely where there is a sparse population of shrubs, stems are being left in place and treated with the herbicide as a bark application with a paintbrush or sprayer in a circle around the base of the stem.

Throughout the following field season, during summer and fall of 2014, additional treatment may be prescribed for the ash management sites to reduce spread of invasive plants and competition to existing regeneration and new plantings. Information signs are posted along with the standard signage that alerts park users.

Why are invasive plants being removed from the ash management sites?

Some invasive plant species are being removed to control further spread that will occur when the ash canopy is gone. Increased light conditions and potential increase in site disturbance due to loss of trees will benefit many invasive species and allow increased seed production, growth and vigour. Removing them now will help to prevent their populations from becoming unmanageable, and also create space and increase success of re-planting efforts of native trees and shrubs. We realize that we cannot control all invasive species at Guildwood Park but will identify target areas and species to avoid the greatest negative impact from their spread.

How will the public know when pesticides are being applied?

In accordance with Provincial Ministry of Environment regulations, all areas to be treated with herbicide will be posted with an advisory sign surrounding the perimeter of treated areas. The signs are marked with the posted date and each treatment date. The signs are posted 24 hours in advance of the treatment and will remain at the treatment area for 48 hours following treatment as required by the Pesticide Act. The signs indicate which species are being treated and which pesticide product is being applied.

The public should stay on designated trails, follow site signage and keep pets on a leash and out of the treatment areas until the signs have been removed.

Forest and Site Restoration

What will the site look like after removals are completed?

Residents should be prepared for some sites to look drastically different depending on the number of trees that need to be removed. A variety of forest responses could be expected including: temporary ash stump re-sprouting, wind throw and tree tip-ups, sucker growth, and invasive plant species expansion. Longer-term monitoring will be required to follow site succession to ensure appropriate management is undertaken so native species will thrive in these areas.

Replanting strategies and invasive plant species control plans are being developed for these sites to replace ash trees and sustain healthy forest cover.

Replanting strategies and invasive plant species control plans are being developed for these sites to replace ash trees and sustain healthy forest cover.

What kind of trees will be planted to replace ash?

The most dominant ash species found in Toronto include white and green ash. Black ash is rare in Toronto, but is found in Guild Park and Garden. White ash and green ash grow in different habitat conditions: white ash prefers upland areas, while green ash tends to grow in moist lowland conditions.

In natural areas, a diversity of species appropriate to habitat conditions will be chosen to replace ash trees. Planting a high diversity of species will increase the resiliency of the forest as a whole and it's ability to deal with the introduction of future threats. Tree species appropriate to replace green ash include American basswood, Eastern hemlock, hackberry, white elm, silver maple, red maple, bur oak, Eastern white cedar, Eastern cottonwood, black maple, yellow birch and blue beech. Tree species to replace white ash include sugar maple, white birch, American beech, red oak, ironwood, black cherry, white oak, bitternut or shagbark hickory or white pine. A mix of native shrubs and wildflowers will also be planted in canopy gaps created by loss of ash trees to maintain native cover and compete with invasive species.

The City has partnered with Forest Ontario (formerly Trees Ontario) in the Tree Seed Diversity Project. This project collects and grows trees from seed collected in Toronto, including several species that are appropriate to replant ash dominant forests. These have included bur oak, silver maple, Eastern cottonwood, sugar maple, red oak and black maple.

When will planting occur at sites where tree removal is completed during this winter?

Tree planting will occur at all of the park sites where tree removal is taking place, starting in spring 2015. Initial planting will be prioritized in larger canopy gaps created by removal of ash trees. Trees removed from manicured areas within these parks will also be reviewed for replacement. Sites will be planted by City staff, and supplemented by contractors in order to expedite tree replacement. Some of the sites may require longer-term management to reduce competition from invasive species. Additional infill plantings could be expected in fall 2015 and spring 2016. More details and planting maps can be found here.

How will site damage incurred during tree removal operations be restored?

Urban Forestry does not plan to maintain any site access trails in the long-term, however temporary access using some of these routes may be required to replant and maintain new plantings. Many trails will disappear into the site landscape through re-growth of ground vegetation and re-sprouting of woody stumps. Where this does not occur, plantings will be established on these trails to fill in over time.

Will wood debris remain throughout natural areas?

Main pathways will be cleared of debris to maintain recreational use, however most of the brush and debris from tree removal work will remain throughout the natural areas to contribute to forest health and wildlife habitat. Although the material looks "messy", it will weather and become less obvious once the site fills in with new plantings. In some concentrated areas or areas that already have abundant debris from previous management, brush will be removed and/or chipped to increase opportunities for replanting.