Urban Forest

What is it?

The Urban Forest is the full collection of trees and shrubs in a city, including those in parks, on streets, in ravines, and on private properties in front and backyards. These plants are an important part of managing stormwater flow by intercepting rain, absorbing water, and slowing runoff. Ideally, a city should maintain a tree canopy cover of 35 - 40 %, Toronto has coverage of approximately 20%.

How Does it Work?
The Tri Level Canopy is the collection of vegetated layers that catch, absorb and allow for evaporation as rain falls. The top layer includes the high tree canopies that intercept rain; this canopy holds back the majority of water. The middle canopy includes the hedges and shrubs under the trees, while grass or other groundcover that allows infiltration makes up the third level of the canopy. A tri-level canopy occurs naturally in forested areas, but needs to be recreated on residential lots.

Benefits of the Urban Forest

• Urban forests prevent runoff by intercepting rain in their canopy, on their bark, and later through infiltration.
• An increase in tree cover from about 25% to 50% on a residential lot can reduce runoff from about 10% to 20%.
• In addition to the filtering of rainwater through the soil, the roots of trees and other plants clean the water by assimilating, or absorbing, chemicals and heavy metals.
• Trees provide shade and lower surface temperatures on roads, walkways and other paved surfaces, reducing the heating of rainwater that runs across its surface. This minimizes the Fast, Hot and Dirty impact of runoff pollution.
• Trees help protect your house from rain, heat and wind, reducing your energy use. They also shade your lawn and garden, reducing their water needs in summer.

Important Facts:

• The City of Toronto maintains over 500,000 street trees on city property, and approved the Private Tree By-law to restrict the removal of trees on private property.
• The majority of large trees in Toronto were planted around 1920, these trees now have about 10 - 15 years left in their life expectancy.
• New urban street trees only have a life expectancy of approximately 5 years due to the stresses of urban life - confined soil space, polluted runoff, low nutrients, and compacted soil.

Costs:
Tree and shrub costs can vary drastically depending on age and size of tree and species. Trees can be grown from seedlings, and installed by the homeowner. Larger trees may need professional installation. See the Resources page for links to subsidized and free trees in Toronto.

Maintenance:

• Trees and shrubs need regular maintenance and care, especially in the first five years after planting. Maintenance includes watering, mulching and feeding younger trees, regular pruning, and inspection for diseases and pests. Much of the maintenance can be carried out by the homeowner, but professional arborists should be called in for pruning and disease/pest inspection and treatment.
• Water your street trees! During drought periods, water 2 minutes a day with a garden hose or with two 2 litre pails to ensure a healthy urban forest. Newly planted trees die from drought more than any other cause.
• Protect the roots of trees: don't pave too close to trees, and avoid compacting the soil under the tree canopy (don't park or store heavy items, like construction materials, under a tree).

Let's Plant More Trees!
To find resources on selecting the right species and location of tree for your property, and information about free or subsidized trees available to homeowners in Toronto, see the following Resources:

LEAF, (Local Enhancement and Appreciation for Trees) offers a subsidized backyard tree and shrub planting program, as well as workshops and information about tree care. Visit www.leaftoronto.org or call (416) 413-9244.

The City of Toronto Urban Forestry Services plants trees on City-owned street allowances fronting residential properties for free. Download the residential street tree brochure http://www.toronto.ca/trees/tree_planting.htm and call to see if you qualify for this service: (416) 338- TREE (8733).

Resources

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