Trees

This program focuses on replacing boulevard trees in the spring and fall seasons.

You may notice markings or flags around the boulevard once a locate request is submitted. The stump removal and/or tree planting will occur shortly after, and the boulevard area will be restored.

Spring Planting and stump removal will usually begin in May until early summer. Fall planting and stump removal begins in early fall through to December. The timing of your City tree removal will dictate if your tree is replaced in spring or fall.

Please Note: If you are unsure if you are on the planting list, or want to request a new tree, please contact Service Oshawa

This program focuses on large-caliper park tree planting. City parks will be planted in the spring and fall seasons to enhance canopy cover, provide shade, and improve biodiversity. These efforts will restore areas affected by Emerald Ash Borer, strengthen climate resilience, and create healthier, more enjoyable public spaces for the community. 

Each tree is carefully selected, mapped, and marked for planting in the field by a City arborist to ensure proper species placement and long-term success. Planting activities are carried out by a qualified contractor, and all newly planted trees are watered, maintained, and monitored for a minimum of two years to ensure healthy establishment and survival.

Keep an eye out for new tree planting in your park!

The City of Oshawa and Trees For Life have partnered in a five-year reforestation project under the 2 Billion Tree Program. The project will restore and enhance tree coverage in greenspaces, natural areas along creek corridors, and northern road corridors. Planting sites will help restore canopy throughout Oshawa that have been heavily impacted by extreme weather, disease, and an aging canopy. Native trees using current best practices, with dedicated Forestry staff overseeing planting, monitoring, and maintenance to ensure long-term survival. By focusing on diverse species and age groups, this initiative will help build a healthier, more resilient urban forest for the future.

Since 2018, the woodlot had experienced a steady decline because of Pine Wilt. Staff had responded to numerous service calls, including uprooted or fallen trees due to declining health, resulting in more than 100 tree removals. The trees posed a significant risk to park users and adjacent properties. To address concerns, the City undertook large-scale removal of the woodlot in late November 2021.
In 2022, 150 large caliper trees were planted to begin restoration efforts in this space. The woodlot will see a wide variety of native species planted throughout and create a more sustainable urban forest for the future.

Ongoing restoration

This has provided the City with a unique opportunity to increase biodiversity and resiliency. Scots pine is not native to Canada will take over an area by shading out native plant species, reducing biodiversity and habitat.
Restoration has included help from City staff, LEAF and volunteers. Over 1600 trees and shrubs have been planted to date and the area will continue to be planted and monitored by the City to ensure its success. Restoration will increase biodiversity, creating a more resilient forest. This will allow the woodlot to withstand the impacts of climate change, severe weather and damage caused by diseases and invasive species.

• 30 minute consultation in your yard with a LEAF arborist
• 5 to 8 foot tall native deciduous tree OR 2 to 4 foot tall native evergreen tree
• Delivery and full planting service
• Mulch and planting/care guide

• Online educational videos
• 30-minute virtual consultation with a LEAF arborist
• 5 to 8 foot tall native deciduous tree OR 2 to 4 foot tall native evergreen tree
• Delivery (property owner plants)
• Mulch and planting/care guide

Your new tree has been mulched in a “donut” or ring shape. This helps reduce weeds and retain soil moisture. You can add fresh mulch over the root ball area, but always keep mulch about 10 cm away from the trunk. (Free mulch is available at Oshawa Animal Services during the growing season.)
Avoid the mulch “volcano.”
Mounding mulch or soil against the trunk can harm your tree. Never cover or bury the trunk flare—the area where the trunk meets the roots. Improper mulching can cause:

• Moisture and decay at the tree base, inviting insects and pests
• Girdling or shallow roots that weaken the tree
• Less water reaching roots, limiting growth and establishment

Best Practices

• Use only mulch or other natural organic material around City-owned trees.
• Avoid landscape rings, brick borders, or landscape fabrics around the base of the tree. These can change soil grade and disrupt the tree’s natural environment and even cause tree decline or death.

You may notice green bags around newly planted trees in your neighbourhood. These are watering bags are used to give new trees a steady, slow release of water. This helps the soil stay moist longer and encourages strong, deep root growth.

Who fills them?

City staff and contractors regularly fill these bags during the growing season. However, during periods of heat or drought, new trees may need extra care. Homeowners are welcome—but not required—to fill the bags to help trees thrive.

Watering tips:

• If the soil is already very wet or water is pooling, wait before watering again.
• Keeping the soil evenly moist is best for healthy establishment.

How to use the water bag:

1. Lift the tag at the top to expose the fill opening.
2. Insert a garden hose and begin filling.
3. Gently lift the two black straps to allow the bottom of the bag to fully expand. (Note: Do not hang or suspend the bag by the straps.)
4. Fill the bag to the top. It will slowly drain over 5–9 hours.

Not all new trees need stakes, but in some cases, staking can help provide stability—especially in high winds, shallow soils, or if the root ball is loose after planting.

Stakes are a temporary support. Trees need to move naturally in the wind to develop strong trunks and “reaction wood,” which helps them withstand storms and other environmental stresses.

If staking is required, City staff will install it and remove the stakes within 1–2 years after planting.

Residents are not allowed to prune or otherwise alter any City tree By-law 63-2013. Tree maintenance is completed by the City on a ten-year cycle or by request. Submit any tree related requests to Service Oshawa or call 905-436-3311.

Keep lawn mowers and string trimmers away from the trunk, which can damage or even kill the tree if bark is removed around the trunk.

Tree guards have been installed on many new trees planted throughout parks and open spaces to help prevent unnecessary damage.

To grow a healthy mature tree canopy, the City is implementing several sustainable planting practices downtown aimed at improving growing conditions that include the:

• review of tree planting locations to limit conflicts with existing infrastructure, services and pedestrians;
• planting of suitable tree species tolerant to urban conditions;
• use of soil cell techniques and suspended paving to support the sidewalk above without compacting the soil below;
• use of rubberized mulch around the base of the tree to allow water to absorb into the soil; and
• installation of watering pipes to be used during times of drought.

• Do not trim or prune the tree. The City's forestry services has qualified arborists who will prune and maintain the trees as they mature.
• To avoid damaging the bark, which can eventually kill a tree, keep the area around the tree free of debris, do not lean, nail or attach anything to the trunks such as signs or bicycles.
• Leave the rubberized mulch at the base of the tree. The mulch is there to protect the tree from damage and reduce water loss.
• If you notice that a City boulevard or park trees is damaged or diseased, submit requests to Service Oshawa online Service Oshawa online. 

The emerald ash borer is an invasive beetle that feeds on all ash (fraxinus) species in Ontario, including green, red, white, black and blue ash, as well as some non-native species such as European black ash (fraxinus excelsior). Mountain ash is not a true ash tree and is not effected by the beetle.

The metallic green beetle emerges in early summer and will grow to be 8.5 to 13.5 mm long with a flattened head, large black compound eyes on the sides of the head, and short antennae. They lay 60 to 90 eggs one at a time in bark crevices on ash trees. Once the eggs hatch and become larvae, they tunnel under the bark to feed. These tunnels stop the flow of water and nutrients causing, the ash tree to die.

Identification

• Bark is tight, rough and often has a distinct diamond pattern
• The leaves are compound and contain five to eleven finely toothed leaflets
• The seeds of the leaf are oar shaped and hang down in clusters

Signs of infection

Signs of E.A.B. usually only become clear once a tree is heavily infested. However, the following are signs and symptoms your ash tree may be infested with the E.A.B.:

• leaves in the top third of the ash tree lose their green colour, thin and die back
• galleries girdle the ash trees and foliage will wilt or turn yellow
• branches begin to grow from the low trunk or roots
• shallow meandering “S” shaped tunnels under the bark with abrupt turns and “frass” (refuse left behind by boring insects) or sawdust will be evident in tunnels
• the bark begins to split
• there are small “D” shaped exit holes 4 to 5 mm across on the bark of infected trees
• increased woodpecker activity on the tree resulting in large holes

Lakeview Park and E.A.B.

• Lakeview Park has over 300 ash trees that are treated for E.A.B. every year by City staff
• The City uses a systemic insecticide called TreeAzin to treat Lakeview Park. It is approved by Health Canada's Pest Management Regulatory Agency. Trees showing signs of 30% or more dieback of their branches will not be treated
• Understory tree planting continues in the park to help offset canopy loss and create a more sustainable park canopy for the future.

Woodlots and green-spaces

While natural regeneration will account for most of the regrowth in our woodlands, portions of select sites have been identified for enhanced and/or intensive regeneration and replanting.

City trails and rural road right of way areas will be planted with small container stock trees as part of restoration planting and canopy enhancement. Replanting trees can provide: 

• Benefits to our health, the environment and the economy
• Improved air quality and provides habitat for wildlife
• Reduced heating and cooling costs of a home
• Increased property value

Private property

Please remember that private property owners are responsible for trees on their property. If you suspect your Ash tree may have E.A.B., you are encouraged to consult a professional arborist as soon as possible. You should choose an arborist certified with the International Society of Arboriculture or registered with the American Society of Consulting Arborists. Doing nothing may put you and your property at risk.

We encourage residents to also become stewards of our urban forest, which provides many environmental and ecological benefits and encourage all to consider planting more trees on their private property, where suitability exists.

Resources

• Ontario Ministry of Natural Resources
• Canadian Food Inspection Agency

Japanese Beetle are leaf skeletonizers, which eat the soft outer tissues of foliage while leaving behind a skeletal network of veins. When a tree is skeletonized, it does not mean it has died. A tree will often respond by producing new leaves by the end of the season. Japanese beetle is not a serious tree health concern unless infestations occur repeatedly and severely on the same tree.

The City will not put out traps for this insect. Although the pheromone and floral lures sold with the traps are very effective and attract many beetles each day, the traps attract more beetles than are caught. This results in other species of trees or plants being at risk of suffering damage from this insect.

Identification

• Spongy moth overwinters in the egg stage, often on the bark of trees
• Eggs hatch in the spring, and larvae ascend the trees to feed on the new foliage
• Feeding occurs during the day, but as the caterpillars mature, feeding occurs mainly at night
• Mature caterpillars are 50 mm long, dark coloured, hairy, with a double row of five pairs of blue spots, followed by a double row of six pairs of red spots
• Feeding finishes by August
• Male moths are light brown and slender-bodied, while females are white and heavy-bodied

Life cycle

The spongy moth has four distinct developmental stages in its life cycle similar to other moths and butterflies:

1. Eggs (late August to early May)

2. Caterpillar (early May to mid-July)|

3. Pupae or cocoon (mid-July to early August)

4. Moth (late July to late August)

Infestation

Spongy moth outbreaks can occur every seven to ten years.

• Caterpillars chew holes or devour entire leaves.
• In late July, you can find spongy egg masses on the trunks and branches of infected trees.
• During severe outbreaks, trees and shrubs are defoliated over large areas. Despite the trees' ability to produce a new crop of leaves in the same season, the damage can be harmful to the tree and makes it more susceptible to secondary pests, drought, or poor growing conditions.

Management tips

Visit the Government of Ontario website for best practices and management strategies when dealing with L.D.D. both in your community and on private property.

Frequently asked questions

Will the City spray for spongy moth?

• No. The City of Oshawa does not currently spray for spongy moth The City's integrated pest management (IPM) plan focuses on other strategies for management of pests and diseases that do not involve the use of pesticides.

What do I do if I see spongy moth?

• You can report sightings or infestations to Service Oshawa, or:

  • EDDMapS Ontario, 1-800-563-7711
  • Canada-wide: Invasive Species Centre

How can I help reduce the spongy moth population?

• CAUTION: Please ensure you are wearing proper hand protection when dealing with spongy moth as contact is known to cause skin irritation or allergic reactions.

My tree has been defoliated. Is it dead?

• No. Although the tree may have been defoliated, it is very unlikely to die. The tree will work to flush out a second set of foliage in the same season. Repeated defoliation can cause severe stress if sustained over many years. This could lead to the tree's decline; but it is rare for the tree to succumb to spongy moth in one season.

Tar spot is a fungal disease that does not harm the tree and only affects the appearance of the leaves. It begins as small yellow spots that become larger and turn black as the season progresses. To reduce or prevent this, rake up leaves and dispose of them immediately instead of placing them in a compost pile. The disease can over-winter on the ground in fallen leaves and is very hard to get completely remove from an area. 

Oak wilt was recently detected in Ontario and it is important to be aware of the signs and symptoms of the disease. It is a fungal disease spread naturally through root systems or by beetles carrying the fungal spores. Oak wilt is not a threat to humans or wildlife.

The City of Oshawa is following the recommendation of the C.F.I.A. (Canadian Food Inspection Agency) and I.S.A.O. (International Society of Arboriculture Ontario) and will not be pruning any oak species from April to November as a precaution. If pruning must be done outside this time frame, cuts will be painted with wound dressing.

What can you do?

• Do not prune or wound oak trees between April and November
• Do not move firewood (of any species)
• Report suspected oak wilt to the C.F.I.A.

For more details and information on the signs and symptoms of this disease please visit any of the following links:

• Canadian Food Inspection Agency (C.F.I.A.)
• International Society of Arboriculture Ontario (I.S.A.O.)
• Invasive Species Centre