Selecting a Tree with Power Lines in Mind

If you are thinking about planting a tree or a shrub on your property, it is just as important to consider what you are going to plant as it is to decide where you are going to plant it. The right tree or shrub, planted in the right place, can provide years of beauty and add value to your property. Taking the time to plan will reduce the chance that your new tree will grow too close to a power line and have to be severely pruned, or removed altogether.

A tree that is planted in the right place will be able to grow as nature intended it, with the shape, size and height that you expect. A tree that is planted too close to a power line or hydro pole can cause a range of potential disruptions to the power supply. Trees that are growing too close to poles or lines must be pruned and it is possible that, if planted in the wrong place, Oakville Hydro may have to be prune the tree in order to maintain a safe, reliable electrical service.

Please follow the guidelines, below. If you are still unsure about where you want to plant trees and shrubs on your property, please call Oakville Hydro at 905-825-9400, extension 5274 for assistance. You must also contact Ontario One Call at 1-800-400-2255 or to locate any possible underground wires or other underground utilities that may be in your way before you dig the hole for the tree you are about to plant.

Trees to Consider

To help you decide which tree is right for your yard, here are a few suggestions:

Small Trees
The following small trees (maximum height 4.5 metres) grow well in southern Ontario and can be planted directly underneath power lines without future worries about

Amur Maple
Japanese Maple
Medium Trees
The following medium-sized trees (mature height between 7.5 to 12 metres) can be planted as long as they are located at least 12 metres away from below a power line to avoid the need for future pruning:

Crab Apple
Ornamental Pear
White Cedar
Large Trees
 Large trees, such as oaks, often spread out considerably as they grow. Plant large-growing species (mature height 12 metres or more) at least 16 metres from below the power lines to avoid the need for future pruning:

Blue Spruce          Red Oak
White Oak             Sugar Maple
Red Maple            White Pine

Planting Trees Near Distribution Lines

Different types of power lines require different clearances:

Single-phase lines require a minimum clearance of three (3) metres on each side and under the power line. This clearance requires the removal of any overhanging branches – live, dead or structurally weak – as seen in the diagram above.

Two and three-phase lines require a minimum clearance of three (3) metres on each side and under the nearest power line. This clearance requires the removal of any overhanging and/or invading limbs or branches above the power line.

Tree Maintenance  and Your Safety

Oakville Hydro must remove brush and prune trees near power lines in order to provide safe and reliable service to all of our customers. We are also legally required, through the Electrical Safety Authority of Ontario and Ontario’s Electricity Act, to prune trees and plants growing near power lines. We also maintain trees that grow on Oakville Hydro property around all electric substations in the Town of Oakville.

If any part of a power line is wholly within private property, then the pruning costs of trees near that line are the responsibility of the property owner. Consequently, we recommend that property owners carry out annual tree inspections (i.e., those trees on private property and not in an Oakville Hydro easement) at least once a year.

If trees on private property require pruning, property owners should be mindful of the location of power lines before pruning begins. The Electricity Act requires anyone working or lifting within three metres of overhead power lines or poles to contact their local distribution company for assistance. In Oakville - that’s us, Oakville Hydro. Serious injury, even death, can result if you come into contact with a power line during routine tree maintenance. We can create a safe work environment for you or your contractor to prune trees, or for your electrician to access power lines.

The following diagrams show the best way to prune trees around power lines and poles:

Side Pruning
Cut back or remove side branches threatening the conductors.
Under Pruning
Remove limbs beneath the tree crown to allow wires to pass below the tree canopy.
Through Pruning
Remove branches within the crown to allow lines to pass through the tree. This method is best suited for house service secondary wires and other coated wires

Shrubs and Transformers

If you are considering planting shrubbery around a pad-mounted transformer (the rectangular green boxes located near property lines), please note the need to keep as much open space as possible so hydro crews can get inside the transformer for repairs and maintenance. Property owners are encouraged not to plant any vegetation other than turf grasses within 3.65 metres of the opening side of the box (where the padlock is located), as noted in Figure #1 below. A clearance of three (3) metres is required at all times on this side of the transformer.


Transformer Safety

If there is a transformer on or near your property line, please note the following safety tips:

  • Always call Ontario One Call at least seven business days before you plan to dig at 1-800-400-2255 or visit their website, One of their representatives will visit your property to locate and identify existing buried conductors around the transformer.
  • Keep all shrubs, fences and other permanent structures at least three metres from the front and one (1) metre from the back and sides of the transformer (see Figure #1 above).
  • Don't plant trees near pad-mounted transformers! A tree's large root system could lift the concrete pad and potentially create a power outage.
  • Select plants that are slow growing and easy to maintain. Avoid using plants with thorns, such as barberry, blackberry, hawthorne or roses.
  • Don't over plant – use a few properly selected plants.
  • Location numbers and/or company locks must be visible at all times (see Figure #2 above).
  • Don't allow plants to overgrow the transformer. Valuable equipment can overheat and become damaged, possibly causing a power interruption.
  • Don't plant vines or ivy, which can attach to and potentially damage the transformer.
  • Don't place dirt, wood chips or snow against any portion of the transformer – this could also cause it to overheat and/or rust prematurely.
  • Don't change grade levels around the pad-mounted transformer for a distance of 1.8 metres out from the cement base of the transformer.

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