Stay safe when pruning your trees

Man pruning a tree with a chainsaw full width

More than half of all electricity outages in B.C. are caused by trees. Distribution lines, which provide power to homes and businesses, and are usually found along roads in urban areas, and transmission lines (larger, higher voltage lines that take electricity from generating stations to substations) can both be affected by branches and trees. But damage from falling branches and toppling trees can be prevented with some regular maintenance.

John Monk is one of BC Hydro’s experts when it comes to maintaining trees and plants. For homeowners pruning trees or shrubs in their yards, or along their road frontages, he says that early spring is a good time to trim. “You want to prune before the buds swell on a tree,” he explains on the phone.  However, BC Hydro conducts pruning year-round due to the vast number of trees growing next to power lines.

Pruning promotes flowering and new growth, and Canadian Gardening recommends that trees and shrubs be pruned to get rid of dead wood and unwanted development.

Where possible, shrubs that flower in the spring should be pruned immediately after they bloom. And those that bloom in the summer or early fall can be pruned in the spring, just as growth is about to start.

You can remove weak, diseased, or dead branches from trees at any time during the year. But most trees benefit from being pruned in the early spring, just before the seasonal spurt begins.

Pruning large trees can be dangerous, so consider hiring a professional arborist. They can determine the best approach to improve the health, appearance, and safety of your tree.

John works in the Surrey, Delta, Tsawwassen areas of the Fraser Valley maintaining vegetation around distribution lines and is often asked for advice. “As the weather improves, a lot of people are thinking about pruning their trees,” he says. John can advise some customers on the phone, but others he visits in person.

John not only advises BC Hydro customers. He also consults with BC Hydro line crews and other arborists.

If a tree is near a power line, call a professional

You can plant trees near power lines, as long as the mature height of the tree is under six metres for distribution lines, and under three metres for transmission lines. The lines found in most urban areas and residential neighbourhoods are usually distribution lines; transmission lines carry power to substations and large business customers.

If you’ve got a tall tree within 10 metres of a power line, however, it should be monitored and pruned regularly. A tree may have to be removed if it is hazardous, or if it poses a threat of contacting, growing into or falling on a power line.  Please contact BC Hydro for assistance if you have concerns about a tree growing closer than 10 metres to a power line. If the tree is growing within 10 metres of the power line, BC Hydro will arrange and contract the work.

You should never prune trees yourself if they are within 10 metres of a power line. “If it’s something you can’t do with a stepladder,” says John, “contact a professional”.  Working around energized power lines requires Certified Utility Arborists to perform the work. These professionals are highly skilled and trained to work near power lines.

That’s because trees can conduct electricity, especially if they are wet. And electricity can arc, meaning that under the right conditions, it can jump across gaps.

Professional arborists, says John, can prune trees that may be close to the service power lines that go to your house. “Good contractors will recommend when BC Hydro needs to get involved,” he adds.

If you use a ladder, use it properly

Ladders can also conduct electricity if they come into contact with a power line (the paint on wooden ladders is often the culprit), so use them with care.  Aluminium ladders are not recommended for use near power lines.

And refer to the annotated diagram from for additional tips on how to use ladders safely.

When BC Hydro takes care of the pruning

BC Hydro regularly inspects trees and other tall plants that grow near power lines and transformers. They have a work schedule for trees that have been identified as at risk for growing or falling into power lines.

Professionals like John, who are skilled at maintaining healthy trees and plants, identify and coordinate any pruning or removal work that needs to be done close to power lines.

The process of topping a tree, removing a major portion of the top of the tree, results in an unhealthy plant. For one thing, topping causes too much growth of weak branches the following year. Topping also leads to portions of the root system dying off because there aren’t enough leaves to sustain them. A topped tree ends up weak and unstable.

“Thirty years ago,” says John, “topping was common practice. But the science of caring and maintaining for trees has evolved considerably since then. Today, trees can be reduced in size and volume without any harm to the plant.

Managing hazardous trees

Trees with disease, flaws, or other weaknesses are more likely to fall than others. In these instances, pruning may not be enough and the tree might need to be removed.

John knows which trees in his region need to be monitored, and he has a computer program that helps him keep track of potential hazards.

If a hazardous tree is located near or on your property, BC Hydro will get in touch to let you know and to discuss what needs to be done. BC Hydro will then assist with the removal.  If you notice a tree that is flawed, dead, dying or leaning towards the power line, please contact BC Hydro for assistance.