Our Forestry Practices

We believe that how we do our work is as important as the work itself.
photo of a Hydro One Forestry worker doing tree trimming from a bucket

With over 150,000 kilometres of transmission and distribution power lines, we maintain them through a preventative approach of vegetation management work on a six to eight-year cycle. These practices have been developed to determine the best methods to keep our power lines and equipment clear from potential hazards, helping to ensure a reliable supply of electricity to your homes and businesses.

We have the largest electricity distribution and transmission service territory in Ontario, with diverse wildlife, tree species, and terrain. We always take into consideration the indigenous species, growth habits, tree health, invasive species, and species at risk, as well as geography and individual line voltage to make the best decisions for our customers and the local environment.

Compatible and Incompatible Vegetation

We maintain vegetation growing on or beside right-of-ways beneath our power lines. We promote the growth of the type of vegetation defined as Compatible Vegetation. Compatible Vegetation rarely grows to a height that would interfere with the safe operation of our power lines. Incompatible vegetation includes any plant or tree species that could grow within the required clearance area.

Our practices may include any of the following methods:

  • Removing incompatible vegetation, such as trees and brush from right-of-ways 

  • Trimming or pruning branches of surrounding trees to meet clearance standards

  • Removing vegetation that could interfere with access to right-of-ways in an emergency

  • Removing trees that could interfere with the safe and reliable delivery of electricity

  • Clearing rights-of-ways and re-seeding areas with a compatible ground cover mixture

  • Selectively applying herbicide, if agreed to by the landowner, to prevent re-growth.

For more information, visit Caring for Your Property.

Did You Know?

A tree on a right-of-way in Ohio came into contact with a power line and caused a widespread blackout in August 2003. A North American Electric Reliability Corporation (NERC) investigation following the blackout, which affected both Canada and the United States, discovered the blackout would have never occurred if the company that owned the power line had properly maintained its right-of-way.

Environmental Practices and Preservation


In many cases, trimming certain species of plants can encourage more stems to sprout from the established root system. This can increase the density and amount of vegetation over time.

To help prevent this and encourage the growth of other low growing vegetation, we endeavour to treat plants with a low volume, direct application herbicide that is federally and provincially approved.

Right-of-ways have been maintained by selectively treating vegetation with herbicides to promote the growth of low-growing plant communities. This vegetation provides excellent habitat for small animals, controls erosion, and becomes a natural deterrent to the growth of undesirable vegetation.

Before applying herbicides on private property, we seek permission from the landowner and municipal authorities. Herbicides are applied by our forestry professionals who are properly licensed, certified, and supervised in accordance with provincial rules, regulations, internal standards, and pesticide-specific applications.

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Species at Risk

Our team follows all laws and regulations for endangered, threatened, special concern, and extirpated animals and plants in Ontario.  This includes Ontario’s Endangered Species Act and the Federal Species at Risk Act, which applies to federal land or water in Ontario. We have worked with the Ministry of Natural Resources and Forestry when dealing with species at risk.

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Invasive Plants & Insects

Our practices aim to control the spread of invasive plant and insect species. This effort is done in cooperation with local conservation authorities, municipalities, and Federal Agencies. We have a partnership with the Ontario Invasive Plant Council to help prevent and manage invasive species.

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We take pride in our environmental commitment and responsibilities, and have several biodiversity initiatives. In 2015, we supported the David Suzuki Foundation’s Got Milkweed campaign, which supported the planting of more than 15,000 milkweed and pollinator-friendly plants.