Glendale has won a three-year arboriculture framework contract to prevent overgrown or fallen trees causing power failures along electricity power lines.
The deal with SP Energy Networks, which distributes electricity to 3.3 million customers across the north of England, Wales and parts of Scotland, will require tree gangs to undertake safety cutting and clearance in Wales from 1 January.
There are more than 238,000km of electricity power lines spanning the UK. A fifth of all power outages are caused by trees and vegetation management along power lines, transmission towers and substations is a legal requirement.
The company said: "Glendale's experienced teams have been delivering these specialist utility solutions for the past 18 years. As part of the framework agreement, Glendale staff will carry out detailed arboricultural surveys.
"This will involve assessing work required and seeking permissions for any work that needs to be done on private land. Glendale will then undertake felling, thinning and reductions in line with the surveyor's assessment."
A spokeswoman added that all works would be delivered through Glendale's ISO90001 quality management system and will meet PAS 55 protocol.