Thomson, previously general manager at Glendale, will oversee the company’s utility arboriculture work in the south-west and Midlands regions.
Managing director Andy Corcoran said: “James’ promotion meets our strategic aim to advance our existing staff.
“It reaffirms Glendale’s intention to provide ongoing training and development to ensure our staff are the first choice when promotion opportunities arise.
“Our growth in the number of employees, assets and sales means it is necessary to strengthen our senior management team.
“I am delighted to be able to do this from within the company. James’ commitment and performance mean he was our first choice.”
Glendale has arboriculture teams across the UK which provide 24-hour emergency tree services, 365 days a year.