The pollarding operation is taking place this week in East Street, Osney Island.
Staff working for Complete Tree Services are thought to be carrying out the work on behalf of Oxford Direct Services, which carries out a wide range of work for Oxford City Council.
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Trees surgeons also carried out the pollarding in 2019.
The pruning process involves dead branches and leaves being removed to ensure the long-term overall health of the tree.
The city council has been asked for comment.
A spokesman said in 2019: “These willow trees have historically undergone the practice of pollarding.
“Once this cycle has begun, it is important to regularly maintain these to the previous pruning points as branches can grow back weaker.
“The work currently being undertaken is based on the health and safety implications in the trees’ surroundings.
Craig Blood pollarding trees in Oxford (Image: Andy Ffrench)
“Oxford Direct Services has undertaken consultation with local ward councillors and nearby residents, who have been made aware that these works were required.”
In 2006 families on Osney Island lost a battle to save 12 willow trees lining the river in the street. Council officials said it was a safety issue.
There have apparently been no protests so far this year.
Pollarding in Oxford (Image: Andy Ffrench)
A resident who lives nearby on a narrowboat on the Thames said: “The street will certainly be a lot lighter when this work is completed.
“And East Street does have an issue with all the leaves falling onto the road.
“I think the contractors used to have a system of cutting back alternate trees but they don’t do that now – possibly for cost reasons.”
A member of the team working in East Street said the work was carried out every few years for safety reasons.