Isabel Mackenzie chained herself to the river red gum on the side of the Western Highway near Buangor, 74 kilometres west of Ballarat, about 7am on Monday.

Trees are being knocked down along the highway for it to be widened and Mrs Mackenzie said she was protesting to "bring attention to the devastation that's being wrought."

"I think more consideration should be given to the vegetation in the area," she said.

"These are trees that are hundreds of years old."

Mrs Mackenzie said she would stay chained to the tree for as long as seemed necessary and had been encouraged to continue her first ever protest by passing motorists, who had been honking their horns in support.

"I'm normally a very a peaceful citizen," the grandmother and local resident of 60 years said.

Helen Lewers, who is chained to the tree with Mrs Mackenzie, said VicRoads should reroute the highway between Buangor and Stawell to preserve the native roadside vegetation.

Police are at the scene and roadwork has been suspended.

This story Grandmother, 91, chains herself to tree in Victoria's west to protest roadworks first appeared on The Age website.