A wildflower meadow and a row of young trees have been destroyed "by mistake" by a contractor working for a council.
Hundreds of poppies, primroses, meadow buttercups and 100 saplings at Manor Farm Orchard in Kingsway, Gloucester, were mown down.
They had been planted last November by volunteers to encourage wildlife and improve the environment.
Gloucester City Council and contractor Amey has apologised and launched an investigation into how it happened.
Sarah Ottaway, chair of the Kingsway Wildlife and Sustainability Group, said it was "devastating" that "everyone's hard work had gone to waste".
She said the "lovely wildflowers", including cornflowers and poppies, "looked wonderful" and they were "all taken down in their prime".
"It was a surprise because the area has been mowed before and the trees have been absolutely fine.
"We think there has been some sort of miscommunication."
An Amey spokesperson said vegetation in some areas was cut back at this time of year "so they do not become overgrown and encourage fly-tipping or antisocial behaviour".
"The council have informed us of reports that some wildflowers may have been accidentally destroyed in the process.
"We are investigating this but we are sorry if this is what has happened."
Councillor Richard Cook, who helped with the planting, said he was "disappointed", and believed it happened because the grass had grown longer than normal due to the recent warm and wet weather.